#37745

Committed 11 Apr 2024 03:54AM UTC coverage: 87.241% (+5.8%) from 81.402%

Build # #37745

Build Type

push

local

Committed by

web-flow

Commit Message

Fix comparison base for line table compression (#54032)

I'm not entirely sure what the original intent of this statement was,
but the effect ends up being that some codeloc entries end up negative
in the compressed representation, but the code always assumes unsigned
integers, so things roundtripped badly, leading to badly corrupted stack
traces. I guess this might have been a rebase mistake,
since the same line exists (correctly) a few lines prior. Fixes #54031.

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79.2

/stdlib/REPL/src/REPL.jl

# This file is a part of Julia. License is MIT: https://julialang.org/license

"""
Run Evaluate Print Loop (REPL)

Example minimal code

```julia
import REPL
term = REPL.Terminals.TTYTerminal("dumb", stdin, stdout, stderr)
repl = REPL.LineEditREPL(term, true)
REPL.run_repl(repl)
```
"""
module REPL

Base.Experimental.@optlevel 1
Base.Experimental.@max_methods 1

function UndefVarError_hint(io::IO, ex::UndefVarError)
    var = ex.var
    if var === :or
        print(io, "\nSuggestion: Use `||` for short-circuiting boolean OR.")
    elseif var === :and
        print(io, "\nSuggestion: Use `&&` for short-circuiting boolean AND.")
    elseif var === :help
        println(io)
        # Show friendly help message when user types help or help() and help is undefined
        show(io, MIME("text/plain"), Base.Docs.parsedoc(Base.Docs.keywords[:help]))
    elseif var === :quit
        print(io, "\nSuggestion: To exit Julia, use Ctrl-D, or type exit() and press enter.")
    end
    if isdefined(ex, :scope)
        scope = ex.scope
        if scope isa Module
            bnd = ccall(:jl_get_module_binding, Any, (Any, Any, Cint), scope, var, true)::Core.Binding
            if isdefined(bnd, :owner)
                owner = bnd.owner
                if owner === bnd
                    print(io, "\nSuggestion: add an appropriate import or assignment. This global was declared but not assigned.")
                end
            else
                owner = ccall(:jl_binding_owner, Ptr{Cvoid}, (Any, Any), scope, var)
                if C_NULL == owner
                    # No global of this name exists in this module.
                    # This is the common case, so do not print that information.
                    # It could be the binding was exported by two modules, which we can detect
                    # by the `usingfailed` flag in the binding:
                    if isdefined(bnd, :flags) && Bool(bnd.flags >> 4 & 1) # magic location of the `usingfailed` flag
                        print(io, "\nHint: It looks like two or more modules export different ",
                              "bindings with this name, resulting in ambiguity. Try explicitly ",
                              "importing it from a particular module, or qualifying the name ",
                              "with the module it should come from.")
                    else
                        print(io, "\nSuggestion: check for spelling errors or missing imports.")
                    end
                    owner = bnd
                else
                    owner = unsafe_pointer_to_objref(owner)::Core.Binding
                end
            end
            if owner !== bnd
                # this could use jl_binding_dbgmodule for the exported location in the message too
                print(io, "\nSuggestion: this global was defined as `$(owner.globalref)` but not assigned a value.")
            end
        elseif scope === :static_parameter
            print(io, "\nSuggestion: run Test.detect_unbound_args to detect method arguments that do not fully constrain a type parameter.")
        elseif scope === :local
            print(io, "\nSuggestion: check for an assignment to a local variable that shadows a global of the same name.")
        end
    else
        scope = undef
    end
    if scope !== Base && !_UndefVarError_warnfor(io, Base, var)
        warned = false
        for m in Base.loaded_modules_order
            m === Core && continue
            m === Base && continue
            m === Main && continue
            m === scope && continue
            warned |= _UndefVarError_warnfor(io, m, var)
        end
        warned ||
            _UndefVarError_warnfor(io, Core, var) ||
            _UndefVarError_warnfor(io, Main, var)
    end
    return nothing
end

function _UndefVarError_warnfor(io::IO, m::Module, var::Symbol)
    Base.isbindingresolved(m, var) || return false
    (Base.isexported(m, var) || Base.ispublic(m, var)) || return false
    print(io, "\nHint: a global variable of this name also exists in $m.")
    return true
end

function __init__()
    Base.REPL_MODULE_REF[] = REPL
    Base.Experimental.register_error_hint(UndefVarError_hint, UndefVarError)
    return nothing
end

using Base.Meta, Sockets, StyledStrings
import InteractiveUtils

export
    AbstractREPL,
    BasicREPL,
    LineEditREPL,
    StreamREPL

import Base:
    AbstractDisplay,
    display,
    show,
    AnyDict,
    ==

_displaysize(io::IO) = displaysize(io)::Tuple{Int,Int}

include("Terminals.jl")
using .Terminals

abstract type AbstractREPL end

include("options.jl")

include("LineEdit.jl")
using .LineEdit
import ..LineEdit:
    CompletionProvider,
    HistoryProvider,
    add_history,
    complete_line,
    history_next,
    history_next_prefix,
    history_prev,
    history_prev_prefix,
    history_first,
    history_last,
    history_search,
    setmodifiers!,
    terminal,
    MIState,
    PromptState,
    mode_idx

include("REPLCompletions.jl")
using .REPLCompletions

include("TerminalMenus/TerminalMenus.jl")
include("docview.jl")

@nospecialize # use only declared type signatures

answer_color(::AbstractREPL) = ""

const JULIA_PROMPT = "julia> "
const PKG_PROMPT = "pkg> "
const SHELL_PROMPT = "shell> "
const HELP_PROMPT = "help?> "

mutable struct REPLBackend
    "channel for AST"
    repl_channel::Channel{Any}
    "channel for results: (value, iserror)"
    response_channel::Channel{Any}
    "flag indicating the state of this backend"
    in_eval::Bool
    "transformation functions to apply before evaluating expressions"
    ast_transforms::Vector{Any}
    "current backend task"
    backend_task::Task

    REPLBackend(repl_channel, response_channel, in_eval, ast_transforms=copy(repl_ast_transforms)) =
        new(repl_channel, response_channel, in_eval, ast_transforms)
end
REPLBackend() = REPLBackend(Channel(1), Channel(1), false)

"""
    softscope(ex)

Return a modified version of the parsed expression `ex` that uses
the REPL's "soft" scoping rules for global syntax blocks.
"""
function softscope(@nospecialize ex)
    if ex isa Expr
        h = ex.head
        if h === :toplevel
            ex′ = Expr(h)
            map!(softscope, resize!(ex′.args, length(ex.args)), ex.args)
            return ex′
        elseif h in (:meta, :import, :using, :export, :module, :error, :incomplete, :thunk)
            return ex
        elseif h === :global && all(x->isa(x, Symbol), ex.args)
            return ex
        else
            return Expr(:block, Expr(:softscope, true), ex)
        end
    end
    return ex
end

# Temporary alias until Documenter updates
const softscope! = softscope

const repl_ast_transforms = Any[softscope] # defaults for new REPL backends

# Allows an external package to add hooks into the code loading.
# The hook should take a Vector{Symbol} of package names and
# return true if all packages could be installed, false if not
# to e.g. install packages on demand
const install_packages_hooks = Any[]

# N.B.: Any functions starting with __repl_entry cut off backtraces when printing in the REPL.
# We need to do this for both the actual eval and macroexpand, since the latter can cause custom macro
# code to run (and error).
__repl_entry_lower_with_loc(mod::Module, @nospecialize(ast), toplevel_file::Ref{Ptr{UInt8}}, toplevel_line::Ref{Cint}) =
    ccall(:jl_expand_with_loc, Any, (Any, Any, Ptr{UInt8}, Cint), ast, mod, toplevel_file[], toplevel_line[])
__repl_entry_eval_expanded_with_loc(mod::Module, @nospecialize(ast), toplevel_file::Ref{Ptr{UInt8}}, toplevel_line::Ref{Cint}) =
    ccall(:jl_toplevel_eval_flex, Any, (Any, Any, Cint, Cint, Ptr{Ptr{UInt8}}, Ptr{Cint}), mod, ast, 1, 1, toplevel_file, toplevel_line)

function toplevel_eval_with_hooks(mod::Module, @nospecialize(ast), toplevel_file=Ref{Ptr{UInt8}}(Base.unsafe_convert(Ptr{UInt8}, :REPL)), toplevel_line=Ref{Cint}(1))
    if !isexpr(ast, :toplevel)
        ast = __repl_entry_lower_with_loc(mod, ast, toplevel_file, toplevel_line)
        check_for_missing_packages_and_run_hooks(ast)
        return __repl_entry_eval_expanded_with_loc(mod, ast, toplevel_file, toplevel_line)
    end
    local value=nothing
    for i = 1:length(ast.args)
        value = toplevel_eval_with_hooks(mod, ast.args[i], toplevel_file, toplevel_line)
    end
    return value
end

function eval_user_input(@nospecialize(ast), backend::REPLBackend, mod::Module)
    lasterr = nothing
    Base.sigatomic_begin()
    while true
        try
            Base.sigatomic_end()
            if lasterr !== nothing
                put!(backend.response_channel, Pair{Any, Bool}(lasterr, true))
            else
                backend.in_eval = true
                for xf in backend.ast_transforms
                    ast = Base.invokelatest(xf, ast)
                end
                value = toplevel_eval_with_hooks(mod, ast)
                backend.in_eval = false
                setglobal!(Base.MainInclude, :ans, value)
                put!(backend.response_channel, Pair{Any, Bool}(value, false))
            end
            break
        catch err
            if lasterr !== nothing
                println("SYSTEM ERROR: Failed to report error to REPL frontend")
                println(err)
            end
            lasterr = current_exceptions()
        end
    end
    Base.sigatomic_end()
    nothing
end

function check_for_missing_packages_and_run_hooks(ast)
    isa(ast, Expr) || return
    mods = modules_to_be_loaded(ast)
    filter!(mod -> isnothing(Base.identify_package(String(mod))), mods) # keep missing modules
    if !isempty(mods)
        isempty(install_packages_hooks) && Base.require_stdlib(Base.PkgId(Base.UUID("44cfe95a-1eb2-52ea-b672-e2afdf69b78f"), "Pkg"))
        for f in install_packages_hooks
            Base.invokelatest(f, mods) && return
        end
    end
end

function _modules_to_be_loaded!(ast::Expr, mods::Vector{Symbol})
    ast.head === :quote && return mods # don't search if it's not going to be run during this eval
    if ast.head === :using || ast.head === :import
        for arg in ast.args
            arg = arg::Expr
            arg1 = first(arg.args)
            if arg1 isa Symbol # i.e. `Foo`
                if arg1 != :. # don't include local imports
                    push!(mods, arg1)
                end
            else # i.e. `Foo: bar`
                push!(mods, first((arg1::Expr).args))
            end
        end
    end
    if ast.head !== :thunk
        for arg in ast.args
            if isexpr(arg, (:block, :if, :using, :import))
                _modules_to_be_loaded!(arg, mods)
            end
        end
    else
        code = ast.args[1]
        for arg in code.code
            isa(arg, Expr) || continue
            _modules_to_be_loaded!(arg, mods)
        end
    end
end

function modules_to_be_loaded(ast::Expr, mods::Vector{Symbol} = Symbol[])
    _modules_to_be_loaded!(ast, mods)
    filter!(mod::Symbol -> !in(mod, (:Base, :Main, :Core)), mods) # Exclude special non-package modules
    return unique(mods)
end

"""
    start_repl_backend(repl_channel::Channel, response_channel::Channel)

    Starts loop for REPL backend
    Returns a REPLBackend with backend_task assigned

    Deprecated since sync / async behavior cannot be selected
"""
function start_repl_backend(repl_channel::Channel{Any}, response_channel::Channel{Any}
                            ; get_module::Function = ()->Main)
    # Maintain legacy behavior of asynchronous backend
    backend = REPLBackend(repl_channel, response_channel, false)
    # Assignment will be made twice, but will be immediately available
    backend.backend_task = @async start_repl_backend(backend; get_module)
    return backend
end

"""
    start_repl_backend(backend::REPLBackend)

    Call directly to run backend loop on current Task.
    Use @async for run backend on new Task.

    Does not return backend until loop is finished.
"""
function start_repl_backend(backend::REPLBackend,  @nospecialize(consumer = x -> nothing); get_module::Function = ()->Main)
    backend.backend_task = Base.current_task()
    consumer(backend)
    repl_backend_loop(backend, get_module)
    return backend
end

function repl_backend_loop(backend::REPLBackend, get_module::Function)
    # include looks at this to determine the relative include path
    # nothing means cwd
    while true
        tls = task_local_storage()
        tls[:SOURCE_PATH] = nothing
        ast, show_value = take!(backend.repl_channel)
        if show_value == -1
            # exit flag
            break
        end
        eval_user_input(ast, backend, get_module())
    end
    return nothing
end

struct REPLDisplay{Repl<:AbstractREPL} <: AbstractDisplay
    repl::Repl
end

function display(d::REPLDisplay, mime::MIME"text/plain", x)
    x = Ref{Any}(x)
    with_repl_linfo(d.repl) do io
        io = IOContext(io, :limit => true, :module => active_module(d)::Module)
        if d.repl isa LineEditREPL
            mistate = d.repl.mistate
            mode = LineEdit.mode(mistate)
            if mode isa LineEdit.Prompt
                LineEdit.write_output_prefix(io, mode, get(io, :color, false)::Bool)
            end
        end
        get(io, :color, false)::Bool && write(io, answer_color(d.repl))
        if isdefined(d.repl, :options) && isdefined(d.repl.options, :iocontext)
            # this can override the :limit property set initially
            io = foldl(IOContext, d.repl.options.iocontext, init=io)
        end
        show(io, mime, x[])
        println(io)
    end
    return nothing
end
display(d::REPLDisplay, x) = display(d, MIME("text/plain"), x)

function print_response(repl::AbstractREPL, response, show_value::Bool, have_color::Bool)
    repl.waserror = response[2]
    with_repl_linfo(repl) do io
        io = IOContext(io, :module => active_module(repl)::Module)
        print_response(io, response, show_value, have_color, specialdisplay(repl))
    end
    return nothing
end

function repl_display_error(errio::IO, @nospecialize errval)
    # this will be set to true if types in the stacktrace are truncated
    limitflag = Ref(false)
    errio = IOContext(errio, :stacktrace_types_limited => limitflag)
    Base.invokelatest(Base.display_error, errio, errval)
    if limitflag[]
        print(errio, "Some type information was truncated. Use `show(err)` to see complete types.")
        println(errio)
    end
    return nothing
end

function print_response(errio::IO, response, show_value::Bool, have_color::Bool, specialdisplay::Union{AbstractDisplay,Nothing}=nothing)
    Base.sigatomic_begin()
    val, iserr = response
    while true
        try
            Base.sigatomic_end()
            if iserr
                val = Base.scrub_repl_backtrace(val)
                Base.istrivialerror(val) || setglobal!(Base.MainInclude, :err, val)
                repl_display_error(errio, val)
            else
                if val !== nothing && show_value
                    try
                        if specialdisplay === nothing
                            Base.invokelatest(display, val)
                        else
                            Base.invokelatest(display, specialdisplay, val)
                        end
                    catch
                        println(errio, "Error showing value of type ", typeof(val), ":")
                        rethrow()
                    end
                end
            end
            break
        catch ex
            if iserr
                println(errio) # an error during printing is likely to leave us mid-line
                println(errio, "SYSTEM (REPL): showing an error caused an error")
                try
                    excs = Base.scrub_repl_backtrace(current_exceptions())
                    setglobal!(Base.MainInclude, :err, excs)
                    repl_display_error(errio, excs)
                catch e
                    # at this point, only print the name of the type as a Symbol to
                    # minimize the possibility of further errors.
                    println(errio)
                    println(errio, "SYSTEM (REPL): caught exception of type ", typeof(e).name.name,
                            " while trying to handle a nested exception; giving up")
                end
                break
            end
            val = current_exceptions()
            iserr = true
        end
    end
    Base.sigatomic_end()
    nothing
end

# A reference to a backend that is not mutable
struct REPLBackendRef
    repl_channel::Channel{Any}
    response_channel::Channel{Any}
end
REPLBackendRef(backend::REPLBackend) = REPLBackendRef(backend.repl_channel, backend.response_channel)

function destroy(ref::REPLBackendRef, state::Task)
    if istaskfailed(state)
        close(ref.repl_channel, TaskFailedException(state))
        close(ref.response_channel, TaskFailedException(state))
    end
    close(ref.repl_channel)
    close(ref.response_channel)
end

"""
    run_repl(repl::AbstractREPL)
    run_repl(repl, consumer = backend->nothing; backend_on_current_task = true)

    Main function to start the REPL

    consumer is an optional function that takes a REPLBackend as an argument
"""
function run_repl(repl::AbstractREPL, @nospecialize(consumer = x -> nothing); backend_on_current_task::Bool = true, backend = REPLBackend())
    backend_ref = REPLBackendRef(backend)
    cleanup = @task try
            destroy(backend_ref, t)
        catch e
            Core.print(Core.stderr, "\nINTERNAL ERROR: ")
            Core.println(Core.stderr, e)
            Core.println(Core.stderr, catch_backtrace())
        end
    get_module = () -> active_module(repl)
    if backend_on_current_task
        t = @async run_frontend(repl, backend_ref)
        errormonitor(t)
        Base._wait2(t, cleanup)
        start_repl_backend(backend, consumer; get_module)
    else
        t = @async start_repl_backend(backend, consumer; get_module)
        errormonitor(t)
        Base._wait2(t, cleanup)
        run_frontend(repl, backend_ref)
    end
    return backend
end

## BasicREPL ##

mutable struct BasicREPL <: AbstractREPL
    terminal::TextTerminal
    waserror::Bool
    frontend_task::Task
    BasicREPL(t) = new(t, false)
end

outstream(r::BasicREPL) = r.terminal
hascolor(r::BasicREPL) = hascolor(r.terminal)

function run_frontend(repl::BasicREPL, backend::REPLBackendRef)
    repl.frontend_task = current_task()
    d = REPLDisplay(repl)
    dopushdisplay = !in(d,Base.Multimedia.displays)
    dopushdisplay && pushdisplay(d)
    hit_eof = false
    while true
        Base.reseteof(repl.terminal)
        write(repl.terminal, JULIA_PROMPT)
        line = ""
        ast = nothing
        interrupted = false
        while true
            try
                line *= readline(repl.terminal, keep=true)
            catch e
                if isa(e,InterruptException)
                    try # raise the debugger if present
                        ccall(:jl_raise_debugger, Int, ())
                    catch
                    end
                    line = ""
                    interrupted = true
                    break
                elseif isa(e,EOFError)
                    hit_eof = true
                    break
                else
                    rethrow()
                end
            end
            ast = Base.parse_input_line(line)
            (isa(ast,Expr) && ast.head === :incomplete) || break
        end
        if !isempty(line)
            response = eval_with_backend(ast, backend)
            print_response(repl, response, !ends_with_semicolon(line), false)
        end
        write(repl.terminal, '\n')
        ((!interrupted && isempty(line)) || hit_eof) && break
    end
    # terminate backend
    put!(backend.repl_channel, (nothing, -1))
    dopushdisplay && popdisplay(d)
    nothing
end

## LineEditREPL ##

mutable struct LineEditREPL <: AbstractREPL
    t::TextTerminal
    hascolor::Bool
    prompt_color::String
    input_color::String
    answer_color::String
    shell_color::String
    help_color::String
    history_file::Bool
    in_shell::Bool
    in_help::Bool
    envcolors::Bool
    waserror::Bool
    specialdisplay::Union{Nothing,AbstractDisplay}
    options::Options
    mistate::Union{MIState,Nothing}
    last_shown_line_infos::Vector{Tuple{String,Int}}
    interface::ModalInterface
    backendref::REPLBackendRef
    frontend_task::Task
    function LineEditREPL(t,hascolor,prompt_color,input_color,answer_color,shell_color,help_color,history_file,in_shell,in_help,envcolors)
        opts = Options()
        opts.hascolor = hascolor
        if !hascolor
            opts.beep_colors = [""]
        end
        new(t,hascolor,prompt_color,input_color,answer_color,shell_color,help_color,history_file,in_shell,
            in_help,envcolors,false,nothing, opts, nothing, Tuple{String,Int}[])
    end
end
outstream(r::LineEditREPL) = (t = r.t; t isa TTYTerminal ? t.out_stream : t)
specialdisplay(r::LineEditREPL) = r.specialdisplay
specialdisplay(r::AbstractREPL) = nothing
terminal(r::LineEditREPL) = r.t
hascolor(r::LineEditREPL) = r.hascolor

LineEditREPL(t::TextTerminal, hascolor::Bool, envcolors::Bool=false) =
    LineEditREPL(t, hascolor,
        hascolor ? Base.text_colors[:green] : "",
        hascolor ? Base.input_color() : "",
        hascolor ? Base.answer_color() : "",
        hascolor ? Base.text_colors[:red] : "",
        hascolor ? Base.text_colors[:yellow] : "",
        false, false, false, envcolors
    )

mutable struct REPLCompletionProvider <: CompletionProvider
    modifiers::LineEdit.Modifiers
end
REPLCompletionProvider() = REPLCompletionProvider(LineEdit.Modifiers())

mutable struct ShellCompletionProvider <: CompletionProvider end
struct LatexCompletions <: CompletionProvider end

function active_module() # this method is also called from Base
    isdefined(Base, :active_repl) || return Main
    return active_module(Base.active_repl::AbstractREPL)
end
active_module((; mistate)::LineEditREPL) = mistate === nothing ? Main : mistate.active_module
active_module(::AbstractREPL) = Main
active_module(d::REPLDisplay) = active_module(d.repl)

setmodifiers!(c::CompletionProvider, m::LineEdit.Modifiers) = nothing

setmodifiers!(c::REPLCompletionProvider, m::LineEdit.Modifiers) = c.modifiers = m

"""
    activate(mod::Module=Main)

Set `mod` as the default contextual module in the REPL,
both for evaluating expressions and printing them.
"""
function activate(mod::Module=Main)
    mistate = (Base.active_repl::LineEditREPL).mistate
    mistate === nothing && return nothing
    mistate.active_module = mod
    Base.load_InteractiveUtils(mod)
    return nothing
end

beforecursor(buf::IOBuffer) = String(buf.data[1:buf.ptr-1])

function complete_line(c::REPLCompletionProvider, s::PromptState, mod::Module)
    partial = beforecursor(s.input_buffer)
    full = LineEdit.input_string(s)
    ret, range, should_complete = completions(full, lastindex(partial), mod, c.modifiers.shift)
    c.modifiers = LineEdit.Modifiers()
    return unique!(map(completion_text, ret)), partial[range], should_complete
end

function complete_line(c::ShellCompletionProvider, s::PromptState)
    # First parse everything up to the current position
    partial = beforecursor(s.input_buffer)
    full = LineEdit.input_string(s)
    ret, range, should_complete = shell_completions(full, lastindex(partial))
    return unique!(map(completion_text, ret)), partial[range], should_complete
end

function complete_line(c::LatexCompletions, s)
    partial = beforecursor(LineEdit.buffer(s))
    full = LineEdit.input_string(s)::String
    ret, range, should_complete = bslash_completions(full, lastindex(partial))[2]
    return unique!(map(completion_text, ret)), partial[range], should_complete
end

with_repl_linfo(f, repl) = f(outstream(repl))
function with_repl_linfo(f, repl::LineEditREPL)
    linfos = Tuple{String,Int}[]
    io = IOContext(outstream(repl), :last_shown_line_infos => linfos)
    f(io)
    if !isempty(linfos)
        repl.last_shown_line_infos = linfos
    end
    nothing
end

mutable struct REPLHistoryProvider <: HistoryProvider
    history::Vector{String}
    file_path::String
    history_file::Union{Nothing,IO}
    start_idx::Int
    cur_idx::Int
    last_idx::Int
    last_buffer::IOBuffer
    last_mode::Union{Nothing,Prompt}
    mode_mapping::Dict{Symbol,Prompt}
    modes::Vector{Symbol}
end
REPLHistoryProvider(mode_mapping::Dict{Symbol}) =
    REPLHistoryProvider(String[], "", nothing, 0, 0, -1, IOBuffer(),
                        nothing, mode_mapping, UInt8[])

invalid_history_message(path::String) = """
Invalid history file ($path) format:
If you have a history file left over from an older version of Julia,
try renaming or deleting it.
Invalid character: """

munged_history_message(path::String) = """
Invalid history file ($path) format:
An editor may have converted tabs to spaces at line """

function hist_open_file(hp::REPLHistoryProvider)
    f = open(hp.file_path, read=true, write=true, create=true)
    hp.history_file = f
    seekend(f)
end

function hist_from_file(hp::REPLHistoryProvider, path::String)
    getline(lines, i) = i > length(lines) ? "" : lines[i]
    file_lines = readlines(path)
    countlines = 0
    while true
        # First parse the metadata that starts with '#' in particular the REPL mode
        countlines += 1
        line = getline(file_lines, countlines)
        mode = :julia
        isempty(line) && break
        line[1] != '#' &&
            error(invalid_history_message(path), repr(line[1]), " at line ", countlines)
        while !isempty(line)
            startswith(line, '#') || break
            if startswith(line, "# mode: ")
                mode = Symbol(SubString(line, 9))
            end
            countlines += 1
            line = getline(file_lines, countlines)
        end
        isempty(line) && break

        # Now parse the code for the current REPL mode
        line[1] == ' '  &&
            error(munged_history_message(path), countlines)
        line[1] != '\t' &&
            error(invalid_history_message(path), repr(line[1]), " at line ", countlines)
        lines = String[]
        while !isempty(line)
            push!(lines, chomp(SubString(line, 2)))
            next_line = getline(file_lines, countlines+1)
            isempty(next_line) && break
            first(next_line) == ' '  && error(munged_history_message(path), countlines)
            # A line not starting with a tab means we are done with code for this entry
            first(next_line) != '\t' && break
            countlines += 1
            line = getline(file_lines, countlines)
        end
        push!(hp.modes, mode)
        push!(hp.history, join(lines, '\n'))
    end
    hp.start_idx = length(hp.history)
    return hp
end

function add_history(hist::REPLHistoryProvider, s::PromptState)
    str = rstrip(String(take!(copy(s.input_buffer))))
    isempty(strip(str)) && return
    mode = mode_idx(hist, LineEdit.mode(s))
    !isempty(hist.history) &&
        isequal(mode, hist.modes[end]) && str == hist.history[end] && return
    push!(hist.modes, mode)
    push!(hist.history, str)
    hist.history_file === nothing && return
    entry = """
    # time: $(Libc.strftime("%Y-%m-%d %H:%M:%S %Z", time()))
    # mode: $mode
    $(replace(str, r"^"ms => "\t"))
    """
    # TODO: write-lock history file
    try
        seekend(hist.history_file)
    catch err
        (err isa SystemError) || rethrow()
        # File handle might get stale after a while, especially under network file systems
        # If this doesn't fix it (e.g. when file is deleted), we'll end up rethrowing anyway
        hist_open_file(hist)
    end
    print(hist.history_file, entry)
    flush(hist.history_file)
    nothing
end

function history_move(s::Union{LineEdit.MIState,LineEdit.PrefixSearchState}, hist::REPLHistoryProvider, idx::Int, save_idx::Int = hist.cur_idx)
    max_idx = length(hist.history) + 1
    @assert 1 <= hist.cur_idx <= max_idx
    (1 <= idx <= max_idx) || return :none
    idx != hist.cur_idx || return :none

    # save the current line
    if save_idx == max_idx
        hist.last_mode = LineEdit.mode(s)
        hist.last_buffer = copy(LineEdit.buffer(s))
    else
        hist.history[save_idx] = LineEdit.input_string(s)
        hist.modes[save_idx] = mode_idx(hist, LineEdit.mode(s))
    end

    # load the saved line
    if idx == max_idx
        last_buffer = hist.last_buffer
        LineEdit.transition(s, hist.last_mode) do
            LineEdit.replace_line(s, last_buffer)
        end
        hist.last_mode = nothing
        hist.last_buffer = IOBuffer()
    else
        if haskey(hist.mode_mapping, hist.modes[idx])
            LineEdit.transition(s, hist.mode_mapping[hist.modes[idx]]) do
                LineEdit.replace_line(s, hist.history[idx])
            end
        else
            return :skip
        end
    end
    hist.cur_idx = idx

    return :ok
end

# REPL History can also transitions modes
function LineEdit.accept_result_newmode(hist::REPLHistoryProvider)
    if 1 <= hist.cur_idx <= length(hist.modes)
        return hist.mode_mapping[hist.modes[hist.cur_idx]]
    end
    return nothing
end

function history_prev(s::LineEdit.MIState, hist::REPLHistoryProvider,
                      num::Int=1, save_idx::Int = hist.cur_idx)
    num <= 0 && return history_next(s, hist, -num, save_idx)
    hist.last_idx = -1
    m = history_move(s, hist, hist.cur_idx-num, save_idx)
    if m === :ok
        LineEdit.move_input_start(s)
        LineEdit.reset_key_repeats(s) do
            LineEdit.move_line_end(s)
        end
        return LineEdit.refresh_line(s)
    elseif m === :skip
        return history_prev(s, hist, num+1, save_idx)
    else
        return Terminals.beep(s)
    end
end

function history_next(s::LineEdit.MIState, hist::REPLHistoryProvider,
                      num::Int=1, save_idx::Int = hist.cur_idx)
    if num == 0
        Terminals.beep(s)
        return
    end
    num < 0 && return history_prev(s, hist, -num, save_idx)
    cur_idx = hist.cur_idx
    max_idx = length(hist.history) + 1
    if cur_idx == max_idx && 0 < hist.last_idx
        # issue #6312
        cur_idx = hist.last_idx
        hist.last_idx = -1
    end
    m = history_move(s, hist, cur_idx+num, save_idx)
    if m === :ok
        LineEdit.move_input_end(s)
        return LineEdit.refresh_line(s)
    elseif m === :skip
        return history_next(s, hist, num+1, save_idx)
    else
        return Terminals.beep(s)
    end
end

history_first(s::LineEdit.MIState, hist::REPLHistoryProvider) =
    history_prev(s, hist, hist.cur_idx - 1 -
                 (hist.cur_idx > hist.start_idx+1 ? hist.start_idx : 0))

history_last(s::LineEdit.MIState, hist::REPLHistoryProvider) =
    history_next(s, hist, length(hist.history) - hist.cur_idx + 1)

function history_move_prefix(s::LineEdit.PrefixSearchState,
                             hist::REPLHistoryProvider,
                             prefix::AbstractString,
                             backwards::Bool,
                             cur_idx::Int = hist.cur_idx)
    cur_response = String(take!(copy(LineEdit.buffer(s))))
    # when searching forward, start at last_idx
    if !backwards && hist.last_idx > 0
        cur_idx = hist.last_idx
    end
    hist.last_idx = -1
    max_idx = length(hist.history)+1
    idxs = backwards ? ((cur_idx-1):-1:1) : ((cur_idx+1):1:max_idx)
    for idx in idxs
        if (idx == max_idx) || (startswith(hist.history[idx], prefix) && (hist.history[idx] != cur_response || get(hist.mode_mapping, hist.modes[idx], nothing) !== LineEdit.mode(s)))
            m = history_move(s, hist, idx)
            if m === :ok
                if idx == max_idx
                    # on resuming the in-progress edit, leave the cursor where the user last had it
                elseif isempty(prefix)
                    # on empty prefix search, move cursor to the end
                    LineEdit.move_input_end(s)
                else
                    # otherwise, keep cursor at the prefix position as a visual cue
                    seek(LineEdit.buffer(s), sizeof(prefix))
                end
                LineEdit.refresh_line(s)
                return :ok
            elseif m === :skip
                return history_move_prefix(s,hist,prefix,backwards,idx)
            end
        end
    end
    Terminals.beep(s)
    nothing
end
history_next_prefix(s::LineEdit.PrefixSearchState, hist::REPLHistoryProvider, prefix::AbstractString) =
    history_move_prefix(s, hist, prefix, false)
history_prev_prefix(s::LineEdit.PrefixSearchState, hist::REPLHistoryProvider, prefix::AbstractString) =
    history_move_prefix(s, hist, prefix, true)

function history_search(hist::REPLHistoryProvider, query_buffer::IOBuffer, response_buffer::IOBuffer,
                        backwards::Bool=false, skip_current::Bool=false)

    qpos = position(query_buffer)
    qpos > 0 || return true
    searchdata = beforecursor(query_buffer)
    response_str = String(take!(copy(response_buffer)))

    # Alright, first try to see if the current match still works
    a = position(response_buffer) + 1 # position is zero-indexed
    # FIXME: I'm pretty sure this is broken since it uses an index
    # into the search data to index into the response string
    b = a + sizeof(searchdata)
    b = b ≤ ncodeunits(response_str) ? prevind(response_str, b) : b-1
    b = min(lastindex(response_str), b) # ensure that b is valid

    searchstart = backwards ? b : a
    if searchdata == response_str[a:b]
        if skip_current
            searchstart = backwards ? prevind(response_str, b) : nextind(response_str, a)
        else
            return true
        end
    end

    # Start searching
    # First the current response buffer
    if 1 <= searchstart <= lastindex(response_str)
        match = backwards ? findprev(searchdata, response_str, searchstart) :
                            findnext(searchdata, response_str, searchstart)
        if match !== nothing
            seek(response_buffer, first(match) - 1)
            return true
        end
    end

    # Now search all the other buffers
    idxs = backwards ? ((hist.cur_idx-1):-1:1) : ((hist.cur_idx+1):1:length(hist.history))
    for idx in idxs
        h = hist.history[idx]
        match = backwards ? findlast(searchdata, h) : findfirst(searchdata, h)
        if match !== nothing && h != response_str && haskey(hist.mode_mapping, hist.modes[idx])
            truncate(response_buffer, 0)
            write(response_buffer, h)
            seek(response_buffer, first(match) - 1)
            hist.cur_idx = idx
            return true
        end
    end

    return false
end

function history_reset_state(hist::REPLHistoryProvider)
    if hist.cur_idx != length(hist.history) + 1
        hist.last_idx = hist.cur_idx
        hist.cur_idx = length(hist.history) + 1
    end
    nothing
end
LineEdit.reset_state(hist::REPLHistoryProvider) = history_reset_state(hist)

function return_callback(s)
    ast = Base.parse_input_line(String(take!(copy(LineEdit.buffer(s)))), depwarn=false)
    return !(isa(ast, Expr) && ast.head === :incomplete)
end

find_hist_file() = get(ENV, "JULIA_HISTORY",
                       !isempty(DEPOT_PATH) ? joinpath(DEPOT_PATH[1], "logs", "repl_history.jl") :
                       error("DEPOT_PATH is empty and ENV[\"JULIA_HISTORY\"] not set."))

backend(r::AbstractREPL) = r.backendref

function eval_with_backend(ast, backend::REPLBackendRef)
    put!(backend.repl_channel, (ast, 1))
    return take!(backend.response_channel) # (val, iserr)
end

function respond(f, repl, main; pass_empty::Bool = false, suppress_on_semicolon::Bool = true)
    return function do_respond(s::MIState, buf, ok::Bool)
        if !ok
            return transition(s, :abort)
        end
        line = String(take!(buf)::Vector{UInt8})
        if !isempty(line) || pass_empty
            reset(repl)
            local response
            try
                ast = Base.invokelatest(f, line)
                response = eval_with_backend(ast, backend(repl))
            catch
                response = Pair{Any, Bool}(current_exceptions(), true)
            end
            hide_output = suppress_on_semicolon && ends_with_semicolon(line)
            print_response(repl, response, !hide_output, hascolor(repl))
        end
        prepare_next(repl)
        reset_state(s)
        return s.current_mode.sticky ? true : transition(s, main)
    end
end

function reset(repl::LineEditREPL)
    raw!(repl.t, false)
    hascolor(repl) && print(repl.t, Base.text_colors[:normal])
    nothing
end

function prepare_next(repl::LineEditREPL)
    println(terminal(repl))
end

function mode_keymap(julia_prompt::Prompt)
    AnyDict(
    '\b' => function (s::MIState,o...)
        if isempty(s) || position(LineEdit.buffer(s)) == 0
            buf = copy(LineEdit.buffer(s))
            transition(s, julia_prompt) do
                LineEdit.state(s, julia_prompt).input_buffer = buf
            end
        else
            LineEdit.edit_backspace(s)
        end
    end,
    "^C" => function (s::MIState,o...)
        LineEdit.move_input_end(s)
        LineEdit.refresh_line(s)
        print(LineEdit.terminal(s), "^C\n\n")
        transition(s, julia_prompt)
        transition(s, :reset)
        LineEdit.refresh_line(s)
    end)
end

repl_filename(repl, hp::REPLHistoryProvider) = "REPL[$(max(length(hp.history)-hp.start_idx, 1))]"
repl_filename(repl, hp) = "REPL"

const JL_PROMPT_PASTE = Ref(true)
enable_promptpaste(v::Bool) = JL_PROMPT_PASTE[] = v

function contextual_prompt(repl::LineEditREPL, prompt::Union{String,Function})
    function ()
        mod = active_module(repl)
        prefix = mod == Main ? "" : string('(', mod, ") ")
        pr = prompt isa String ? prompt : prompt()
        prefix * pr
    end
end

setup_interface(
    repl::LineEditREPL;
    # those keyword arguments may be deprecated eventually in favor of the Options mechanism
    hascolor::Bool = repl.options.hascolor,
    extra_repl_keymap::Any = repl.options.extra_keymap
) = setup_interface(repl, hascolor, extra_repl_keymap)

# This non keyword method can be precompiled which is important
function setup_interface(
    repl::LineEditREPL,
    hascolor::Bool,
    extra_repl_keymap::Any, # Union{Dict,Vector{<:Dict}},
)
    # The precompile statement emitter has problem outputting valid syntax for the
    # type of `Union{Dict,Vector{<:Dict}}` (see #28808).
    # This function is however important to precompile for REPL startup time, therefore,
    # make the type Any and just assert that we have the correct type below.
    @assert extra_repl_keymap isa Union{Dict,Vector{<:Dict}}

    ###
    #
    # This function returns the main interface that describes the REPL
    # functionality, it is called internally by functions that setup a
    # Terminal-based REPL frontend.
    #
    # See run_frontend(repl::LineEditREPL, backend::REPLBackendRef)
    # for usage
    #
    ###

    ###
    # We setup the interface in two stages.
    # First, we set up all components (prompt,rsearch,shell,help)
    # Second, we create keymaps with appropriate transitions between them
    #   and assign them to the components
    #
    ###

    ############################### Stage I ################################

    # This will provide completions for REPL and help mode
    replc = REPLCompletionProvider()

    # Set up the main Julia prompt
    julia_prompt = Prompt(contextual_prompt(repl, JULIA_PROMPT);
        # Copy colors from the prompt object
        prompt_prefix = hascolor ? repl.prompt_color : "",
        prompt_suffix = hascolor ?
            (repl.envcolors ? Base.input_color : repl.input_color) : "",
        repl = repl,
        complete = replc,
        on_enter = return_callback)

    # Setup help mode
    help_mode = Prompt(contextual_prompt(repl, "help?> "),
        prompt_prefix = hascolor ? repl.help_color : "",
        prompt_suffix = hascolor ?
            (repl.envcolors ? Base.input_color : repl.input_color) : "",
        repl = repl,
        complete = replc,
        # When we're done transform the entered line into a call to helpmode function
        on_done = respond(line::String->helpmode(outstream(repl), line, repl.mistate.active_module),
                          repl, julia_prompt, pass_empty=true, suppress_on_semicolon=false))


    # Set up shell mode
    shell_mode = Prompt(SHELL_PROMPT;
        prompt_prefix = hascolor ? repl.shell_color : "",
        prompt_suffix = hascolor ?
            (repl.envcolors ? Base.input_color : repl.input_color) : "",
        repl = repl,
        complete = ShellCompletionProvider(),
        # Transform "foo bar baz" into `foo bar baz` (shell quoting)
        # and pass into Base.repl_cmd for processing (handles `ls` and `cd`
        # special)
        on_done = respond(repl, julia_prompt) do line
            Expr(:call, :(Base.repl_cmd),
                :(Base.cmd_gen($(Base.shell_parse(line::String)[1]))),
                outstream(repl))
        end,
        sticky = true)


    ################################# Stage II #############################

    # Setup history
    # We will have a unified history for all REPL modes
    hp = REPLHistoryProvider(Dict{Symbol,Prompt}(:julia => julia_prompt,
                                                 :shell => shell_mode,
                                                 :help  => help_mode))
    if repl.history_file
        try
            hist_path = find_hist_file()
            mkpath(dirname(hist_path))
            hp.file_path = hist_path
            hist_open_file(hp)
            finalizer(replc) do replc
                close(hp.history_file)
            end
            hist_from_file(hp, hist_path)
        catch
            # use REPL.hascolor to avoid using the local variable with the same name
            print_response(repl, Pair{Any, Bool}(current_exceptions(), true), true, REPL.hascolor(repl))
            println(outstream(repl))
            @info "Disabling history file for this session"
            repl.history_file = false
        end
    end
    history_reset_state(hp)
    julia_prompt.hist = hp
    shell_mode.hist = hp
    help_mode.hist = hp

    julia_prompt.on_done = respond(x->Base.parse_input_line(x,filename=repl_filename(repl,hp)), repl, julia_prompt)


    search_prompt, skeymap = LineEdit.setup_search_keymap(hp)
    search_prompt.complete = LatexCompletions()

    shell_prompt_len = length(SHELL_PROMPT)
    help_prompt_len = length(HELP_PROMPT)
    jl_prompt_regex = r"^In \[[0-9]+\]: |^(?:\(.+\) )?julia> "
    pkg_prompt_regex = r"^(?:\(.+\) )?pkg> "

    # Canonicalize user keymap input
    if isa(extra_repl_keymap, Dict)
        extra_repl_keymap = AnyDict[extra_repl_keymap]
    end

    repl_keymap = AnyDict(
        ';' => function (s::MIState,o...)
            if isempty(s) || position(LineEdit.buffer(s)) == 0
                buf = copy(LineEdit.buffer(s))
                transition(s, shell_mode) do
                    LineEdit.state(s, shell_mode).input_buffer = buf
                end
            else
                edit_insert(s, ';')
            end
        end,
        '?' => function (s::MIState,o...)
            if isempty(s) || position(LineEdit.buffer(s)) == 0
                buf = copy(LineEdit.buffer(s))
                transition(s, help_mode) do
                    LineEdit.state(s, help_mode).input_buffer = buf
                end
            else
                edit_insert(s, '?')
            end
        end,
        ']' => function (s::MIState,o...)
            if isempty(s) || position(LineEdit.buffer(s)) == 0
                pkgid = Base.PkgId(Base.UUID("44cfe95a-1eb2-52ea-b672-e2afdf69b78f"), "Pkg")
                REPLExt = Base.require_stdlib(pkgid, "REPLExt")
                pkg_mode = nothing
                if REPLExt isa Module && isdefined(REPLExt, :PkgCompletionProvider)
                    for mode in repl.interface.modes
                        if mode isa LineEdit.Prompt && mode.complete isa REPLExt.PkgCompletionProvider
                            pkg_mode = mode
                            break
                        end
                    end
                end
                # TODO: Cache the `pkg_mode`?
                if pkg_mode !== nothing
                    buf = copy(LineEdit.buffer(s))
                    transition(s, pkg_mode) do
                        LineEdit.state(s, pkg_mode).input_buffer = buf
                    end
                    return
                end
            end
            edit_insert(s, ']')
        end,

        # Bracketed Paste Mode
        "\e[200~" => (s::MIState,o...)->begin
            input = LineEdit.bracketed_paste(s) # read directly from s until reaching the end-bracketed-paste marker
            sbuffer = LineEdit.buffer(s)
            curspos = position(sbuffer)
            seek(sbuffer, 0)
            shouldeval = (bytesavailable(sbuffer) == curspos && !occursin(UInt8('\n'), sbuffer))
            seek(sbuffer, curspos)
            if curspos == 0
                # if pasting at the beginning, strip leading whitespace
                input = lstrip(input)
            end
            if !shouldeval
                # when pasting in the middle of input, just paste in place
                # don't try to execute all the WIP, since that's rather confusing
                # and is often ill-defined how it should behave
                edit_insert(s, input)
                return
            end
            LineEdit.push_undo(s)
            edit_insert(sbuffer, input)
            input = String(take!(sbuffer))
            oldpos = firstindex(input)
            firstline = true
            isprompt_paste = false
            curr_prompt_len = 0
            pasting_help = false

            while oldpos <= lastindex(input) # loop until all lines have been executed
                if JL_PROMPT_PASTE[]
                    # Check if the next statement starts with a prompt i.e. "julia> ", in that case
                    # skip it. But first skip whitespace unless pasting in a docstring which may have
                    # indented prompt examples that we don't want to execute
                    while input[oldpos] in (pasting_help ? ('\n') : ('\n', ' ', '\t'))
                        oldpos = nextind(input, oldpos)
                        oldpos >= sizeof(input) && return
                    end
                    substr = SubString(input, oldpos)
                    # Check if input line starts with "julia> ", remove it if we are in prompt paste mode
                    if (firstline || isprompt_paste) && startswith(substr, jl_prompt_regex)
                        detected_jl_prompt = match(jl_prompt_regex, substr).match
                        isprompt_paste = true
                        curr_prompt_len = sizeof(detected_jl_prompt)
                        oldpos += curr_prompt_len
                        transition(s, julia_prompt)
                        pasting_help = false
                    # Check if input line starts with "pkg> " or "(...) pkg> ", remove it if we are in prompt paste mode and switch mode
                    elseif (firstline || isprompt_paste) && startswith(substr, pkg_prompt_regex)
                        detected_pkg_prompt = match(pkg_prompt_regex, substr).match
                        isprompt_paste = true
                        curr_prompt_len = sizeof(detected_pkg_prompt)
                        oldpos += curr_prompt_len
                        Base.active_repl.interface.modes[1].keymap_dict[']'](s, o...)
                        pasting_help = false
                    # Check if input line starts with "shell> ", remove it if we are in prompt paste mode and switch mode
                    elseif (firstline || isprompt_paste) && startswith(substr, SHELL_PROMPT)
                        isprompt_paste = true
                        oldpos += shell_prompt_len
                        curr_prompt_len = shell_prompt_len
                        transition(s, shell_mode)
                        pasting_help = false
                    # Check if input line starts with "help?> ", remove it if we are in prompt paste mode and switch mode
                    elseif (firstline || isprompt_paste) && startswith(substr, HELP_PROMPT)
                        isprompt_paste = true
                        oldpos += help_prompt_len
                        curr_prompt_len = help_prompt_len
                        transition(s, help_mode)
                        pasting_help = true
                    # If we are prompt pasting and current statement does not begin with a mode prefix, skip to next line
                    elseif isprompt_paste
                        while input[oldpos] != '\n'
                            oldpos = nextind(input, oldpos)
                            oldpos >= sizeof(input) && return
                        end
                        continue
                    end
                end
                dump_tail = false
                nl_pos = findfirst('\n', input[oldpos:end])
                if s.current_mode == julia_prompt
                    ast, pos = Meta.parse(input, oldpos, raise=false, depwarn=false)
                    if (isa(ast, Expr) && (ast.head === :error || ast.head === :incomplete)) ||
                            (pos > ncodeunits(input) && !endswith(input, '\n'))
                        # remaining text is incomplete (an error, or parser ran to the end but didn't stop with a newline):
                        # Insert all the remaining text as one line (might be empty)
                        dump_tail = true
                    end
                elseif isnothing(nl_pos) # no newline at end, so just dump the tail into the prompt and don't execute
                    dump_tail = true
                elseif s.current_mode == shell_mode # handle multiline shell commands
                    lines = split(input[oldpos:end], '\n')
                    pos = oldpos + sizeof(lines[1]) + 1
                    if length(lines) > 1
                        for line in lines[2:end]
                            # to be recognized as a multiline shell command, the lines must be indented to the
                            # same prompt position
                            if !startswith(line, ' '^curr_prompt_len)
                                break
                            end
                            pos += sizeof(line) + 1
                        end
                    end
                else
                    pos = oldpos + nl_pos
                end
                if dump_tail
                    tail = input[oldpos:end]
                    if !firstline
                        # strip leading whitespace, but only if it was the result of executing something
                        # (avoids modifying the user's current leading wip line)
                        tail = lstrip(tail)
                    end
                    if isprompt_paste # remove indentation spaces corresponding to the prompt
                        tail = replace(tail, r"^"m * ' '^curr_prompt_len => "")
                    end
                    LineEdit.replace_line(s, tail, true)
                    LineEdit.refresh_line(s)
                    break
                end
                # get the line and strip leading and trailing whitespace
                line = strip(input[oldpos:prevind(input, pos)])
                if !isempty(line)
                    if isprompt_paste # remove indentation spaces corresponding to the prompt
                        line = replace(line, r"^"m * ' '^curr_prompt_len => "")
                    end
                    # put the line on the screen and history
                    LineEdit.replace_line(s, line)
                    LineEdit.commit_line(s)
                    # execute the statement
                    terminal = LineEdit.terminal(s) # This is slightly ugly but ok for now
                    raw!(terminal, false) && disable_bracketed_paste(terminal)
                    @invokelatest LineEdit.mode(s).on_done(s, LineEdit.buffer(s), true)
                    raw!(terminal, true) && enable_bracketed_paste(terminal)
                    LineEdit.push_undo(s) # when the last line is incomplete
                end
                oldpos = pos
                firstline = false
            end
        end,

        # Open the editor at the location of a stackframe or method
        # This is accessing a contextual variable that gets set in
        # the show_backtrace and show_method_table functions.
        "^Q" => (s::MIState, o...) -> begin
            linfos = repl.last_shown_line_infos
            str = String(take!(LineEdit.buffer(s)))
            n = tryparse(Int, str)
            n === nothing && @goto writeback
            if n <= 0 || n > length(linfos) || startswith(linfos[n][1], "REPL[")
                @goto writeback
            end
            try
                InteractiveUtils.edit(Base.fixup_stdlib_path(linfos[n][1]), linfos[n][2])
            catch ex
                ex isa ProcessFailedException || ex isa Base.IOError || ex isa SystemError || rethrow()
                @info "edit failed" _exception=ex
            end
            LineEdit.refresh_line(s)
            return
            @label writeback
            write(LineEdit.buffer(s), str)
            return
        end,
    )

    prefix_prompt, prefix_keymap = LineEdit.setup_prefix_keymap(hp, julia_prompt)

    a = Dict{Any,Any}[skeymap, repl_keymap, prefix_keymap, LineEdit.history_keymap, LineEdit.default_keymap, LineEdit.escape_defaults]
    prepend!(a, extra_repl_keymap)

    julia_prompt.keymap_dict = LineEdit.keymap(a)

    mk = mode_keymap(julia_prompt)

    b = Dict{Any,Any}[skeymap, mk, prefix_keymap, LineEdit.history_keymap, LineEdit.default_keymap, LineEdit.escape_defaults]
    prepend!(b, extra_repl_keymap)

    shell_mode.keymap_dict = help_mode.keymap_dict = LineEdit.keymap(b)

    allprompts = LineEdit.TextInterface[julia_prompt, shell_mode, help_mode, search_prompt, prefix_prompt]
    return ModalInterface(allprompts)
end

function run_frontend(repl::LineEditREPL, backend::REPLBackendRef)
    repl.frontend_task = current_task()
    d = REPLDisplay(repl)
    dopushdisplay = repl.specialdisplay === nothing && !in(d,Base.Multimedia.displays)
    dopushdisplay && pushdisplay(d)
    if !isdefined(repl,:interface)
        interface = repl.interface = setup_interface(repl)
    else
        interface = repl.interface
    end
    repl.backendref = backend
    repl.mistate = LineEdit.init_state(terminal(repl), interface)
    run_interface(terminal(repl), interface, repl.mistate)
    # Terminate Backend
    put!(backend.repl_channel, (nothing, -1))
    dopushdisplay && popdisplay(d)
    nothing
end

## StreamREPL ##

mutable struct StreamREPL <: AbstractREPL
    stream::IO
    prompt_color::String
    input_color::String
    answer_color::String
    waserror::Bool
    frontend_task::Task
    StreamREPL(stream,pc,ic,ac) = new(stream,pc,ic,ac,false)
end
StreamREPL(stream::IO) = StreamREPL(stream, Base.text_colors[:green], Base.input_color(), Base.answer_color())
run_repl(stream::IO) = run_repl(StreamREPL(stream))

outstream(s::StreamREPL) = s.stream
hascolor(s::StreamREPL) = get(s.stream, :color, false)::Bool

answer_color(r::LineEditREPL) = r.envcolors ? Base.answer_color() : r.answer_color
answer_color(r::StreamREPL) = r.answer_color
input_color(r::LineEditREPL) = r.envcolors ? Base.input_color() : r.input_color
input_color(r::StreamREPL) = r.input_color

let matchend = Dict("\"" => r"\"", "\"\"\"" => r"\"\"\"", "'" => r"'",
    "`" => r"`", "```" => r"```", "#" => r"$"m, "#=" => r"=#|#=")
    global _rm_strings_and_comments
    function _rm_strings_and_comments(code::Union{String,SubString{String}})
        buf = IOBuffer(sizehint = sizeof(code))
        pos = 1
        while true
            i = findnext(r"\"(?!\"\")|\"\"\"|'|`(?!``)|```|#(?!=)|#=", code, pos)
            isnothing(i) && break
            match = SubString(code, i)
            j = findnext(matchend[match]::Regex, code, nextind(code, last(i)))
            if match == "#=" # possibly nested
                nested = 1
                while j !== nothing
                    nested += SubString(code, j) == "#=" ? +1 : -1
                    iszero(nested) && break
                    j = findnext(r"=#|#=", code, nextind(code, last(j)))
                end
            elseif match[1] != '#' # quote match: check non-escaped
                while j !== nothing
                    notbackslash = findprev(!=('\\'), code, prevind(code, first(j)))::Int
                    isodd(first(j) - notbackslash) && break # not escaped
                    j = findnext(matchend[match]::Regex, code, nextind(code, first(j)))
                end
            end
            isnothing(j) && break
            if match[1] == '#'
                print(buf, SubString(code, pos, prevind(code, first(i))))
            else
                print(buf, SubString(code, pos, last(i)), ' ', SubString(code, j))
            end
            pos = nextind(code, last(j))
        end
        print(buf, SubString(code, pos, lastindex(code)))
        return String(take!(buf))
    end
end

# heuristic function to decide if the presence of a semicolon
# at the end of the expression was intended for suppressing output
ends_with_semicolon(code::AbstractString) = ends_with_semicolon(String(code))
ends_with_semicolon(code::Union{String,SubString{String}}) =
    contains(_rm_strings_and_comments(code), r";\s*$")

function banner(io::IO = stdout; short = false)
    if Base.GIT_VERSION_INFO.tagged_commit
        commit_string = Base.TAGGED_RELEASE_BANNER
    elseif isempty(Base.GIT_VERSION_INFO.commit)
        commit_string = ""
    else
        days = Int(floor((ccall(:jl_clock_now, Float64, ()) - Base.GIT_VERSION_INFO.fork_master_timestamp) / (60 * 60 * 24)))
        days = max(0, days)
        unit = days == 1 ? "day" : "days"
        distance = Base.GIT_VERSION_INFO.fork_master_distance
        commit = Base.GIT_VERSION_INFO.commit_short

        if distance == 0
            commit_string = "Commit $(commit) ($(days) $(unit) old master)"
        else
            branch = Base.GIT_VERSION_INFO.branch
            commit_string = "$(branch)/$(commit) (fork: $(distance) commits, $(days) $(unit))"
        end
    end

    commit_date = isempty(Base.GIT_VERSION_INFO.date_string) ? "" : " ($(split(Base.GIT_VERSION_INFO.date_string)[1]))"

    if get(io, :color, false)::Bool
        c = Base.text_colors
        tx = c[:normal] # text
        jl = c[:normal] # julia
        d1 = c[:bold] * c[:blue]    # first dot
        d2 = c[:bold] * c[:red]     # second dot
        d3 = c[:bold] * c[:green]   # third dot
        d4 = c[:bold] * c[:magenta] # fourth dot

        if short
            print(io,"""
              $(d3)o$(tx)  | Version $(VERSION)$(commit_date)
             $(d2)o$(tx) $(d4)o$(tx) | $(commit_string)
            """)
        else
            print(io,"""               $(d3)_$(tx)
               $(d1)_$(tx)       $(jl)_$(tx) $(d2)_$(d3)(_)$(d4)_$(tx)     |  Documentation: https://docs.julialang.org
              $(d1)(_)$(jl)     | $(d2)(_)$(tx) $(d4)(_)$(tx)    |
               $(jl)_ _   _| |_  __ _$(tx)   |  Type \"?\" for help, \"]?\" for Pkg help.
              $(jl)| | | | | | |/ _` |$(tx)  |
              $(jl)| | |_| | | | (_| |$(tx)  |  Version $(VERSION)$(commit_date)
             $(jl)_/ |\\__'_|_|_|\\__'_|$(tx)  |  $(commit_string)
            $(jl)|__/$(tx)                   |

            """)
        end
    else
        if short
            print(io,"""
              o  |  Version $(VERSION)$(commit_date)
             o o |  $(commit_string)
            """)
        else
            print(io,"""
                           _
               _       _ _(_)_     |  Documentation: https://docs.julialang.org
              (_)     | (_) (_)    |
               _ _   _| |_  __ _   |  Type \"?\" for help, \"]?\" for Pkg help.
              | | | | | | |/ _` |  |
              | | |_| | | | (_| |  |  Version $(VERSION)$(commit_date)
             _/ |\\__'_|_|_|\\__'_|  |  $(commit_string)
            |__/                   |

            """)
        end
    end
end

function run_frontend(repl::StreamREPL, backend::REPLBackendRef)
    repl.frontend_task = current_task()
    have_color = hascolor(repl)
    banner(repl.stream)
    d = REPLDisplay(repl)
    dopushdisplay = !in(d,Base.Multimedia.displays)
    dopushdisplay && pushdisplay(d)
    while !eof(repl.stream)::Bool
        if have_color
            print(repl.stream,repl.prompt_color)
        end
        print(repl.stream, "julia> ")
        if have_color
            print(repl.stream, input_color(repl))
        end
        line = readline(repl.stream, keep=true)
        if !isempty(line)
            ast = Base.parse_input_line(line)
            if have_color
                print(repl.stream, Base.color_normal)
            end
            response = eval_with_backend(ast, backend)
            print_response(repl, response, !ends_with_semicolon(line), have_color)
        end
    end
    # Terminate Backend
    put!(backend.repl_channel, (nothing, -1))
    dopushdisplay && popdisplay(d)
    nothing
end

module Numbered

using ..REPL

__current_ast_transforms() = isdefined(Base, :active_repl_backend) ? Base.active_repl_backend.ast_transforms : REPL.repl_ast_transforms

function repl_eval_counter(hp)
    return length(hp.history) - hp.start_idx
end

function out_transform(@nospecialize(x), n::Ref{Int})
    return Expr(:toplevel, get_usings!([], x)..., quote
        let __temp_val_a72df459 = $x
            $capture_result($n, __temp_val_a72df459)
            __temp_val_a72df459
        end
    end)
end

function get_usings!(usings, ex)
    ex isa Expr || return usings
    # get all `using` and `import` statements which are at the top level
    for (i, arg) in enumerate(ex.args)
        if Base.isexpr(arg, :toplevel)
            get_usings!(usings, arg)
        elseif Base.isexpr(arg, [:using, :import])
            push!(usings, popat!(ex.args, i))
        end
    end
    return usings
end

function capture_result(n::Ref{Int}, @nospecialize(x))
    n = n[]
    mod = Base.MainInclude
    if !isdefined(mod, :Out)
        @eval mod global Out
        @eval mod export Out
        setglobal!(mod, :Out, Dict{Int, Any}())
    end
    if x !== getglobal(mod, :Out) && x !== nothing # remove this?
        getglobal(mod, :Out)[n] = x
    end
    nothing
end

function set_prompt(repl::LineEditREPL, n::Ref{Int})
    julia_prompt = repl.interface.modes[1]
    julia_prompt.prompt = function()
        n[] = repl_eval_counter(julia_prompt.hist)+1
        string("In [", n[], "]: ")
    end
    nothing
end

function set_output_prefix(repl::LineEditREPL, n::Ref{Int})
    julia_prompt = repl.interface.modes[1]
    if REPL.hascolor(repl)
        julia_prompt.output_prefix_prefix = Base.text_colors[:red]
    end
    julia_prompt.output_prefix = () -> string("Out[", n[], "]: ")
    nothing
end

function __current_ast_transforms(backend)
    if backend === nothing
        isdefined(Base, :active_repl_backend) ? Base.active_repl_backend.ast_transforms : REPL.repl_ast_transforms
    else
        backend.ast_transforms
    end
end

function numbered_prompt!(repl::LineEditREPL=Base.active_repl, backend=nothing)
    n = Ref{Int}(0)
    set_prompt(repl, n)
    set_output_prefix(repl, n)
    push!(__current_ast_transforms(backend), @nospecialize(ast) -> out_transform(ast, n))
    return
end

"""
    Out[n]

A variable referring to all previously computed values, automatically imported to the interactive prompt.
Only defined and exists while using [Numbered prompt](@ref Numbered-prompt).

See also [`ans`](@ref).
"""
Base.MainInclude.Out

end

import .Numbered.numbered_prompt!

# this assignment won't survive precompilation,
# but will stick if REPL is baked into a sysimg.
# Needs to occur after this module is finished.
Base.REPL_MODULE_REF[] = REPL

if Base.generating_output()
    include("precompile.jl")
end

end # module

JuliaLang / julia / #37745

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