overlookmotel / livepack / 6908299522

/* --------------------

 * livepack module

 * Code instrumentation visitors for identifiers

 * ------------------*/

'use strict';

// Export

module.exports = {

        IdentifierReadOnly,

        IdentifierAssignOnly,

        IdentifierReadAndAssign,

        ThisExpression,

        NewTargetExpression

};

// Imports

const visitEval = require('./eval.js'),

        {getOrCreateExternalVar, activateBlock, activateBinding, createInternalVar} = require('../blocks.js'),

        {checkInternalVarNameClash} = require('../internalVars.js'),

        {

                CONST_VIOLATION_CONST, CONST_VIOLATION_FUNCTION_THROWING, CONST_VIOLATION_FUNCTION_SILENT

        } = require('../../shared/constants.js');

// Exports

/**

 * Visitor for identifier where only read from e.g. `x + 1`.

 * @param {Object} node - 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 IdentifierReadOnly(node, state, parent, key) {

        const varName = node.name;

        visitIdentifier(node, varName, true, false, state);

        // Handle `eval`

        if (varName === 'eval') visitEval(node, parent, key, state);

}

/**

 * Visitor for identifier where only assigned to e.g. `x = 1`.

 * @param {Object} node - AST node

 * @param {Object} state - State object

 * @returns {undefined}

 */

function IdentifierAssignOnly(node, state) {

        visitIdentifier(node, node.name, false, true, state);

 * Visitor for identifier where both read from and assigned to e.g. `x += 2`.

 * @param {Object} node - AST node

 * @param {Object} state - State object

function IdentifierReadAndAssign(node, state) {

        visitIdentifier(node, node.name, true, true, state);

}

/**

 * Visitor for `this` expression.

 * Record use immediately. No need to wait until 2nd pass as no ambiguity as to where `this` is bound.

 * @param {Object} node - AST node

 * @param {Object} state - State object

 * @returns {undefined}

 */

function ThisExpression(node, state) {

        const fn = state.currentFunction;

        if (!fn) return;

        // Ignore if `this` is global

        const block = state.currentThisBlock,

                binding = block.bindings.this;

        if (!binding) return;

        // Record as internal/external var use in function.

        // Ignore if internal to function, unless in class constructor or prototype class property

        // of class with super class.

        if (block.id < fn.id) {

                recordExternalVar(binding, block, 'this', fn, [...state.trail], true, false, state);

        } else if (fn.hasSuperClass) {

                createInternalVar(fn, 'this', binding, [...state.trail]);

        }

}

/**

 * Visitor for `new.target` expression.

 * Record use immediately. No need to wait until 2nd pass as no ambiguity as to where it's bound.

 * @param {Object} node - AST node

 * @param {Object} state - State object

 * @returns {undefined}

 */

function NewTargetExpression(node, state) {

        // `new.target` can appear outside functions in CommonJS code.

        const fn = state.currentFunction;

        if (!fn) return;

        // Record as external var use in function.

        // NB: No need to check if binding exists, because if it doesn't,

        // parser will have already rejected the code as syntax error.

        const block = state.currentThisBlock;

        if (block.id < fn.id) {

                        block.bindings['new.target'], block, 'new.target', fn, [...state.trail], true, false, state

                );

        }

}

/**

 * Visit identifier.

 * @param {Object} node - Identifier AST node

 * @param {string} varName - Var name

 * @param {boolean} isReadFrom - `true` if variable is read from e.g. `x + 1`, `x++`

 * @param {boolean} isAssignedTo - `true` if variable is assigned to e.g. `x = 1`, `x++`

 * @param {Object} state - State object

 * @returns {undefined}

 */

function visitIdentifier(node, varName, isReadFrom, isAssignedTo, state) {

 * @param {Object} block - Block object

 * @param {string} varName - Variable name

 * @param {Object} fn - Function object

 * @param {Array<string|number>} trail - Trail

 * @param {boolean} isReadFrom - `true` if variable is read from

 * @param {boolean} isAssignedTo - `true` if variable is assigned to

 * @param {boolean} isStrict - `true` if variable used in strict mode

 * @param {Object} state - State object

 * @returns {undefined}

 */

function resolveIdentifier(node, block, varName, fn, trail, isReadFrom, isAssignedTo, isStrict, state) {

        // Find binding

        let binding;

        do {

                binding = block.bindings[varName];

        } while (!binding && (block = block.parent)); // eslint-disable-line no-cond-assign

        // Record if global var

        if (!binding) {

                // Vars which are local bindings have var name checked for internal var name clashes

                // when the binding is created. But here there's no binding, so need to do the check.

                checkInternalVarNameClash(varName, state);

                fn.globalVarNames.add(varName);

                return;

        }

        // Record if internal var

        if (block.id >= fn.id) {

                if (!binding.isFunction && !binding.argNames) fn.internalVars.get(binding).trails.push(trail);

                return;

        }

        // Record external var

        if (isAssignedTo && binding.isConst) {

                // Record const violation

                fn.amendments.push({

                        type: binding.isSilentConst && !isStrict

                                ? CONST_VIOLATION_FUNCTION_SILENT

                                : binding.isFunction

                                        ? CONST_VIOLATION_FUNCTION_THROWING

                                        : CONST_VIOLATION_CONST,

                        blockId: block.id,

                        trail

                });

                if (!isReadFrom) return;

                isAssignedTo = false;

        }

        recordExternalVar(binding, block, varName, fn, trail, isReadFrom, isAssignedTo, state);

}

/**

 * Record an external var's usage within a function.

 * @param {Object} binding - Binding object

 * @param {Object} block - Block object

 * @param {string} varName - Variable name

 * @param {Object} fn - Function object

 * @param {Array<string|number>} trail - Trail

 * @param {boolean} isReadFrom - `true` if variable is read from

 * @param {boolean} isAssignedTo - `true` if variable is assigned to

 * @param {Object} state - State object

 * @returns {undefined}

 */

function recordExternalVar(binding, block, varName, fn, trail, isReadFrom, isAssignedTo, state) {

        const externalVar = getOrCreateExternalVar(fn.externalVars, block, varName, binding);

        if (isReadFrom) externalVar.isReadFrom = true;

        if (isAssignedTo) externalVar.isAssignedTo = true;

        externalVar.trails.push(trail);

}