index.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import { BuilderContext, BuilderOutput, createBuilder } from '@angular-devkit/architect';
import { EmittedFiles, WebpackLoggingCallback, runWebpack } from '@angular-devkit/build-webpack';
import { join, json, logging, normalize, tags, virtualFs } from '@angular-devkit/core';
import { NodeJsSyncHost } from '@angular-devkit/core/node';
import * as fs from 'fs';
import * as path from 'path';
import { Observable, from } from 'rxjs';
import { concatMap, map, switchMap } from 'rxjs/operators';
import { ScriptTarget } from 'typescript';
import * as webpack from 'webpack';
import { NgBuildAnalyticsPlugin } from '../../plugins/webpack/analytics';
import { WebpackConfigOptions } from '../angular-cli-files/models/build-options';
import {
  getAotConfig,
  getBrowserConfig,
  getCommonConfig,
  getNonAotConfig,
  getStatsConfig,
  getStylesConfig,
  getWorkerConfig,
  normalizeExtraEntryPoints,
} from '../angular-cli-files/models/webpack-configs';
import { markAsyncChunksNonInitial } from '../angular-cli-files/utilities/async-chunks';
import { ThresholdSeverity, checkBudgets } from '../angular-cli-files/utilities/bundle-calculator';
import {
  IndexHtmlTransform,
  writeIndexHtml,
} from '../angular-cli-files/utilities/index-file/write-index-html';
import { readTsconfig } from '../angular-cli-files/utilities/read-tsconfig';
import { augmentAppWithServiceWorker } from '../angular-cli-files/utilities/service-worker';
import {
  generateBuildStats,
  generateBundleStats,
  statsErrorsToString,
  statsToString,
  statsWarningsToString,
} from '../angular-cli-files/utilities/stats';
import { ExecutionTransformer } from '../transforms';
import {
  BuildBrowserFeatures,
  deleteOutputDir,
  normalizeAssetPatterns,
  normalizeOptimization,
  normalizeSourceMaps,
  urlJoin,
} from '../utils';
import { BundleActionExecutor } from '../utils/action-executor';
import { findCachePath } from '../utils/cache-path';
import { copyAssets } from '../utils/copy-assets';
import { cachingDisabled } from '../utils/environment-options';
import { i18nInlineEmittedFiles } from '../utils/i18n-inlining';
import { I18nOptions } from '../utils/i18n-options';
import { ensureOutputPaths } from '../utils/output-paths';
import {
  InlineOptions,
  ProcessBundleFile,
  ProcessBundleOptions,
  ProcessBundleResult,
} from '../utils/process-bundle';
import { assertCompatibleAngularVersion } from '../utils/version';
import {
  BrowserWebpackConfigOptions,
  generateBrowserWebpackConfigFromContext,
  generateI18nBrowserWebpackConfigFromContext,
  getIndexInputFile,
  getIndexOutputFile,
} from '../utils/webpack-browser-config';
import { Schema as BrowserBuilderSchema } from './schema';

const cacheDownlevelPath = cachingDisabled ? undefined : findCachePath('angular-build-dl');

export type BrowserBuilderOutput = json.JsonObject &
  BuilderOutput & {
    baseOutputPath: string;
    outputPaths: string[];
    /**
     * @deprecated in version 9. Use 'outputPaths' instead.
     */
    outputPath: string;
  };

export function createBrowserLoggingCallback(
  verbose: boolean,
  logger: logging.LoggerApi,
): WebpackLoggingCallback {
  return (stats, config) => {
    // config.stats contains our own stats settings, added during buildWebpackConfig().
    const json = stats.toJson(config.stats);
    if (verbose) {
      logger.info(stats.toString(config.stats));
    } else {
      logger.info(statsToString(json, config.stats));
    }

    if (stats.hasWarnings()) {
      logger.warn(statsWarningsToString(json, config.stats));
    }
    if (stats.hasErrors()) {
      logger.error(statsErrorsToString(json, config.stats));
    }
  };
}

// todo: the below should be cleaned once dev-server support the new i18n
interface ConfigFromContextReturn {
  config: webpack.Configuration;
  projectRoot: string;
  projectSourceRoot?: string;
}

export async function buildBrowserWebpackConfigFromContext(
  options: BrowserBuilderSchema,
  context: BuilderContext,
  host: virtualFs.Host<fs.Stats>,
  i18n: boolean,
): Promise<ConfigFromContextReturn & { i18n: I18nOptions }>;
export async function buildBrowserWebpackConfigFromContext(
  options: BrowserBuilderSchema,
  context: BuilderContext,
  host?: virtualFs.Host<fs.Stats>,
): Promise<ConfigFromContextReturn>;
export async function buildBrowserWebpackConfigFromContext(
  options: BrowserBuilderSchema,
  context: BuilderContext,
  host: virtualFs.Host<fs.Stats> = new NodeJsSyncHost(),
  i18n = false,
): Promise<ConfigFromContextReturn & { i18n?: I18nOptions }> {
  const webpackPartialGenerator = (wco: BrowserWebpackConfigOptions) => [
    getCommonConfig(wco),
    getBrowserConfig(wco),
    getStylesConfig(wco),
    getStatsConfig(wco),
    getAnalyticsConfig(wco, context),
    getCompilerConfig(wco),
    wco.buildOptions.webWorkerTsConfig ? getWorkerConfig(wco) : {},
  ];

  if (i18n) {
    return generateI18nBrowserWebpackConfigFromContext(
      options,
      context,
      webpackPartialGenerator,
      host,
    );
  }

  return generateBrowserWebpackConfigFromContext(options, context, webpackPartialGenerator, host);
}

function getAnalyticsConfig(
  wco: WebpackConfigOptions,
  context: BuilderContext,
): webpack.Configuration {
  if (context.analytics) {
    // If there's analytics, add our plugin. Otherwise no need to slow down the build.
    let category = 'build';
    if (context.builder) {
      // We already vetted that this is a "safe" package, otherwise the analytics would be noop.
      category =
        context.builder.builderName.split(':')[1] || context.builder.builderName || 'build';
    }

    // The category is the builder name if it's an angular builder.
    return {
      plugins: [new NgBuildAnalyticsPlugin(
        wco.projectRoot,
        context.analytics,
        category,
        !!wco.tsConfig.options.enableIvy,
      )],
    };
  }

  return {};
}

function getCompilerConfig(wco: WebpackConfigOptions): webpack.Configuration {
  if (wco.buildOptions.main || wco.buildOptions.polyfills) {
    return wco.buildOptions.aot ? getAotConfig(wco) : getNonAotConfig(wco);
  }

  return {};
}

async function initialize(
  options: BrowserBuilderSchema,
  context: BuilderContext,
  host: virtualFs.Host<fs.Stats>,
  webpackConfigurationTransform?: ExecutionTransformer<webpack.Configuration>,
): Promise<{
  config: webpack.Configuration;
  projectRoot: string;
  projectSourceRoot?: string;
  i18n: I18nOptions;
}> {
  const originalOutputPath = options.outputPath;
  const {
    config,
    projectRoot,
    projectSourceRoot,
    i18n,
  } = await buildBrowserWebpackConfigFromContext(options, context, host, true);

  let transformedConfig;
  if (webpackConfigurationTransform) {
    transformedConfig = await webpackConfigurationTransform(config);
  }

  if (options.deleteOutputPath) {
    deleteOutputDir(context.workspaceRoot, originalOutputPath);
  }

  return { config: transformedConfig || config, projectRoot, projectSourceRoot, i18n };
}

// tslint:disable-next-line: no-big-function
export function buildWebpackBrowser(
  options: BrowserBuilderSchema,
  context: BuilderContext,
  transforms: {
    webpackConfiguration?: ExecutionTransformer<webpack.Configuration>;
    logging?: WebpackLoggingCallback;
    indexHtml?: IndexHtmlTransform;
  } = {},
): Observable<BrowserBuilderOutput> {
  const host = new NodeJsSyncHost();
  const root = normalize(context.workspaceRoot);
  const baseOutputPath = path.resolve(context.workspaceRoot, options.outputPath);
  let outputPaths: undefined | Map<string, string>;

  // Check Angular version.
  assertCompatibleAngularVersion(context.workspaceRoot, context.logger);

  return from(initialize(options, context, host, transforms.webpackConfiguration)).pipe(
    // tslint:disable-next-line: no-big-function
    switchMap(({ config, projectRoot, projectSourceRoot, i18n }) => {
      const tsConfig = readTsconfig(options.tsConfig, context.workspaceRoot);
      const target = tsConfig.options.target || ScriptTarget.ES5;
      const buildBrowserFeatures = new BuildBrowserFeatures(projectRoot, target);
      const isDifferentialLoadingNeeded = buildBrowserFeatures.isDifferentialLoadingNeeded();

      if (target > ScriptTarget.ES2015 && isDifferentialLoadingNeeded) {
        context.logger.warn(tags.stripIndent`
          WARNING: Using differential loading with targets ES5 and ES2016 or higher may
          cause problems. Browsers with support for ES2015 will load the ES2016+ scripts
          referenced with script[type="module"] but they may not support ES2016+ syntax.
        `);
      }

      const useBundleDownleveling = isDifferentialLoadingNeeded && !options.watch;
      const startTime = Date.now();

      return runWebpack(config, context, {
        webpackFactory: require('webpack') as typeof webpack,
        logging:
          transforms.logging ||
          (useBundleDownleveling
            ? () => {}
            : createBrowserLoggingCallback(!!options.verbose, context.logger)),
      }).pipe(
        // tslint:disable-next-line: no-big-function
        concatMap(async buildEvent => {
          const { webpackStats: webpackRawStats, success, emittedFiles = [] } = buildEvent;
          if (!webpackRawStats) {
            throw new Error('Webpack stats build result is required.');
          }

          // Fix incorrectly set `initial` value on chunks.
          const extraEntryPoints = normalizeExtraEntryPoints(options.styles || [], 'styles')
              .concat(normalizeExtraEntryPoints(options.scripts || [], 'scripts'));
          const webpackStats = {
            ...webpackRawStats,
            chunks: markAsyncChunksNonInitial(webpackRawStats, extraEntryPoints),
          };

          if (!success && useBundleDownleveling) {
            // If using bundle downleveling then there is only one build
            // If it fails show any diagnostic messages and bail
            if (webpackStats && webpackStats.warnings.length > 0) {
              context.logger.warn(statsWarningsToString(webpackStats, { colors: true }));
            }
            if (webpackStats && webpackStats.errors.length > 0) {
              context.logger.error(statsErrorsToString(webpackStats, { colors: true }));
            }

            return { success };
          } else if (success) {
            outputPaths = ensureOutputPaths(baseOutputPath, i18n);

            let noModuleFiles: EmittedFiles[] | undefined;
            let moduleFiles: EmittedFiles[] | undefined;
            let files: EmittedFiles[] | undefined;

            const scriptsEntryPointName = normalizeExtraEntryPoints(
              options.scripts || [],
              'scripts',
            ).map(x => x.bundleName);

            if (isDifferentialLoadingNeeded && options.watch) {
              moduleFiles = emittedFiles;
              files = moduleFiles.filter(
                x => x.extension === '.css' || (x.name && scriptsEntryPointName.includes(x.name)),
              );
              if (i18n.shouldInline) {
                const success = await i18nInlineEmittedFiles(
                  context,
                  emittedFiles,
                  i18n,
                  baseOutputPath,
                  Array.from(outputPaths.values()),
                  scriptsEntryPointName,
                  // tslint:disable-next-line: no-non-null-assertion
                  webpackStats.outputPath!,
                  target <= ScriptTarget.ES5,
                  options.i18nMissingTranslation,
                );
                if (!success) {
                  return { success: false };
                }
              }
            } else if (isDifferentialLoadingNeeded) {
              moduleFiles = [];
              noModuleFiles = [];

              // Common options for all bundle process actions
              const sourceMapOptions = normalizeSourceMaps(options.sourceMap || false);
              const actionOptions: Partial<ProcessBundleOptions> = {
                optimize: normalizeOptimization(options.optimization).scripts,
                sourceMaps: sourceMapOptions.scripts,
                hiddenSourceMaps: sourceMapOptions.hidden,
                vendorSourceMaps: sourceMapOptions.vendor,
                integrityAlgorithm: options.subresourceIntegrity ? 'sha384' : undefined,
              };

              let mainChunkId;
              const actions: ProcessBundleOptions[] = [];
              let workerReplacements: [string, string][] | undefined;
              const seen = new Set<string>();
              for (const file of emittedFiles) {
                // Assets are not processed nor injected into the index
                if (file.asset) {
                  // WorkerPlugin adds worker files to assets
                  if (file.file.endsWith('.worker.js')) {
                    if (!workerReplacements) {
                      workerReplacements = [];
                    }
                    workerReplacements.push([
                      file.file,
                      file.file.replace(/\-(es20\d{2}|esnext)/, '-es5'),
                    ]);
                  } else {
                    continue;
                  }
                }

                // Scripts and non-javascript files are not processed
                if (
                  file.extension !== '.js' ||
                  (file.name && scriptsEntryPointName.includes(file.name))
                ) {
                  if (files === undefined) {
                    files = [];
                  }
                  files.push(file);
                  continue;
                }

                // Ignore already processed files; emittedFiles can contain duplicates
                if (seen.has(file.file)) {
                  continue;
                }
                seen.add(file.file);

                if (file.name === 'vendor' || (!mainChunkId && file.name === 'main')) {
                  // tslint:disable-next-line: no-non-null-assertion
                  mainChunkId = file.id!.toString();
                }

                // All files at this point except ES5 polyfills are module scripts
                const es5Polyfills = file.file.startsWith('polyfills-es5');
                if (!es5Polyfills) {
                  moduleFiles.push(file);
                }

                // Retrieve the content/map for the file
                // NOTE: Additional future optimizations will read directly from memory
                // tslint:disable-next-line: no-non-null-assertion
                let filename = path.join(webpackStats.outputPath!, file.file);
                const code = fs.readFileSync(filename, 'utf8');
                let map;
                if (actionOptions.sourceMaps) {
                  try {
                    map = fs.readFileSync(filename + '.map', 'utf8');
                    if (es5Polyfills) {
                      fs.unlinkSync(filename + '.map');
                    }
                  } catch {}
                }

                if (es5Polyfills) {
                  fs.unlinkSync(filename);
                  filename = filename.replace(/\-es20\d{2}/, '');
                }

                const es2015Polyfills = file.file.startsWith('polyfills-es20');

                // Record the bundle processing action
                // The runtime chunk gets special processing for lazy loaded files
                actions.push({
                  ...actionOptions,
                  filename,
                  code,
                  map,
                  // id is always present for non-assets
                  // tslint:disable-next-line: no-non-null-assertion
                  name: file.id!,
                  runtime: file.file.startsWith('runtime'),
                  ignoreOriginal: es5Polyfills,
                  optimizeOnly: es2015Polyfills,
                });

                // ES2015 polyfills are only optimized; optimization check was performed above
                if (es2015Polyfills) {
                  continue;
                }

                // Add the newly created ES5 bundles to the index as nomodule scripts
                const newFilename = es5Polyfills
                  ? file.file.replace(/\-es20\d{2}/, '')
                  : file.file.replace(/\-(es20\d{2}|esnext)/, '-es5');
                noModuleFiles.push({ ...file, file: newFilename });
              }

              const processActions: typeof actions = [];
              let processRuntimeAction: ProcessBundleOptions | undefined;
              const processResults: ProcessBundleResult[] = [];
              for (const action of actions) {
                // If SRI is enabled always process the runtime bundle
                // Lazy route integrity values are stored in the runtime bundle
                if (action.integrityAlgorithm && action.runtime) {
                  processRuntimeAction = action;
                } else {
                  processActions.push({ replacements: workerReplacements, ...action });
                }
              }

              const executor = new BundleActionExecutor(
                { cachePath: cacheDownlevelPath, i18n },
                options.subresourceIntegrity ? 'sha384' : undefined,
              );

              // Execute the bundle processing actions
              try {
                context.logger.info('Generating ES5 bundles for differential loading...');

                for await (const result of executor.processAll(processActions)) {
                  processResults.push(result);
                }

                // Runtime must be processed after all other files
                if (processRuntimeAction) {
                  const runtimeOptions = {
                    ...processRuntimeAction,
                    runtimeData: processResults,
                    supportedBrowsers: buildBrowserFeatures.supportedBrowsers,
                  };
                  processResults.push(
                    await import('../utils/process-bundle').then(m => m.process(runtimeOptions)),
                  );
                }

                context.logger.info('ES5 bundle generation complete.');

                if (i18n.shouldInline) {
                  context.logger.info('Generating localized bundles...');

                  const inlineActions: InlineOptions[] = [];
                  const processedFiles = new Set<string>();
                  for (const result of processResults) {
                    if (result.original) {
                      inlineActions.push({
                        filename: path.basename(result.original.filename),
                        code: fs.readFileSync(result.original.filename, 'utf8'),
                        map:
                          result.original.map &&
                          fs.readFileSync(result.original.map.filename, 'utf8'),
                        outputPath: baseOutputPath,
                        es5: false,
                        missingTranslation: options.i18nMissingTranslation,
                        setLocale: result.name === mainChunkId,
                      });
                      processedFiles.add(result.original.filename);
                      if (result.original.map) {
                        processedFiles.add(result.original.map.filename);
                      }
                    }
                    if (result.downlevel) {
                      inlineActions.push({
                        filename: path.basename(result.downlevel.filename),
                        code: fs.readFileSync(result.downlevel.filename, 'utf8'),
                        map:
                          result.downlevel.map &&
                          fs.readFileSync(result.downlevel.map.filename, 'utf8'),
                        outputPath: baseOutputPath,
                        es5: true,
                        missingTranslation: options.i18nMissingTranslation,
                        setLocale: result.name === mainChunkId,
                      });
                      processedFiles.add(result.downlevel.filename);
                      if (result.downlevel.map) {
                        processedFiles.add(result.downlevel.map.filename);
                      }
                    }
                  }

                  let hasErrors = false;
                  try {
                    for await (const result of executor.inlineAll(inlineActions)) {
                      if (options.verbose) {
                        context.logger.info(
                          `Localized "${result.file}" [${result.count} translation(s)].`,
                        );
                      }
                      for (const diagnostic of result.diagnostics) {
                        if (diagnostic.type === 'error') {
                          hasErrors = true;
                          context.logger.error(diagnostic.message);
                        } else {
                          context.logger.warn(diagnostic.message);
                        }
                      }
                    }

                    // Copy any non-processed files into the output locations
                    await copyAssets(
                      [
                        {
                          glob: '**/*',
                          // tslint:disable-next-line: no-non-null-assertion
                          input: webpackStats.outputPath!,
                          output: '',
                          ignore: [...processedFiles].map(f =>
                            // tslint:disable-next-line: no-non-null-assertion
                            path.relative(webpackStats.outputPath!, f),
                          ),
                        },
                      ],
                      Array.from(outputPaths.values()),
                      '',
                    );
                  } catch (err) {
                    context.logger.error('Localized bundle generation failed: ' + err.message);

                    return { success: false };
                  }

                  context.logger.info(
                    `Localized bundle generation ${hasErrors ? 'failed' : 'complete'}.`,
                  );

                  if (hasErrors) {
                    return { success: false };
                  }
                }
              } finally {
                await executor.stop();
              }

              // Copy assets
              if (options.assets) {
                try {
                  await copyAssets(
                    normalizeAssetPatterns(
                      options.assets,
                      new virtualFs.SyncDelegateHost(host),
                      root,
                      normalize(projectRoot),
                      projectSourceRoot === undefined ? undefined : normalize(projectSourceRoot),
                    ),
                    Array.from(outputPaths.values()),
                    context.workspaceRoot,
                  );
                } catch (err) {
                  context.logger.error('Unable to copy assets: ' + err.message);

                  return { success: false };
                }
              }

              type ArrayElement<A> = A extends ReadonlyArray<infer T> ? T : never;
              function generateBundleInfoStats(
                id: string | number,
                bundle: ProcessBundleFile,
                chunk: ArrayElement<webpack.Stats.ToJsonOutput['chunks']> | undefined,
              ): string {
                return generateBundleStats(
                  {
                    id,
                    size: bundle.size,
                    files: bundle.map ? [bundle.filename, bundle.map.filename] : [bundle.filename],
                    names: chunk && chunk.names,
                    entry: !!chunk && chunk.names.includes('runtime'),
                    initial: !!chunk && chunk.initial,
                    rendered: true,
                  },
                  true,
                );
              }

              let bundleInfoText = '';
              for (const result of processResults) {
                const chunk = webpackStats.chunks
                    && webpackStats.chunks.find((chunk) => chunk.id.toString() === result.name);

                if (result.original) {
                  bundleInfoText +=
                    '\n' + generateBundleInfoStats(result.name, result.original, chunk);
                }

                if (result.downlevel) {
                  bundleInfoText +=
                    '\n' + generateBundleInfoStats(result.name, result.downlevel, chunk);
                }
              }

              const unprocessedChunks = webpackStats.chunks && webpackStats.chunks
                  .filter((chunk) => !processResults
                      .find((result) => chunk.id.toString() === result.name),
                  ) || [];
              for (const chunk of unprocessedChunks) {
                const asset =
                    webpackStats.assets && webpackStats.assets.find(a => a.name === chunk.files[0]);
                bundleInfoText +=
                  '\n' + generateBundleStats({ ...chunk, size: asset && asset.size }, true);
              }

              bundleInfoText +=
                '\n' +
                generateBuildStats(
                  (webpackStats && webpackStats.hash) || '<unknown>',
                  Date.now() - startTime,
                  true,
                );
              context.logger.info(bundleInfoText);

              // Check for budget errors and display them to the user.
              const budgets = options.budgets || [];
              const budgetFailures = checkBudgets(budgets, webpackStats, processResults);
              for (const {severity, message} of budgetFailures) {
                const msg = `budgets: ${message}`;
                switch (severity) {
                  case ThresholdSeverity.Warning:
                    webpackStats.warnings.push(msg);
                    break;
                  case ThresholdSeverity.Error:
                    webpackStats.errors.push(msg);
                    break;
                  default:
                    assertNever(severity);
                    break;
                }
              }

              if (webpackStats && webpackStats.warnings.length > 0) {
                context.logger.warn(statsWarningsToString(webpackStats, { colors: true }));
              }
              if (webpackStats && webpackStats.errors.length > 0) {
                context.logger.error(statsErrorsToString(webpackStats, { colors: true }));

                return { success: false };
              }
            } else {
              files = emittedFiles.filter(x => x.name !== 'polyfills-es5');
              noModuleFiles = emittedFiles.filter(x => x.name === 'polyfills-es5');
              if (i18n.shouldInline) {
                const success = await i18nInlineEmittedFiles(
                  context,
                  emittedFiles,
                  i18n,
                  baseOutputPath,
                  Array.from(outputPaths.values()),
                  scriptsEntryPointName,
                  // tslint:disable-next-line: no-non-null-assertion
                  webpackStats.outputPath!,
                  target <= ScriptTarget.ES5,
                  options.i18nMissingTranslation,
                );
                if (!success) {
                  return { success: false };
                }
              }
            }

            if (options.index) {
              for (const [locale, outputPath] of outputPaths.entries()) {
                let localeBaseHref;
                if (i18n.locales[locale] && i18n.locales[locale].baseHref !== '') {
                  localeBaseHref = urlJoin(
                    options.baseHref || '',
                    i18n.locales[locale].baseHref ?? `/${locale}/`,
                  );
                }

                try {
                  await generateIndex(
                    outputPath,
                    options,
                    root,
                    files,
                    noModuleFiles,
                    moduleFiles,
                    transforms.indexHtml,
                    // i18nLocale is used when Ivy is disabled
                    locale || options.i18nLocale,
                    localeBaseHref || options.baseHref,
                  );
                } catch (err) {
                  return { success: false, error: mapErrorToMessage(err) };
                }
              }
            }

            if (!options.watch && options.serviceWorker) {
              for (const [locale, outputPath] of outputPaths.entries()) {
                let localeBaseHref;
                if (i18n.locales[locale] && i18n.locales[locale].baseHref !== '') {
                  localeBaseHref = urlJoin(
                    options.baseHref || '',
                    i18n.locales[locale].baseHref ?? `/${locale}/`,
                  );
                }

                try {
                  await augmentAppWithServiceWorker(
                    host,
                    root,
                    normalize(projectRoot),
                    normalize(outputPath),
                    localeBaseHref || options.baseHref || '/',
                    options.ngswConfigPath,
                  );
                } catch (err) {
                  return { success: false, error: mapErrorToMessage(err) };
                }
              }
            }
          }

          return { success };
        }),
        map(
          event =>
            ({
              ...event,
              baseOutputPath,
              outputPath: baseOutputPath,
              outputPaths: outputPaths && Array.from(outputPaths.values()) || [baseOutputPath],
            } as BrowserBuilderOutput),
        ),
      );
    }),
  );
}

function generateIndex(
  baseOutputPath: string,
  options: BrowserBuilderSchema,
  root: string,
  files: EmittedFiles[] | undefined,
  noModuleFiles: EmittedFiles[] | undefined,
  moduleFiles: EmittedFiles[] | undefined,
  transformer?: IndexHtmlTransform,
  locale?: string,
  baseHref?: string,
): Promise<void> {
  const host = new NodeJsSyncHost();

  return writeIndexHtml({
    host,
    outputPath: join(normalize(baseOutputPath), getIndexOutputFile(options)),
    indexPath: join(normalize(root), getIndexInputFile(options)),
    files,
    noModuleFiles,
    moduleFiles,
    baseHref,
    deployUrl: options.deployUrl,
    sri: options.subresourceIntegrity,
    scripts: options.scripts,
    styles: options.styles,
    postTransform: transformer,
    crossOrigin: options.crossOrigin,
    lang: locale,
  }).toPromise();
}

function mapErrorToMessage(error: unknown): string | undefined {
  if (error instanceof Error) {
    return error.message;
  }

  if (typeof error === 'string') {
    return error;
  }

  return undefined;
}

function assertNever(input: never): never {
  throw new Error(`Unexpected call to assertNever() with input: ${
      JSON.stringify(input, null /* replacer */, 4 /* tabSize */)}`);
}

export default createBuilder<json.JsonObject & BrowserBuilderSchema>(buildWebpackBrowser);