6963313779

Committed 22 Nov 2023 10:24PM UTC coverage: 90.246% (-0.05%) from 90.293%

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overlookmotel

Commit Message

Record frozen function names in instrumentation

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83.62

/lib/instrument/visitors/function.js

/* --------------------
 * livepack module
 * Code instrumentation visitor for functions
 * ------------------*/

'use strict';

// Export
module.exports = {
        ArrowFunctionExpression,
        FunctionDeclaration,
        FunctionExpression,
        createAndEnterFunctionOrClassNameBlock,
        visitFunctionOrMethod,
        visitFunctionParamsAndBody,
        removeUnnecessaryUseStrictDirectives,
        createFunction,
        getFunctionType,
        escapeFilename,
        withStrictModeState,
        hoistSloppyFunctionDeclarations,
        instrumentFunctionOrClassConstructor,
        insertTrackerComment,
        createFunctionInfoFunction
};

// Modules
const mapValues = require('lodash/mapValues'),
        t = require('@babel/types');

// Imports
const Statement = require('./statement.js'),
        Expression = require('./expression.js'),
        {IdentifierLet, AssigneeLet} = require('./assignee.js'),
        {visitKey, visitKeyContainer} = require('../visit.js'),
        {
                createBlock, createAndEnterBlock, createBinding, createThisBinding, createArgumentsBinding,
                createNewTargetBinding, getOrCreateExternalVar
        } = require('../blocks.js'),
        {insertTrackerCodeIntoFunctionBody, insertTrackerCodeIntoFunctionParams} = require('../tracking.js'),
        {createFnInfoVarNode} = require('../internalVars.js'),
        {insertComment, hasUseStrictDirective, stringLiteralWithSingleQuotes} = require('../utils.js'),
        {combineArraysWithDedup} = require('../../shared/functions.js'),
        {
                FN_TYPE_FUNCTION, FN_TYPE_ASYNC_FUNCTION, FN_TYPE_GENERATOR_FUNCTION,
                FN_TYPE_ASYNC_GENERATOR_FUNCTION, TRACKER_COMMENT_PREFIX,
                CONST_VIOLATION_NEEDS_VAR, CONST_VIOLATION_NEEDS_NO_VAR
        } = require('../../shared/constants.js');

// Exports

/**
 * Visitor for arrow function.
 * @param {Object} node - Arrow function AST node
 * @param {Object} state - State object
 * @param {Object|Array} parent - Parent AST node/container
 * @param {string|number} key - Node's key on parent AST node/container
 * @returns {undefined}
 */
function ArrowFunctionExpression(node, state, parent, key) {
        // Tracker comment is inserted later to avoid it getting relocated if function has complex params
        // which are later relocated to inside function body
        visitFunction(node, parent, key, undefined, false, node.body.type === 'BlockStatement', state);
}

/**
 * Visitor for function declaration.
 * @param {Object} node - Function declaration AST node
 * @param {Object} state - State object
 * @param {Object|Array} parent - Parent AST node/container
 * @param {string|number} key - Node's key on parent AST node/container
 * @returns {undefined}
 */
function FunctionDeclaration(node, state, parent, key) {
        // Visit function
        const fnName = node.id.name;
        const fn = visitFunction(node, parent, key, fnName, true, true, state);

        // Create binding for function name
        // TODO: Whether the value of the function is hoisted depends on whether is a top level statement
        // (including in a labeled statement)
        // `() => { console.log(typeof x); function x() {} }` -> Logs 'function'
        // `() => { console.log(typeof x); q: function x() {} }` -> Logs 'function'
        // `() => { console.log(typeof x); if (true) function x() {} }` -> Logs 'undefined'
        const {currentBlock: block, currentHoistBlock: hoistBlock} = state;
        let binding = block.bindings[fnName];
        if (!binding) {
                const isTopLevel = block === hoistBlock;
                binding = createBinding(block, fnName, {isVar: isTopLevel, isFrozenName: true}, state);
                state.currentFunction?.reservedVarNames.add(fnName);

                // If is a sloppy-mode function declaration which may need to be hoisted, record that.
                // Determine whether to hoist after 1st pass is complete, once all other bindings created.
                if (!isTopLevel && !state.isStrict && !node.async && !node.generator) {
                        state.sloppyFunctionDeclarations.push({
                                varName: fnName,
                                binding,
                                block,
                                hoistBlock,
                                parentFn: state.currentFunction
                        });
                }
        } else if (!binding.isFrozenName) {
                // Existing binding is a `var` declaration.
                // Flag binding as frozen so `var` declarations' identifiers don't get renamed.
                binding.isFrozenName = true;
                binding.trails.length = 0;
        }

        // Insert tracker comment
        insertFunctionDeclarationOrExpressionTrackerComment(fn, node, state);
}

/**
 * Visitor for function expression.
 * @param {Object} node - Function expression AST node
 * @param {Object} state - State object
 * @param {Object|Array} parent - Parent AST node/container
 * @param {string|number} key - Node's key on parent AST node/container
 * @returns {undefined}
 */
function FunctionExpression(node, state, parent, key) {
        // If not anonymous, create and enter name block
        let nameBlock, fnName;
        const idNode = node.id;
        if (idNode) {
                fnName = idNode.name;
                nameBlock = createAndEnterFunctionOrClassNameBlock(fnName, true, state);
        }

        // Visit function
        const fn = visitFunction(node, parent, key, fnName, true, true, state);

        if (nameBlock) {
                // Exit name block
                state.currentBlock = nameBlock.parent;

                // If contains `eval()`, change function ID to make name block be considered internal to function.
                // An external var representing the function is pointless as its name will be frozen anyway
                // due to being in scope of the `eval()`.
                if (fn.containsEval) fn.id = nameBlock.id;
        }

        // Insert tracker comment
        insertFunctionDeclarationOrExpressionTrackerComment(fn, node, state);
}

/**
 * Create block for function/class name accessed within the function/class.
 * @param {string} fnName - Function name
 * @param {boolean} isSilentConst - `true` if assignment to function name silently fails in sloppy mode
 * @param {Object} state - State object
 * @returns {Object} - Block object
 */
function createAndEnterFunctionOrClassNameBlock(fnName, isSilentConst, state) {
        const block = createAndEnterBlock(fnName, false, state);
        createBinding(block, fnName, {isConst: true, isSilentConst, isFrozenName: true}, state);
        state.currentFunction?.reservedVarNames.add(fnName);
        return block;
}

/**
 * Visit function declaration, function expression or arrow function.
 * @param {Object} node - Function declaration, function expression or arrow function AST node
 * @param {Object|Array} parent - Parent AST node/container
 * @param {string|number} key - Node's key on parent AST node/container
 * @param {string} [fnName] - Function name (`undefined` if unnamed)
 * @param {boolean} isFullFunction - `true` if is not arrow function
 * @param {boolean} hasBodyBlock - `true` if has body block (only arrow functions can not)
 * @param {Object} state - State object
 * @returns {Object} - Function object
 */
function visitFunction(node, parent, key, fnName, isFullFunction, hasBodyBlock, state) {
        return withStrictModeState(
                node, hasBodyBlock, state,
                (isStrict, isEnteringStrict) => visitFunctionOrMethod(
                        node, parent, key, fnName, isStrict, isEnteringStrict, isFullFunction, hasBodyBlock, state
                )
        );
}

/**
 * Visit function or method.
 * @param {Object} fnNode - Function declaration, function expression, arrow function,
 *   class method, class private method or object method AST node
 * @param {Object|Array} parent - Parent AST node/container
 * @param {string|number} key - Node's key on parent AST node/container
 * @param {string} [fnName] - Function name (`undefined` if unnamed)
 * @param {boolean} isStrict - `true` if function is strict mode
 * @param {boolean} isEnteringStrict - `true` if function is strict mode and parent is sloppy mode
 * @param {boolean} isFullFunction - `true` if is not arrow function
 * @param {boolean} hasBodyBlock - `true` if has body block (only arrow functions can not)
 * @param {Object} state - State object
 * @returns {Object} - Function object
 */
function visitFunctionOrMethod(
        fnNode, parent, key, fnName, isStrict, isEnteringStrict, isFullFunction, hasBodyBlock, state
) {
        // Create params block. If is full function, create bindings for `this` + `new.target`.
        const paramsBlock = createAndEnterBlock(fnName, false, state);
        let parentThisBlock;
        if (isFullFunction) {
                createThisBinding(paramsBlock);
                createNewTargetBinding(paramsBlock);
                parentThisBlock = state.currentThisBlock;
                state.currentThisBlock = paramsBlock;
        }

        // Create and enter function
        const fn = createFunction(paramsBlock.id, fnNode, isStrict, state);
        state.currentFunction = fn;
        const parentTrail = state.trail;
        state.trail = [];

        // Create body block or make params block a vars block
        let bodyBlock;
        if (hasBodyBlock) {
                bodyBlock = createBlock(fnName, true, state);
                paramsBlock.varsBlock = bodyBlock;
        } else {
                paramsBlock.varsBlock = paramsBlock;
        }

        // Visit params + body
        const argNames = visitFunctionParamsAndBody(fn, fnNode, paramsBlock, bodyBlock, isStrict, state);

        // If is full function, create binding for `arguments` in params block.
        // Param called `arguments` takes precedence.
        if (isFullFunction) {
                if (!paramsBlock.bindings.arguments) createArgumentsBinding(paramsBlock, isStrict, argNames);
                state.currentThisBlock = parentThisBlock;
        }

        // Serialize AST
        fn.astJson = serializeFunctionAst(fnNode, hasBodyBlock, isStrict, isEnteringStrict);

        // Exit function
        state.currentBlock = paramsBlock.parent;
        state.currentFunction = fn.parent;
        state.trail = parentTrail;

        // Temporarily remove from AST so is not included in parent function's serialized AST
        parent[key] = null;

        // Queue instrumentation of function in 2nd pass
        state.secondPass(instrumentFunction, fnNode, fn, parent, key, paramsBlock, bodyBlock, state);

        return fn;
}

/**
 * Visit function params and body.
 * Caller must ensure `state.currentBlock` is params block,
 * and `state.currentThisBlock` is params block if is a full function.
 * Caller must set `state.currentBlock` and `state.currentThisBlock` back afterwards.
 * @param {Object} fn - Function object
 * @param {Object} fnNode - Function/method AST node
 * @param {Object} paramsBlock - Block object for function params
 * @param {Object} [bodyBlock] - Block object for body block, if function's body is a statement block
 * @param {boolean} isStrict - `true` if function is strict mode
 * @param {Object} state - State object
 * @returns {Array<string>} - Array of argument names which are linked to argument vars.
 *   Will be empty array if strict mode, or arguments are not all simple identifiers.
 */
function visitFunctionParamsAndBody(fn, fnNode, paramsBlock, bodyBlock, isStrict, state) {
        // Visit params and find first complex param (i.e. param which is not just an identifier).
        // Do not consider `...x` to be complex.
        // Also get array of params which are linked to `arguments`.
        // i.e. `((x) => { arguments[0] = 2; return x; })(1) === 2`
        // `arguments` is only linked in sloppy mode functions with no complex params.
        const argNames = [];
        let hasLinkedArguments = !isStrict,
                firstComplexParamIndex;
        visitKeyContainer(fnNode, 'params', (paramNode, _state, paramNodes, index) => {
                if (paramNode.type === 'Identifier') {
                        if (hasLinkedArguments) argNames.push(paramNode.name);
                        IdentifierLet(paramNode, state, paramNodes, index);
                } else {
                        if (firstComplexParamIndex === undefined) {
                                hasLinkedArguments = false;
                                argNames.length = 0;
                                if (paramNode.type !== 'RestElement' || paramNode.argument.type !== 'Identifier') {
                                        firstComplexParamIndex = index;

                                        // Make params block the vars block. Tracker call and scope ID var will go in params.
                                        if (bodyBlock) paramsBlock.varsBlock = bodyBlock.varsBlock = paramsBlock;
                                }
                        }

                        AssigneeLet(paramNode, state, paramNodes, index);
                }
        }, state);

        // Record index of first complex param
        fn.firstComplexParamIndex = firstComplexParamIndex;

        // Visit body
        if (bodyBlock) {
                state.currentBlock = bodyBlock;
                const parentHoistBlock = state.currentHoistBlock;
                state.currentHoistBlock = bodyBlock;
                visitKey(fnNode, 'body', FunctionBodyBlock, state);
                state.currentHoistBlock = parentHoistBlock;
        } else {
                visitKey(fnNode, 'body', Expression, state);
        }

        // Return array of params which are linked to `arguments`
        return argNames;
}

/**
 * Visitor for function body block.
 * @param {Object} node - Function body block AST node
 * @param {Object} state - State object
 * @returns {undefined}
 */
function FunctionBodyBlock(node, state) {
        visitKeyContainer(node, 'body', Statement, state);
}

/**
 * Serialize function AST to JSON.
 * Remove unnecessary 'use strict' directives if present.
 * Do not mutate the node passed in, to ensure these changes only affect the serialized AST,
 * and not the instrumented output.
 * @param {Object} fnNode - Function AST node
 * @param {boolean} hasBodyBlock - `true` if has body block (only arrow functions can not)
 * @param {boolean} isStrict - `true` if function is strict mode
 * @param {boolean} isEnteringStrict - `true` if function transitions into strict mode
 *   (and therefore needs to retain a 'use strict' directive)
 * @returns {string} - Function AST as JSON
 */
function serializeFunctionAst(fnNode, hasBodyBlock, isStrict, isEnteringStrict) {
        // Remove unnecessary 'use strict' directives
        if (hasBodyBlock && isStrict) {
                const alteredFnNode = removeUnnecessaryUseStrictDirectives(fnNode, !isEnteringStrict);
                if (alteredFnNode) fnNode = alteredFnNode;
        }

        // Stringify AST to JSON
        return JSON.stringify(fnNode);
}

/**
 * Remove unnecessary 'use strict' directives from function body.
 * Relocate any comments from deleted directives.
 * Do not mutate input - clone if needs alteration.
 * Return `undefined` if no alteration necessary.
 * @param {Object} fnNode - Function AST node
 * @param {boolean} needsNoDirective - `true` if function already strict mode from outer environment
 * @returns {Object|undefined} - Altered function AST node, or `undefined` if no directives removed
 */
function removeUnnecessaryUseStrictDirectives(fnNode, needsNoDirective) {
        // If no directives, return `undefined`
        let bodyNode = fnNode.body;
        const directiveNodes = bodyNode.directives;
        if (directiveNodes.length === 0) return undefined;

        // Remove unnecessary directives
        const newDirectiveNodes = [],
                commentNodes = [];
        for (let directiveNode of directiveNodes) {
                if (directiveNode.value.value === 'use strict') {
                        if (needsNoDirective) {
                                commentNodes.push(
                                        ...(directiveNode.leadingComments || []),
                                        ...(directiveNode.trailingComments || [])
                                );
                                continue;
                        }
                        needsNoDirective = true;
                }

                // Add any comments removed from previous directives
                if (commentNodes.length !== 0) {
                        directiveNode = {
                                ...directiveNode,
                                leadingComments: combineArraysWithDedup(commentNodes, directiveNode.leadingComments)
                        };
                        commentNodes.length = 0;
                }

                newDirectiveNodes.push(directiveNode);
        }

        // If no directives need to be removed, return `undefined`
        if (newDirectiveNodes.length === directiveNodes.length) return undefined;

        // Clone function node
        bodyNode = {...bodyNode, directives: newDirectiveNodes};
        fnNode = {...fnNode, body: bodyNode};

        // Add any remaining comments to first statement / last directive / function body
        if (commentNodes.length !== 0) {
                let statementNodes = bodyNode.body;
                if (statementNodes.length !== 0) {
                        statementNodes = bodyNode.body = [...statementNodes];
                        const firstStatementNode = statementNodes[0];
                        statementNodes[0] = {
                                ...firstStatementNode,
                                leadingComments: combineArraysWithDedup(commentNodes, firstStatementNode.leadingComments)
                        };
                } else if (newDirectiveNodes.length !== 0) {
                        const lastDirectiveNode = newDirectiveNodes[newDirectiveNodes.length - 1];
                        newDirectiveNodes[newDirectiveNodes.length - 1] = {
                                ...lastDirectiveNode,
                                trailingComments: combineArraysWithDedup(lastDirectiveNode.trailingComments, commentNodes)
                        };
                } else {
                        bodyNode.innerComments = combineArraysWithDedup(bodyNode.innerComments, commentNodes);
                }
        }

        // Return clone of function node
        return fnNode;
}

/**
 * Create object representing function.
 * @param {number} id - Function ID
 * @param {Object} node - Function/method/class AST node
 * @param {boolean} isStrict - `true` if function is strict mode
 * @param {Object} state - State object
 * @returns {Object} - Function object
 */
function createFunction(id, node, isStrict, state) {
        const parentFunction = state.currentFunction;
        const fn = {
                id,
                node,
                astJson: undefined,
                isStrict,
                parent: parentFunction,
                children: [],
                trail: parentFunction ? [...state.trail] : undefined,
                bindings: [],
                externalVars: new Map(), // Keyed by block
                scopes: undefined,
                globalVarNames: new Set(),
                reservedVarNames: new Set(),
                amendments: [],
                superIsProto: false,
                containsEval: false,
                containsImport: false,
                hasSuperClass: false,
                firstSuperStatementIndex: undefined,
                returnsSuper: false,
                firstComplexParamIndex: undefined
        };

        if (parentFunction) parentFunction.children.push(fn);

        state.functions.push(fn);
        state.fileContainsFunctionsOrEval = true;

        return fn;
}

/**
 * Get type code for function.
 * @param {Object} fnNode - Function AST node
 * @returns {string} - Function type code
 */
function getFunctionType(fnNode) {
        return fnNode.async
                ? fnNode.generator
                        ? FN_TYPE_ASYNC_GENERATOR_FUNCTION
                        : FN_TYPE_ASYNC_FUNCTION
                : fnNode.generator
                        ? FN_TYPE_GENERATOR_FUNCTION
                        : FN_TYPE_FUNCTION;
}

/**
 * Escape filename so it can be safely included in tracker comment.
 * @param {string} filename - File path
 * @returns {string} - Filename escaped
 */
function escapeFilename(filename) {
        // Encode filename as JSON to escape non-ascii chars.
        // Convert `*/` to `*\/` so does not terminate comment early.
        // `JSON.parse('"*\/"')` is `'*/'` so it needs no special unescaping.
        return JSON.stringify(filename).slice(1, -1).replace(/\*\//g, '*\\/');
}

/**
 * Determine if function is strict mode. If it is, set `state.isStrict` flag.
 * Call visitor with strict/sloppy mode flags.
 * @param {Object} fnNode - Function or method AST node
 * @param {boolean} hasBodyBlock - `true` if has body block (only arrow functions can not)
 * @param {Object} state - State object
 * @param {Function} visit - Visitor function
 * @returns {*} - Visitor function's return value
 */
function withStrictModeState(fnNode, hasBodyBlock, state, visit) {
        // Get if strict mode
        let {isStrict} = state,
                isEnteringStrict = false;
        if (!isStrict && hasBodyBlock && hasUseStrictDirective(fnNode.body)) {
                isStrict = isEnteringStrict = state.isStrict = true;
        }

        // Call visitor
        const res = visit(isStrict, isEnteringStrict);

        // If entered strict mode, exit it again
        if (isEnteringStrict) state.isStrict = false;

        // Return visitor's return value
        return res;
}

/**
 * Hoist sloppy function declarations if they can be hoisted.
 * Function declarations are hoisted to the top block in parent function body or program
 * if they are defined in sloppy mode (i.e. outside environment is sloppy mode, regardless of
 * whether function itself strict mode) and they are not async or generator functions.
 *
 * They can only be hoisted if:
 *   1. No `const`, `let` or class declaration with same name in block they'd be hoisted to.
 *   2. No parameter in parent function with same name.
 *   3. No other bindings in intermediate blocks
 *      (including other function declarations which are themselves hoisted)
 *
 * When a function declaration is hoisted, it produces two separate bindings:
 *   1. Binding in block where originally defined.
 *   2. Binding in block it's hoisted to.
 *
 * See https://github.com/babel/babel/pull/14203#issuecomment-1038187168
 *
 * @param {Object} state - State object
 * @returns {undefined}
 */
function hoistSloppyFunctionDeclarations(state) {
        for (const declaration of state.sloppyFunctionDeclarations) {
                hoistSloppyFunctionDeclaration(declaration);
        }
}

/**
 * Hoist function declaration, if it can be hoisted.
 * Should only be called for functions which:
 *   1. are not already in the top block in parent function / program
 *   2. are not async or generator functions
 *
 * @param {Object} declaration - Declaration object
 * @param {string} declaration.varName - Function name
 * @param {Object} declaration.binding - Binding object for binding in block where originally declared
 * @param {Object} declaration.block - Block object for block where originally declared
 * @param {Object} declaration.hoistBlock - Block object for block where could be hoisted to
 * @param {Object} [declaration.parentFn] - Function object for parent function
 * @returns {undefined}
 */
function hoistSloppyFunctionDeclaration(declaration) {
        const {varName, hoistBlock} = declaration;

        // Do not hoist if existing const, let or class declaration binding in hoist block
        const hoistBlockBinding = hoistBlock.bindings[varName];
        if (hoistBlockBinding && !hoistBlockBinding.isVar) return;

        // If parent function's params include var with same name, do not hoist.
        // NB: `hoistBlock.parent` here is either parent function params block or file block.
        // In CommonJS code, file block is CommonJS wrapper function's params, and in any other context
        // file block contains no bindings except `this`. So it's safe to treat as a params block in all cases.
        // NB: `paramsBlockBinding.argNames` check is to avoid the pseudo-param `arguments` blocking hoisting.
        const paramsBlockBinding = hoistBlock.parent.bindings[varName];
        if (paramsBlockBinding && !paramsBlockBinding.argNames) return;

        // If any binding in intermediate blocks, do not hoist.
        // NB: This includes function declarations which will be themselves hoisted.
        let inBetweenBlock = declaration.block.parent;
        while (inBetweenBlock !== hoistBlock) {
                if (inBetweenBlock.bindings[varName]) return;
                inBetweenBlock = inBetweenBlock.parent;
        }

        // Can be hoisted
        if (!hoistBlockBinding) {
                hoistBlock.bindings[varName] = {...declaration.binding, isVar: true};
        } else if (!hoistBlockBinding.isFrozenName) {
                // Existing binding is a `var` declaration.
                // Flag binding as frozen so `var` declarations' identifiers don't get renamed.
                hoistBlockBinding.isFrozenName = true;
                hoistBlockBinding.trails.length = 0;
        }
}

/**
 * Instrument function.
 * @param {Object} node - Function or method AST node
 * @param {Object} fn - Function object
 * @param {Object|Array} parent - Parent AST node/container
 * @param {string|number} key - Node's key on parent AST node/container
 * @param {Object} paramsBlock - Function's params block object
 * @param {Object} [bodyBlock] - Function's body block object (if it has one, arrow functions may not)
 * @param {Object} state - State object
 * @returns {undefined}
 */
function instrumentFunction(node, fn, parent, key, paramsBlock, bodyBlock, state) {
        // Restore to original place in AST
        parent[key] = node;

        instrumentFunctionOrClassConstructor(node, fn, paramsBlock, bodyBlock, state);

        if (node.type === 'ArrowFunctionExpression') insertArrowFunctionTrackerComment(fn, node, state);
}

/**
 * Instrument function, method or class constructor.
 *   - Insert `livepack_tracker()` call in function body.
 *   - Insert block vars (`livepack_scopeId`, `livepack_temp`) in function body or params.
 *   - Create function info function containing function AST, details of internal and external vars etc.
 *
 * @param {Object} node - Function, method, or class constructor AST node
 * @param {Object} fn - Function object
 * @param {Object} paramsBlock - Function's params block object
 * @param {Object} bodyBlock - Function's body block object
 * @param {Object} state - State object
 * @returns {undefined}
 */
function instrumentFunctionOrClassConstructor(node, fn, paramsBlock, bodyBlock, state) {
        // NB `bodyBlock` here may actually be params block if is an arrow function with no body.
        // Sort scopes in ascending order of block ID.
        const scopes = [...fn.externalVars].map(([block, vars]) => ({block, vars}))
                .sort((scope1, scope2) => (scope1.block.id > scope2.block.id ? 1 : -1));
        fn.scopes = scopes;

        // Add external vars to parent function where external to that function too
        const parentFunction = fn.parent;
        if (parentFunction) {
                // External vars
                const {id: parentFunctionId, externalVars: parentExternalVars} = parentFunction;
                for (const {block, vars} of scopes) {
                        if (block.id >= parentFunctionId) break;
                        for (const [varName, {binding}] of Object.entries(vars)) {
                                getOrCreateExternalVar(parentExternalVars, block, varName, binding);
                        }
                }
        }

        // Insert tracker call and block vars (`livepack_scopeId` and `livepack_temp`) into function.
        // If function has complex params, insert into params. Otherwise, into function body.
        const trackerNode = createTrackerCall(fn.id, scopes, state);

        const {firstComplexParamIndex} = fn;
        if (firstComplexParamIndex === undefined) {
                insertTrackerCodeIntoFunctionBody(node, paramsBlock, bodyBlock, trackerNode, state);
        } else {
                insertTrackerCodeIntoFunctionParams(
                        node, paramsBlock, bodyBlock, trackerNode, firstComplexParamIndex, state
                );
        }
}

/**
 * Create tracker call.
 * @param {number} fnId - Function ID
 * @param {Array<Object>} scopes - Array of scope objects in ascending order of block ID
 * @param {Object} state - State object
 * @returns {undefined}
 */
function createTrackerCall(fnId, scopes, state) {
        // `livepack_tracker(livepack_getFnInfo_3, () => [[livepack_scopeId_2, x]]);`
        return t.callExpression(state.trackerVarNode, [
                createFnInfoVarNode(fnId, state),
                t.arrowFunctionExpression([], t.arrayExpression(
                        scopes.map(scope => t.arrayExpression([
                                scope.block.varsBlock.scopeIdVarNode,
                                ...Object.values(scope.vars).map(blockVar => blockVar.binding.varNode)
                        ]))
                ))
        ]);
}

/**
 * Insert tracker comment into function declaration/expression.
 * @param {Object} fn - Function object
 * @param {Object} node - Function declaration or expression AST node
 * @param {Object} state - State object
 * @returns {undefined}
 */
function insertFunctionDeclarationOrExpressionTrackerComment(fn, node, state) {
        // Insert tracker comment before identifier, or before 1st param or before function body
        const commentHolderNode = node.id || (node.params.length !== 0 ? node.params[0] : node.body);
        insertTrackerComment(fn.id, getFunctionType(node), commentHolderNode, 'leading', state);
}

/**
 * Insert tracker comment into arrow function.
 * @param {Object} fn - Function object
 * @param {Object} node - Arrow function AST node
 * @param {Object} state - State object
 * @returns {undefined}
 */
function insertArrowFunctionTrackerComment(fn, node, state) {
        // Insert tracker comment before first param. If no params, before function body.
        const paramNodes = node.params;
        insertTrackerComment(
                fn.id, node.async ? FN_TYPE_ASYNC_FUNCTION : FN_TYPE_FUNCTION,
                paramNodes.length !== 0 ? paramNodes[0] : node.body, 'leading', state
        );
}

/**
 * Insert tracker comment.
 * @param {number} fnId - Function ID
 * @param {string} fnType - Function type
 * @param {Object} commentHolderNode - AST node to attach comment to
 * @param {string} commentType - 'leading' / 'inner' / 'trailing'
 * @param {Object} state - State object
 * @returns {undefined}
 */
function insertTrackerComment(fnId, fnType, commentHolderNode, commentType, state) {
        insertComment(
                commentHolderNode, commentType,
                `${TRACKER_COMMENT_PREFIX}${fnId};${fnType};${state.filenameEscaped}`
        );
}

/**
 * Create function info function containing function AST, details of internal and external vars etc.
 * @param {Object} fn - Function object
 * @param {Object} state - State object
 * @returns {Object} - AST node for function info function
 */
function createFunctionInfoFunction(fn, state) {
        // Compile internal vars and reserved var names
        const internalVars = Object.create(null),
                {reservedVarNames} = fn;
        for (const {name: varName, trails, isFrozenName} of fn.bindings) {
                if (isFrozenName) {
                        reservedVarNames.add(varName);
                } else {
                        const internalVar = internalVars[varName] || (internalVars[varName] = []);
                        internalVar.push(...trails);
                }
        }

        // Compile amendments.
        // Reverse order so deepest are first.
        // Remove the need for an internal var if binding has frozen name.
        let amendments;
        if (fn.amendments.length > 0) {
                amendments = fn.amendments.map(({type, blockId, trail, binding}) => {
                        if (type === CONST_VIOLATION_NEEDS_VAR && binding.isFrozenName) {
                                type = CONST_VIOLATION_NEEDS_NO_VAR;
                        }
                        return [type, blockId, ...trail];
                }).reverse();
        }

        // Create JSON function info string
        const {children} = fn;
        let argNames;
        let json = JSON.stringify({
                scopes: fn.scopes.map(({block, vars}) => ({
                        blockId: block.id,
                        blockName: block.name,
                        vars: mapValues(vars, (varProps, varName) => {
                                if (varName === 'arguments') argNames = varProps.binding.argNames;
                                return {
                                        isReadFrom: varProps.isReadFrom || undefined,
                                        isAssignedTo: varProps.isAssignedTo || undefined,
                                        isFrozenName: varProps.isFrozenName || undefined,
                                        isFrozenInternalName: varProps.binding.isFrozenName || undefined,
                                        trails: varProps.trails
                                };
                        })
                })),
                isStrict: fn.isStrict || undefined,
                superIsProto: fn.superIsProto || undefined,
                containsEval: fn.containsEval || undefined,
                containsImport: fn.containsImport || undefined,
                argNames,
                internalVars,
                reservedVarNames: reservedVarNames.size !== 0 ? [...reservedVarNames] : undefined,
                globalVarNames: fn.globalVarNames.size !== 0 ? [...fn.globalVarNames] : undefined,
                amendments,
                hasSuperClass: fn.hasSuperClass || undefined,
                firstSuperStatementIndex: fn.firstSuperStatementIndex,
                returnsSuper: fn.returnsSuper || undefined,
                childFns: children.map(childFn => childFn.trail)
        });

        // Add AST JSON to JSON
        json = `${json.slice(0, -1)},"ast":${fn.astJson}}`;

        // Create function returning JSON string and references to function info function for child fns.
        // Make output as single-quoted string for shorter output (not escaping every `"`).
        return t.functionDeclaration(createFnInfoVarNode(fn.id, state), [], t.blockStatement([
                t.returnStatement(t.arrayExpression([
                        stringLiteralWithSingleQuotes(json),
                        t.arrayExpression(children.map(childFn => createFnInfoVarNode(childFn.id, state))),
                        state.getSourcesNode
                ]))
        ]));
}

overlookmotel / livepack / 6963313779

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