source: frontend/node_modules/webpack/lib/WarnCaseSensitiveModulesPlugin.js

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

"use strict";

/** @typedef {import("./Compiler")} Compiler */
/** @typedef {import("./Module")} Module */
/** @typedef {import("./ModuleGraph")} ModuleGraph */
/** @typedef {import("./NormalModule")} NormalModule */

const WebpackError = require("./errors/WebpackError");

/**
 * Sorts the conflicting modules by identifier to keep warning output stable.
 * @param {Module[]} modules the modules to be sorted
 * @returns {Module[]} sorted version of original modules
 */
const sortModules = (modules) =>
        modules.sort((a, b) => {
                const aIdent = a.identifier();
                const bIdent = b.identifier();
                /* istanbul ignore next */
                if (aIdent < bIdent) return -1;
                /* istanbul ignore next */
                if (aIdent > bIdent) return 1;
                /* istanbul ignore next */
                return 0;
        });

/**
 * Formats the conflicting modules and one representative incoming reason for
 * each module into the warning body.
 * @param {Module[]} modules each module from throw
 * @param {ModuleGraph} moduleGraph the module graph
 * @returns {string} each message from provided modules
 */
const createModulesListMessage = (modules, moduleGraph) =>
        modules
                .map((m) => {
                        let message = `* ${m.identifier()}`;
                        const validReasons = [
                                ...moduleGraph.getIncomingConnectionsByOriginModule(m).keys()
                        ].filter(Boolean);

                        if (validReasons.length > 0) {
                                message += `\n    Used by ${validReasons.length} module(s), i. e.`;
                                message += `\n    ${
                                        /** @type {Module[]} */ (validReasons)[0].identifier()
                                }`;
                        }
                        return message;
                })
                .join("\n");

/**
 * Warning emitted when webpack finds modules whose identifiers differ only by
 * letter casing, which can behave inconsistently across filesystems.
 */
class CaseSensitiveModulesWarning extends WebpackError {
        /**
         * Builds a warning message that lists the case-conflicting modules and
         * representative importers that caused them to be included.
         * @param {Iterable<Module>} modules modules that were detected
         * @param {ModuleGraph} moduleGraph the module graph
         */
        constructor(modules, moduleGraph) {
                const sortedModules = sortModules([...modules]);
                const modulesList = createModulesListMessage(sortedModules, moduleGraph);
                super(`There are multiple modules with names that only differ in casing.
This can lead to unexpected behavior when compiling on a filesystem with other case-semantic.
Use equal casing. Compare these module identifiers:
${modulesList}`);

                /** @type {string} */
                this.name = "CaseSensitiveModulesWarning";
                this.module = sortedModules[0];
        }
}

const PLUGIN_NAME = "WarnCaseSensitiveModulesPlugin";

class WarnCaseSensitiveModulesPlugin {
        /**
         * Applies the plugin by registering its hooks on the compiler.
         * @param {Compiler} compiler the compiler instance
         * @returns {void}
         */
        apply(compiler) {
                compiler.hooks.compilation.tap(PLUGIN_NAME, (compilation) => {
                        compilation.hooks.seal.tap(PLUGIN_NAME, () => {
                                /** @type {Map<string, Map<string, Module>>} */
                                const moduleWithoutCase = new Map();
                                for (const module of compilation.modules) {
                                        const identifier = module.identifier();

                                        // Ignore `data:` URLs, because it's not a real path
                                        if (
                                                /** @type {NormalModule} */
                                                (module).resourceResolveData !== undefined &&
                                                /** @type {NormalModule} */
                                                (module).resourceResolveData.encodedContent !== undefined
                                        ) {
                                                continue;
                                        }

                                        const lowerIdentifier = identifier.toLowerCase();
                                        let map = moduleWithoutCase.get(lowerIdentifier);
                                        if (map === undefined) {
                                                map = new Map();
                                                moduleWithoutCase.set(lowerIdentifier, map);
                                        }
                                        map.set(identifier, module);
                                }
                                for (const pair of moduleWithoutCase) {
                                        const map = pair[1];
                                        if (map.size > 1) {
                                                compilation.warnings.push(
                                                        new CaseSensitiveModulesWarning(
                                                                map.values(),
                                                                compilation.moduleGraph
                                                        )
                                                );
                                        }
                                }
                        });
                });
        }
}

module.exports = WarnCaseSensitiveModulesPlugin;