source: frontend/node_modules/enhanced-resolve/lib/createInnerContext.js

/*
        MIT License http://www.opensource.org/licenses/mit-license.php
        Author Tobias Koppers @sokra
*/

"use strict";

/** @typedef {import("./Resolver").ResolveContext} ResolveContext */

/**
 * Build the `ResolveContext` passed into the next hook in the chain.
 *
 * The caller — `Resolver.doResolve` — runs on every resolve step, so we
 * want to allocate as little as possible here. Previously the caller
 * constructed a temporary `{ log, yield, fileDependencies, ... }` literal
 * and handed it to this helper, which then copied those same fields into
 * a second fresh object. That's two allocations per step for what is
 * effectively a struct copy with one mutated field (`stack`) and one
 * optionally-wrapped field (`log`). Taking the parent context and the
 * two things we actually want to change (stack, message) as separate
 * arguments lets us allocate exactly one inner context.
 * @param {ResolveContext} parent parent resolve context to inherit dependency sets / yield from
 * @param {ResolveContext["stack"]} stack new stack tip for the nested call
 * @param {null | string} message log message prefix for this step
 * @returns {ResolveContext} inner context
 */
module.exports = function createInnerContext(parent, stack, message) {
        const parentLog = parent.log;
        let innerLog;
        if (parentLog) {
                if (message) {
                        let messageReported = false;
                        /**
                         * @param {string} msg message
                         */
                        innerLog = (msg) => {
                                if (!messageReported) {
                                        parentLog(message);
                                        messageReported = true;
                                }
                                parentLog(`  ${msg}`);
                        };
                } else {
                        innerLog = parentLog;
                }
        }

        return {
                log: innerLog,
                yield: parent.yield,
                fileDependencies: parent.fileDependencies,
                contextDependencies: parent.contextDependencies,
                missingDependencies: parent.missingDependencies,
                stack,
        };
};