18643242364

Committed 20 Oct 2025 05:37AM UTC coverage: 95.927% (-0.03%) from 95.956%

Build # 18643242364

Build Type

Pull #4800

github

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web-flow

Commit Message

Merge 3c59c8f0e into e97cf5bdb

Pull Request Pull Request #4800: fix_fmt_skip_in_one_liners

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97.73

/src/black/comments.py

import re
from collections.abc import Collection, Iterator
from dataclasses import dataclass
from functools import lru_cache
from typing import Final, Optional, Union

from black.mode import Mode, Preview
from black.nodes import (
    CLOSING_BRACKETS,
    STANDALONE_COMMENT,
    STATEMENT,
    WHITESPACE,
    container_of,
    first_leaf_of,
    is_type_comment_string,
    make_simple_prefix,
    preceding_leaf,
    syms,
)
from blib2to3.pgen2 import token
from blib2to3.pytree import Leaf, Node

# types
LN = Union[Leaf, Node]

FMT_OFF: Final = {"# fmt: off", "# fmt:off", "# yapf: disable"}
FMT_SKIP: Final = {"# fmt: skip", "# fmt:skip"}
FMT_ON: Final = {"# fmt: on", "# fmt:on", "# yapf: enable"}

# Compound statements we care about for fmt: skip handling
# (excludes except_clause and case_block which aren't standalone compound statements)
_COMPOUND_STATEMENTS: Final = STATEMENT - {syms.except_clause, syms.case_block}

COMMENT_EXCEPTIONS = " !:#'"
_COMMENT_PREFIX = "# "
_COMMENT_LIST_SEPARATOR = ";"


@dataclass
class ProtoComment:
    """Describes a piece of syntax that is a comment.

    It's not a :class:`blib2to3.pytree.Leaf` so that:

    * it can be cached (`Leaf` objects should not be reused more than once as
      they store their lineno, column, prefix, and parent information);
    * `newlines` and `consumed` fields are kept separate from the `value`. This
      simplifies handling of special marker comments like ``# fmt: off/on``.
    """

    type: int  # token.COMMENT or STANDALONE_COMMENT
    value: str  # content of the comment
    newlines: int  # how many newlines before the comment
    consumed: int  # how many characters of the original leaf's prefix did we consume
    form_feed: bool  # is there a form feed before the comment
    leading_whitespace: str  # leading whitespace before the comment, if any


def generate_comments(leaf: LN, mode: Mode) -> Iterator[Leaf]:
    """Clean the prefix of the `leaf` and generate comments from it, if any.

    Comments in lib2to3 are shoved into the whitespace prefix.  This happens
    in `pgen2/driver.py:Driver.parse_tokens()`.  This was a brilliant implementation
    move because it does away with modifying the grammar to include all the
    possible places in which comments can be placed.

    The sad consequence for us though is that comments don't "belong" anywhere.
    This is why this function generates simple parentless Leaf objects for
    comments.  We simply don't know what the correct parent should be.

    No matter though, we can live without this.  We really only need to
    differentiate between inline and standalone comments.  The latter don't
    share the line with any code.

    Inline comments are emitted as regular token.COMMENT leaves.  Standalone
    are emitted with a fake STANDALONE_COMMENT token identifier.
    """
    total_consumed = 0
    for pc in list_comments(
        leaf.prefix, is_endmarker=leaf.type == token.ENDMARKER, mode=mode
    ):
        total_consumed = pc.consumed
        prefix = make_simple_prefix(pc.newlines, pc.form_feed)
        yield Leaf(pc.type, pc.value, prefix=prefix)
    normalize_trailing_prefix(leaf, total_consumed)


@lru_cache(maxsize=4096)
def list_comments(prefix: str, *, is_endmarker: bool, mode: Mode) -> list[ProtoComment]:
    """Return a list of :class:`ProtoComment` objects parsed from the given `prefix`."""
    result: list[ProtoComment] = []
    if not prefix or "#" not in prefix:
        return result

    consumed = 0
    nlines = 0
    ignored_lines = 0
    form_feed = False
    for index, full_line in enumerate(re.split("\r?\n|\r", prefix)):
        consumed += len(full_line) + 1  # adding the length of the split '\n'
        match = re.match(r"^(\s*)(\S.*|)$", full_line)
        assert match
        whitespace, line = match.groups()
        if not line:
            nlines += 1
            if "\f" in full_line:
                form_feed = True
        if not line.startswith("#"):
            # Escaped newlines outside of a comment are not really newlines at
            # all. We treat a single-line comment following an escaped newline
            # as a simple trailing comment.
            if line.endswith("\\"):
                ignored_lines += 1
            continue

        if index == ignored_lines and not is_endmarker:
            comment_type = token.COMMENT  # simple trailing comment
        else:
            comment_type = STANDALONE_COMMENT
        comment = make_comment(line, mode=mode)
        result.append(
            ProtoComment(
                type=comment_type,
                value=comment,
                newlines=nlines,
                consumed=consumed,
                form_feed=form_feed,
                leading_whitespace=whitespace,
            )
        )
        form_feed = False
        nlines = 0
    return result


def normalize_trailing_prefix(leaf: LN, total_consumed: int) -> None:
    """Normalize the prefix that's left over after generating comments.

    Note: don't use backslashes for formatting or you'll lose your voting rights.
    """
    remainder = leaf.prefix[total_consumed:]
    if "\\" not in remainder:
        nl_count = remainder.count("\n")
        form_feed = "\f" in remainder and remainder.endswith("\n")
        leaf.prefix = make_simple_prefix(nl_count, form_feed)
        return

    leaf.prefix = ""


def make_comment(content: str, mode: Mode) -> str:
    """Return a consistently formatted comment from the given `content` string.

    All comments (except for "##", "#!", "#:", '#'") should have a single
    space between the hash sign and the content.

    If `content` didn't start with a hash sign, one is provided.
    """
    content = content.rstrip()
    if not content:
        return "#"

    if content[0] == "#":
        content = content[1:]
    if (
        content
        and content[0] == "\N{NO-BREAK SPACE}"
        and not is_type_comment_string("# " + content.lstrip(), mode=mode)
    ):
        content = " " + content[1:]  # Replace NBSP by a simple space
    if (
        Preview.standardize_type_comments in mode
        and content
        and "\N{NO-BREAK SPACE}" not in content
        and is_type_comment_string("#" + content, mode=mode)
    ):
        type_part, value_part = content.split(":", 1)
        content = type_part.strip() + ": " + value_part.strip()

    if content and content[0] not in COMMENT_EXCEPTIONS:
        content = " " + content
    return "#" + content


def normalize_fmt_off(
    node: Node, mode: Mode, lines: Collection[tuple[int, int]]
) -> None:
    """Convert content between `# fmt: off`/`# fmt: on` into standalone comments."""
    try_again = True
    while try_again:
        try_again = convert_one_fmt_off_pair(node, mode, lines)


def convert_one_fmt_off_pair(
    node: Node, mode: Mode, lines: Collection[tuple[int, int]]
) -> bool:
    """Convert content of a single `# fmt: off`/`# fmt: on` into a standalone comment.

    Returns True if a pair was converted.
    """
    for leaf in node.leaves():
        previous_consumed = 0
        for comment in list_comments(leaf.prefix, is_endmarker=False, mode=mode):
            is_fmt_off = comment.value in FMT_OFF
            is_fmt_skip = _contains_fmt_skip_comment(comment.value, mode)
            if (not is_fmt_off and not is_fmt_skip) or (
                # Invalid use when `# fmt: off` is applied before a closing bracket.
                is_fmt_off
                and leaf.type in CLOSING_BRACKETS
            ):
                previous_consumed = comment.consumed
                continue
            # We only want standalone comments. If there's no previous leaf or
            # the previous leaf is indentation, it's a standalone comment in
            # disguise.
            if comment.type != STANDALONE_COMMENT:
                prev = preceding_leaf(leaf)
                if prev:
                    if is_fmt_off and prev.type not in WHITESPACE:
                        continue
                    if is_fmt_skip and prev.type in WHITESPACE:
                        continue

            ignored_nodes = list(generate_ignored_nodes(leaf, comment, mode))
            if not ignored_nodes:
                continue

            first = ignored_nodes[0]  # Can be a container node with the `leaf`.
            parent = first.parent
            prefix = first.prefix
            if comment.value in FMT_OFF:
                first.prefix = prefix[comment.consumed :]
            if is_fmt_skip:
                first.prefix = ""
                standalone_comment_prefix = prefix
            else:
                standalone_comment_prefix = (
                    prefix[:previous_consumed] + "\n" * comment.newlines
                )
            hidden_value = "".join(str(n) for n in ignored_nodes)
            comment_lineno = leaf.lineno - comment.newlines
            if comment.value in FMT_OFF:
                fmt_off_prefix = ""
                if len(lines) > 0 and not any(
                    line[0] <= comment_lineno <= line[1] for line in lines
                ):
                    # keeping indentation of comment by preserving original whitespaces.
                    fmt_off_prefix = prefix.split(comment.value)[0]
                    if "\n" in fmt_off_prefix:
                        fmt_off_prefix = fmt_off_prefix.split("\n")[-1]
                standalone_comment_prefix += fmt_off_prefix
                hidden_value = comment.value + "\n" + hidden_value
            if is_fmt_skip:
                hidden_value += comment.leading_whitespace + comment.value
            if hidden_value.endswith("\n"):
                # That happens when one of the `ignored_nodes` ended with a NEWLINE
                # leaf (possibly followed by a DEDENT).
                hidden_value = hidden_value[:-1]
            first_idx: Optional[int] = None
            for ignored in ignored_nodes:
                index = ignored.remove()
                if first_idx is None:
                    first_idx = index
            assert parent is not None, "INTERNAL ERROR: fmt: on/off handling (1)"
            assert first_idx is not None, "INTERNAL ERROR: fmt: on/off handling (2)"
            parent.insert_child(
                first_idx,
                Leaf(
                    STANDALONE_COMMENT,
                    hidden_value,
                    prefix=standalone_comment_prefix,
                    fmt_pass_converted_first_leaf=first_leaf_of(first),
                ),
            )
            return True

    return False


def generate_ignored_nodes(
    leaf: Leaf, comment: ProtoComment, mode: Mode
) -> Iterator[LN]:
    """Starting from the container of `leaf`, generate all leaves until `# fmt: on`.

    If comment is skip, returns leaf only.
    Stops at the end of the block.
    """
    if _contains_fmt_skip_comment(comment.value, mode):
        yield from _generate_ignored_nodes_from_fmt_skip(leaf, comment, mode)
        return
    container: Optional[LN] = container_of(leaf)
    while container is not None and container.type != token.ENDMARKER:
        if is_fmt_on(container, mode=mode):
            return

        # fix for fmt: on in children
        if children_contains_fmt_on(container, mode=mode):
            for index, child in enumerate(container.children):
                if isinstance(child, Leaf) and is_fmt_on(child, mode=mode):
                    if child.type in CLOSING_BRACKETS:
                        # This means `# fmt: on` is placed at a different bracket level
                        # than `# fmt: off`. This is an invalid use, but as a courtesy,
                        # we include this closing bracket in the ignored nodes.
                        # The alternative is to fail the formatting.
                        yield child
                    return
                if (
                    child.type == token.INDENT
                    and index < len(container.children) - 1
                    and children_contains_fmt_on(
                        container.children[index + 1], mode=mode
                    )
                ):
                    # This means `# fmt: on` is placed right after an indentation
                    # level, and we shouldn't swallow the previous INDENT token.
                    return
                if children_contains_fmt_on(child, mode=mode):
                    return
                yield child
        else:
            if container.type == token.DEDENT and container.next_sibling is None:
                # This can happen when there is no matching `# fmt: on` comment at the
                # same level as `# fmt: on`. We need to keep this DEDENT.
                return
            yield container
            container = container.next_sibling


def _find_compound_statement_context(
    parent: Optional[LN], mode: Mode
) -> Optional[Node]:
    """Return the body node of a compound statement if we should respect fmt: skip.

    This handles one-line compound statements like:
        if condition: body  # fmt: skip

    When Black expands such statements, they temporarily look like:
        if condition:
            body  # fmt: skip

    In both cases, we want to return the body node (either the simple_stmt directly
    or the suite containing it).
    """
    if Preview.fix_fmt_skip_in_one_liners not in mode:
        return None

    if parent is None or parent.type != syms.simple_stmt:
        return None

    assert isinstance(parent, Node)

    # Case 1: Expanded form after Black's initial formatting pass.
    # The one-liner has been split across multiple lines:
    #     if True:
    #         print("a"); print("b")  # fmt: skip
    # Structure: compound_stmt -> suite -> simple_stmt
    if (
        isinstance(parent.parent, Node)
        and parent.parent.type == syms.suite
        and isinstance(parent.parent.parent, Node)
        and parent.parent.parent.type in _COMPOUND_STATEMENTS
    ):
        return parent.parent

    # Case 2: Original one-line form from the input source.
    # The statement is still on a single line:
    #     if True: print("a"); print("b")  # fmt: skip
    # Structure: compound_stmt -> simple_stmt
    if (
        isinstance(parent.parent, Node)
        and parent.parent.type in _COMPOUND_STATEMENTS
    ):
        return parent

    return None


def _should_keep_compound_statement_inline(
    body_node: Node, simple_stmt_parent: Node
) -> bool:
    """Check if a compound statement should be kept on one line.

    Returns True only for compound statements with semicolon-separated bodies,
    like: if True: print("a"); print("b")  # fmt: skip
    """
    # Check if there are semicolons in the body
    for leaf in body_node.leaves():
        if leaf.type == token.SEMI:
            # Verify it's a single-line body (one simple_stmt)
            if body_node.type == syms.suite:
                # After formatting: check suite has one simple_stmt child
                simple_stmts = [
                    child
                    for child in body_node.children
                    if child.type == syms.simple_stmt
                ]
                return len(simple_stmts) == 1 and simple_stmts[0] is simple_stmt_parent
            else:
                # Original form: body_node IS the simple_stmt
                return body_node is simple_stmt_parent
    return False


def _get_compound_statement_header(body_node: Node, simple_stmt_parent: Node) -> list[LN]:
    """Get header nodes for a compound statement that should be preserved inline."""
    if not _should_keep_compound_statement_inline(body_node, simple_stmt_parent):
        return []

    # Get the compound statement (parent of body)
    compound_stmt = body_node.parent
    if compound_stmt is None or compound_stmt.type not in _COMPOUND_STATEMENTS:
        return []

    # Collect all header leaves before the body
    header_leaves: list[LN] = []
    for child in compound_stmt.children:
        if child is body_node:
            break
        if isinstance(child, Leaf):
            if child.type not in (token.NEWLINE, token.INDENT):
                header_leaves.append(child)
        else:
            header_leaves.extend(child.leaves())
    return header_leaves


def _generate_ignored_nodes_from_fmt_skip(
    leaf: Leaf, comment: ProtoComment, mode: Mode
) -> Iterator[LN]:
    """Generate all leaves that should be ignored by the `# fmt: skip` from `leaf`."""
    prev_sibling = leaf.prev_sibling
    parent = leaf.parent
    ignored_nodes: list[LN] = []
    # Need to properly format the leaf prefix to compare it to comment.value,
    # which is also formatted
    comments = list_comments(leaf.prefix, is_endmarker=False, mode=mode)
    if not comments or comment.value != comments[0].value:
        return
    if prev_sibling is not None:
        leaf.prefix = leaf.prefix[comment.consumed :]

        if Preview.fix_fmt_skip_in_one_liners not in mode:
            siblings = [prev_sibling]
            while (
                "\n" not in prev_sibling.prefix
                and prev_sibling.prev_sibling is not None
            ):
                prev_sibling = prev_sibling.prev_sibling
                siblings.insert(0, prev_sibling)
            yield from siblings
            return

        # Generates the nodes to be ignored by `fmt: skip`.

        # Nodes to ignore are the ones on the same line as the
        # `# fmt: skip` comment, excluding the `# fmt: skip`
        # node itself.

        # Traversal process (starting at the `# fmt: skip` node):
        # 1. Move to the `prev_sibling` of the current node.
        # 2. If `prev_sibling` has children, go to its rightmost leaf.
        # 3. If there's no `prev_sibling`, move up to the parent
        # node and repeat.
        # 4. Continue until:
        #    a. You encounter an `INDENT` or `NEWLINE` node (indicates
        #       start of the line).
        #    b. You reach the root node.

        # Include all visited LEAVES in the ignored list, except INDENT
        # or NEWLINE leaves.

        current_node = prev_sibling
        ignored_nodes = [current_node]
        if current_node.prev_sibling is None and current_node.parent is not None:
            current_node = current_node.parent
        while "\n" not in current_node.prefix and current_node.prev_sibling is not None:
            leaf_nodes = list(current_node.prev_sibling.leaves())
            current_node = leaf_nodes[-1] if leaf_nodes else current_node

            if current_node.type in (token.NEWLINE, token.INDENT):
                current_node.prefix = ""
                break

            ignored_nodes.insert(0, current_node)

            if current_node.prev_sibling is None and current_node.parent is not None:
                current_node = current_node.parent
        # Special handling for compound statements with semicolon-separated bodies
        body_node = _find_compound_statement_context(parent, mode)
        if body_node is not None and isinstance(parent, Node):
            header_nodes = _get_compound_statement_header(body_node, parent)
            if header_nodes:
                ignored_nodes = header_nodes + ignored_nodes

        yield from ignored_nodes
    elif (
        parent is not None and parent.type == syms.suite and leaf.type == token.NEWLINE
    ):
        # The `# fmt: skip` is on the colon line of the if/while/def/class/...
        # statements. The ignored nodes should be previous siblings of the
        # parent suite node.
        leaf.prefix = ""
        parent_sibling = parent.prev_sibling
        while parent_sibling is not None and parent_sibling.type != syms.suite:
            ignored_nodes.insert(0, parent_sibling)
            parent_sibling = parent_sibling.prev_sibling
        # Special case for `async_stmt` where the ASYNC token is on the
        # grandparent node.
        grandparent = parent.parent
        if (
            grandparent is not None
            and grandparent.prev_sibling is not None
            and grandparent.prev_sibling.type == token.ASYNC
        ):
            ignored_nodes.insert(0, grandparent.prev_sibling)
        yield from iter(ignored_nodes)


def is_fmt_on(container: LN, mode: Mode) -> bool:
    """Determine whether formatting is switched on within a container.
    Determined by whether the last `# fmt:` comment is `on` or `off`.
    """
    fmt_on = False
    for comment in list_comments(container.prefix, is_endmarker=False, mode=mode):
        if comment.value in FMT_ON:
            fmt_on = True
        elif comment.value in FMT_OFF:
            fmt_on = False
    return fmt_on


def children_contains_fmt_on(container: LN, mode: Mode) -> bool:
    """Determine if children have formatting switched on."""
    for child in container.children:
        leaf = first_leaf_of(child)
        if leaf is not None and is_fmt_on(leaf, mode=mode):
            return True

    return False


def contains_pragma_comment(comment_list: list[Leaf]) -> bool:
    """
    Returns:
        True iff one of the comments in @comment_list is a pragma used by one
        of the more common static analysis tools for python (e.g. mypy, flake8,
        pylint).
    """
    for comment in comment_list:
        if comment.value.startswith(("# type:", "# noqa", "# pylint:")):
            return True

    return False


def _contains_fmt_skip_comment(comment_line: str, mode: Mode) -> bool:
    """
    Checks if the given comment contains FMT_SKIP alone or paired with other comments.
    Matching styles:
      # fmt:skip                           <-- single comment
      # noqa:XXX # fmt:skip # a nice line  <-- multiple comments (Preview)
      # pylint:XXX; fmt:skip               <-- list of comments (; separated, Preview)
    """
    semantic_comment_blocks = [
        comment_line,
        *[
            _COMMENT_PREFIX + comment.strip()
            for comment in comment_line.split(_COMMENT_PREFIX)[1:]
        ],
        *[
            _COMMENT_PREFIX + comment.strip()
            for comment in comment_line.strip(_COMMENT_PREFIX).split(
                _COMMENT_LIST_SEPARATOR
            )
        ],
    ]

    return any(comment in FMT_SKIP for comment in semantic_comment_blocks)

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