source: frontend/node_modules/webpack/lib/runtime/EnsureChunkRuntimeModule.js

/*
        MIT License http://www.opensource.org/licenses/mit-license.php
*/

"use strict";

const RuntimeGlobals = require("../RuntimeGlobals");
const RuntimeModule = require("../RuntimeModule");
const Template = require("../Template");

/** @typedef {import("../Compilation")} Compilation */
/** @typedef {import("../Module").ReadOnlyRuntimeRequirements} ReadOnlyRuntimeRequirements */

class EnsureChunkRuntimeModule extends RuntimeModule {
        /**
         * @param {ReadOnlyRuntimeRequirements} runtimeRequirements runtime requirements
         */
        constructor(runtimeRequirements) {
                super("ensure chunk");
                /** @type {ReadOnlyRuntimeRequirements} */
                this.runtimeRequirements = runtimeRequirements;
        }

        /**
         * Generates runtime code for this runtime module.
         * @returns {string | null} runtime code
         */
        generate() {
                const compilation = /** @type {Compilation} */ (this.compilation);
                const { runtimeTemplate } = compilation;
                // Check if there are non initial chunks which need to be imported using require-ensure
                if (this.runtimeRequirements.has(RuntimeGlobals.ensureChunkHandlers)) {
                        const withFetchPriority = this.runtimeRequirements.has(
                                RuntimeGlobals.hasFetchPriority
                        );
                        const handlers = RuntimeGlobals.ensureChunkHandlers;
                        return Template.asString([
                                `${handlers} = {};`,
                                "// This file contains only the entry chunk.",
                                "// The chunk loading function for additional chunks",
                                `${RuntimeGlobals.ensureChunk} = ${runtimeTemplate.basicFunction(
                                        `chunkId${withFetchPriority ? ", fetchPriority" : ""}`,
                                        [
                                                `return Promise.all(Object.keys(${handlers}).reduce(${runtimeTemplate.basicFunction(
                                                        "promises, key",
                                                        [
                                                                `${handlers}[key](chunkId, promises${
                                                                        withFetchPriority ? ", fetchPriority" : ""
                                                                });`,
                                                                "return promises;"
                                                        ]
                                                )}, []));`
                                        ]
                                )};`
                        ]);
                }
                // There ensureChunk is used somewhere in the tree, so we need an empty requireEnsure
                // function. This can happen with multiple entrypoints.
                return Template.asString([
                        "// The chunk loading function for additional chunks",
                        "// Since all referenced chunks are already included",
                        "// in this file, this function is empty here.",
                        `${RuntimeGlobals.ensureChunk} = ${runtimeTemplate.returningFunction(
                                "Promise.resolve()"
                        )};`
                ]);
        }
}

module.exports = EnsureChunkRuntimeModule;