index.js 25.7 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729
'use strict';

// use Polyfill for util.promisify in node versions < v8
const promisify = require('util.promisify');

const vm = require('vm');
const fs = require('fs');
const _ = require('lodash');
const path = require('path');
const childCompiler = require('./lib/compiler.js');
const prettyError = require('./lib/errors.js');
const chunkSorter = require('./lib/chunksorter.js');

const fsStatAsync = promisify(fs.stat);
const fsReadFileAsync = promisify(fs.readFile);

class HtmlWebpackPlugin {
  constructor (options) {
    // Default options
    this.options = _.extend({
      template: path.join(__dirname, 'default_index.ejs'),
      templateParameters: templateParametersGenerator,
      filename: 'index.html',
      hash: false,
      inject: true,
      compile: true,
      favicon: false,
      minify: false,
      cache: true,
      showErrors: true,
      chunks: 'all',
      excludeChunks: [],
      chunksSortMode: 'auto',
      meta: {},
      title: 'Webpack App',
      xhtml: false
    }, options);
  }

  apply (compiler) {
    const self = this;
    let isCompilationCached = false;
    let compilationPromise;

    this.options.template = this.getFullTemplatePath(this.options.template, compiler.context);

    // convert absolute filename into relative so that webpack can
    // generate it at correct location
    const filename = this.options.filename;
    if (path.resolve(filename) === path.normalize(filename)) {
      this.options.filename = path.relative(compiler.options.output.path, filename);
    }

    // setup hooks for webpack 4
    if (compiler.hooks) {
      compiler.hooks.compilation.tap('HtmlWebpackPluginHooks', compilation => {
        const SyncWaterfallHook = require('tapable').SyncWaterfallHook;
        const AsyncSeriesWaterfallHook = require('tapable').AsyncSeriesWaterfallHook;
        compilation.hooks.htmlWebpackPluginAlterChunks = new SyncWaterfallHook(['chunks', 'objectWithPluginRef']);
        compilation.hooks.htmlWebpackPluginBeforeHtmlGeneration = new AsyncSeriesWaterfallHook(['pluginArgs']);
        compilation.hooks.htmlWebpackPluginBeforeHtmlProcessing = new AsyncSeriesWaterfallHook(['pluginArgs']);
        compilation.hooks.htmlWebpackPluginAlterAssetTags = new AsyncSeriesWaterfallHook(['pluginArgs']);
        compilation.hooks.htmlWebpackPluginAfterHtmlProcessing = new AsyncSeriesWaterfallHook(['pluginArgs']);
        compilation.hooks.htmlWebpackPluginAfterEmit = new AsyncSeriesWaterfallHook(['pluginArgs']);
      });
    }

    // Backwards compatible version of: compiler.hooks.make.tapAsync()
    (compiler.hooks ? compiler.hooks.make.tapAsync.bind(compiler.hooks.make, 'HtmlWebpackPlugin') : compiler.plugin.bind(compiler, 'make'))((compilation, callback) => {
      // Compile the template (queued)
      compilationPromise = childCompiler.compileTemplate(self.options.template, compiler.context, self.options.filename, compilation)
        .catch(err => {
          compilation.errors.push(prettyError(err, compiler.context).toString());
          return {
            content: self.options.showErrors ? prettyError(err, compiler.context).toJsonHtml() : 'ERROR',
            outputName: self.options.filename
          };
        })
        .then(compilationResult => {
          // If the compilation change didnt change the cache is valid
          isCompilationCached = compilationResult.hash && self.childCompilerHash === compilationResult.hash;
          self.childCompilerHash = compilationResult.hash;
          self.childCompilationOutputName = compilationResult.outputName;
          callback();
          return compilationResult.content;
        });
    });

    // Backwards compatible version of: compiler.plugin.emit.tapAsync()
    (compiler.hooks ? compiler.hooks.emit.tapAsync.bind(compiler.hooks.emit, 'HtmlWebpackPlugin') : compiler.plugin.bind(compiler, 'emit'))((compilation, callback) => {
      const applyPluginsAsyncWaterfall = self.applyPluginsAsyncWaterfall(compilation);
      // Get chunks info as json
      // Note: we're excluding stuff that we don't need to improve toJson serialization speed.
      const chunkOnlyConfig = {
        assets: false,
        cached: false,
        children: false,
        chunks: true,
        chunkModules: false,
        chunkOrigins: false,
        errorDetails: false,
        hash: false,
        modules: false,
        reasons: false,
        source: false,
        timings: false,
        version: false
      };
      const allChunks = compilation.getStats().toJson(chunkOnlyConfig).chunks;
      // Filter chunks (options.chunks and options.excludeCHunks)
      let chunks = self.filterChunks(allChunks, self.options.chunks, self.options.excludeChunks);
      // Sort chunks
      chunks = self.sortChunks(chunks, self.options.chunksSortMode, compilation);
      // Let plugins alter the chunks and the chunk sorting
      if (compilation.hooks) {
        chunks = compilation.hooks.htmlWebpackPluginAlterChunks.call(chunks, { plugin: self });
      } else {
        // Before Webpack 4
        chunks = compilation.applyPluginsWaterfall('html-webpack-plugin-alter-chunks', chunks, { plugin: self });
      }
      // Get assets
      const assets = self.htmlWebpackPluginAssets(compilation, chunks);
      // If this is a hot update compilation, move on!
      // This solves a problem where an `index.html` file is generated for hot-update js files
      // It only happens in Webpack 2, where hot updates are emitted separately before the full bundle
      if (self.isHotUpdateCompilation(assets)) {
        return callback();
      }

      // If the template and the assets did not change we don't have to emit the html
      const assetJson = JSON.stringify(self.getAssetFiles(assets));
      if (isCompilationCached && self.options.cache && assetJson === self.assetJson) {
        return callback();
      } else {
        self.assetJson = assetJson;
      }

      Promise.resolve()
        // Favicon
        .then(() => {
          if (self.options.favicon) {
            return self.addFileToAssets(self.options.favicon, compilation)
              .then(faviconBasename => {
                let publicPath = compilation.mainTemplate.getPublicPath({hash: compilation.hash}) || '';
                if (publicPath && publicPath.substr(-1) !== '/') {
                  publicPath += '/';
                }
                assets.favicon = publicPath + faviconBasename;
              });
          }
        })
        // Wait for the compilation to finish
        .then(() => compilationPromise)
        .then(compiledTemplate => {
          // Allow to use a custom function / string instead
          if (self.options.templateContent !== undefined) {
            return self.options.templateContent;
          }
          // Once everything is compiled evaluate the html factory
          // and replace it with its content
          return self.evaluateCompilationResult(compilation, compiledTemplate);
        })
        // Allow plugins to make changes to the assets before invoking the template
        // This only makes sense to use if `inject` is `false`
        .then(compilationResult => applyPluginsAsyncWaterfall('html-webpack-plugin-before-html-generation', false, {
          assets: assets,
          outputName: self.childCompilationOutputName,
          plugin: self
        })
      .then(() => compilationResult))
        // Execute the template
        .then(compilationResult => typeof compilationResult !== 'function'
        ? compilationResult
        : self.executeTemplate(compilationResult, chunks, assets, compilation))
        // Allow plugins to change the html before assets are injected
        .then(html => {
          const pluginArgs = {html: html, assets: assets, plugin: self, outputName: self.childCompilationOutputName};
          return applyPluginsAsyncWaterfall('html-webpack-plugin-before-html-processing', true, pluginArgs);
        })
        .then(result => {
          const html = result.html;
          const assets = result.assets;
          // Prepare script and link tags
          const assetTags = self.generateHtmlTags(assets);
          const pluginArgs = {head: assetTags.head, body: assetTags.body, plugin: self, chunks: chunks, outputName: self.childCompilationOutputName};
          // Allow plugins to change the assetTag definitions
          return applyPluginsAsyncWaterfall('html-webpack-plugin-alter-asset-tags', true, pluginArgs)
            .then(result => self.postProcessHtml(html, assets, { body: result.body, head: result.head })
            .then(html => _.extend(result, {html: html, assets: assets})));
        })
        // Allow plugins to change the html after assets are injected
        .then(result => {
          const html = result.html;
          const assets = result.assets;
          const pluginArgs = {html: html, assets: assets, plugin: self, outputName: self.childCompilationOutputName};
          return applyPluginsAsyncWaterfall('html-webpack-plugin-after-html-processing', true, pluginArgs)
            .then(result => result.html);
        })
        .catch(err => {
          // In case anything went wrong the promise is resolved
          // with the error message and an error is logged
          compilation.errors.push(prettyError(err, compiler.context).toString());
          // Prevent caching
          self.hash = null;
          return self.options.showErrors ? prettyError(err, compiler.context).toHtml() : 'ERROR';
        })
        .then(html => {
          // Replace the compilation result with the evaluated html code
          compilation.assets[self.childCompilationOutputName] = {
            source: () => html,
            size: () => html.length
          };
        })
        .then(() => applyPluginsAsyncWaterfall('html-webpack-plugin-after-emit', false, {
          html: compilation.assets[self.childCompilationOutputName],
          outputName: self.childCompilationOutputName,
          plugin: self
        }).catch(err => {
          console.error(err);
          return null;
        }).then(() => null))
        // Let webpack continue with it
        .then(() => {
          callback();
        });
    });
  }

  /**
   * Evaluates the child compilation result
   * Returns a promise
   */
  evaluateCompilationResult (compilation, source) {
    if (!source) {
      return Promise.reject('The child compilation didn\'t provide a result');
    }

    // The LibraryTemplatePlugin stores the template result in a local variable.
    // To extract the result during the evaluation this part has to be removed.
    source = source.replace('var HTML_WEBPACK_PLUGIN_RESULT =', '');
    const template = this.options.template.replace(/^.+!/, '').replace(/\?.+$/, '');
    const vmContext = vm.createContext(_.extend({HTML_WEBPACK_PLUGIN: true, require: require}, global));
    const vmScript = new vm.Script(source, {filename: template});
    // Evaluate code and cast to string
    let newSource;
    try {
      newSource = vmScript.runInContext(vmContext);
    } catch (e) {
      return Promise.reject(e);
    }
    if (typeof newSource === 'object' && newSource.__esModule && newSource.default) {
      newSource = newSource.default;
    }
    return typeof newSource === 'string' || typeof newSource === 'function'
      ? Promise.resolve(newSource)
      : Promise.reject('The loader "' + this.options.template + '" didn\'t return html.');
  }

  /**
   * Generate the template parameters for the template function
   */
  getTemplateParameters (compilation, assets) {
    if (typeof this.options.templateParameters === 'function') {
      return this.options.templateParameters(compilation, assets, this.options);
    }
    if (typeof this.options.templateParameters === 'object') {
      return this.options.templateParameters;
    }
    return {};
  }

  /**
   * Html post processing
   *
   * Returns a promise
   */
  executeTemplate (templateFunction, chunks, assets, compilation) {
    return Promise.resolve()
      // Template processing
      .then(() => {
        const templateParams = this.getTemplateParameters(compilation, assets);
        let html = '';
        try {
          html = templateFunction(templateParams);
        } catch (e) {
          compilation.errors.push(new Error('Template execution failed: ' + e));
          return Promise.reject(e);
        }
        return html;
      });
  }

  /**
   * Html post processing
   *
   * Returns a promise
   */
  postProcessHtml (html, assets, assetTags) {
    const self = this;
    if (typeof html !== 'string') {
      return Promise.reject('Expected html to be a string but got ' + JSON.stringify(html));
    }
    return Promise.resolve()
      // Inject
      .then(() => {
        if (self.options.inject) {
          return self.injectAssetsIntoHtml(html, assets, assetTags);
        } else {
          return html;
        }
      })
      // Minify
      .then(html => {
        if (self.options.minify) {
          const minify = require('html-minifier').minify;
          return minify(html, self.options.minify);
        }
        return html;
      });
  }

  /*
   * Pushes the content of the given filename to the compilation assets
   */
  addFileToAssets (filename, compilation) {
    filename = path.resolve(compilation.compiler.context, filename);
    return Promise.all([
      fsStatAsync(filename),
      fsReadFileAsync(filename)
    ])
    .then(([size, source]) => {
      return {
        size,
        source
      };
    })
    .catch(() => Promise.reject(new Error('HtmlWebpackPlugin: could not load file ' + filename)))
    .then(results => {
      const basename = path.basename(filename);
      if (compilation.fileDependencies.add) {
        compilation.fileDependencies.add(filename);
      } else {
        // Before Webpack 4 - fileDepenencies was an array
        compilation.fileDependencies.push(filename);
      }
      compilation.assets[basename] = {
        source: () => results.source,
        size: () => results.size.size
      };
      return basename;
    });
  }

  /**
   * Helper to sort chunks
   */
  sortChunks (chunks, sortMode, compilation) {
    // Custom function
    if (typeof sortMode === 'function') {
      return chunks.sort(sortMode);
    }
    // Check if the given sort mode is a valid chunkSorter sort mode
    if (typeof chunkSorter[sortMode] !== 'undefined') {
      return chunkSorter[sortMode](chunks, this.options, compilation);
    }
    throw new Error('"' + sortMode + '" is not a valid chunk sort mode');
  }

  /**
   * Return all chunks from the compilation result which match the exclude and include filters
   */
  filterChunks (chunks, includedChunks, excludedChunks) {
    return chunks.filter(chunk => {
      const chunkName = chunk.names[0];
      // This chunk doesn't have a name. This script can't handled it.
      if (chunkName === undefined) {
        return false;
      }
      // Skip if the chunk should be lazy loaded
      if (typeof chunk.isInitial === 'function') {
        if (!chunk.isInitial()) {
          return false;
        }
      } else if (!chunk.initial) {
        return false;
      }
      // Skip if the chunks should be filtered and the given chunk was not added explicity
      if (Array.isArray(includedChunks) && includedChunks.indexOf(chunkName) === -1) {
        return false;
      }
      // Skip if the chunks should be filtered and the given chunk was excluded explicity
      if (Array.isArray(excludedChunks) && excludedChunks.indexOf(chunkName) !== -1) {
        return false;
      }
      // Add otherwise
      return true;
    });
  }

  isHotUpdateCompilation (assets) {
    return assets.js.length && assets.js.every(name => /\.hot-update\.js$/.test(name));
  }

  htmlWebpackPluginAssets (compilation, chunks) {
    const self = this;
    const compilationHash = compilation.hash;

    // Use the configured public path or build a relative path
    let publicPath = typeof compilation.options.output.publicPath !== 'undefined'
      // If a hard coded public path exists use it
      ? compilation.mainTemplate.getPublicPath({hash: compilationHash})
      // If no public path was set get a relative url path
      : path.relative(path.resolve(compilation.options.output.path, path.dirname(self.childCompilationOutputName)), compilation.options.output.path)
        .split(path.sep).join('/');

    if (publicPath.length && publicPath.substr(-1, 1) !== '/') {
      publicPath += '/';
    }

    const assets = {
      // The public path
      publicPath: publicPath,
      // Will contain all js & css files by chunk
      chunks: {},
      // Will contain all js files
      js: [],
      // Will contain all css files
      css: [],
      // Will contain the html5 appcache manifest files if it exists
      manifest: Object.keys(compilation.assets).filter(assetFile => path.extname(assetFile) === '.appcache')[0]
    };

    // Append a hash for cache busting
    if (this.options.hash) {
      assets.manifest = self.appendHash(assets.manifest, compilationHash);
      assets.favicon = self.appendHash(assets.favicon, compilationHash);
    }

    for (let i = 0; i < chunks.length; i++) {
      const chunk = chunks[i];
      const chunkName = chunk.names[0];

      assets.chunks[chunkName] = {};

      // Prepend the public path to all chunk files
      let chunkFiles = [].concat(chunk.files).map(chunkFile => publicPath + chunkFile);

      // Append a hash for cache busting
      if (this.options.hash) {
        chunkFiles = chunkFiles.map(chunkFile => self.appendHash(chunkFile, compilationHash));
      }

      // Webpack outputs an array for each chunk when using sourcemaps
      // or when one chunk hosts js and css simultaneously
      const js = chunkFiles.find(chunkFile => /.js($|\?)/.test(chunkFile));
      if (js) {
        assets.chunks[chunkName].size = chunk.size;
        assets.chunks[chunkName].entry = js;
        assets.chunks[chunkName].hash = chunk.hash;
        assets.js.push(js);
      }

      // Gather all css files
      const css = chunkFiles.filter(chunkFile => /.css($|\?)/.test(chunkFile));
      assets.chunks[chunkName].css = css;
      assets.css = assets.css.concat(css);
    }

    // Duplicate css assets can occur on occasion if more than one chunk
    // requires the same css.
    assets.css = _.uniq(assets.css);

    return assets;
  }

  /**
   * Generate meta tags
   */
  getMetaTags () {
    if (this.options.meta === false) {
      return [];
    }
    // Make tags self-closing in case of xhtml
    // Turn { "viewport" : "width=500, initial-scale=1" } into
    // [{ name:"viewport" content:"width=500, initial-scale=1" }]
    const selfClosingTag = !!this.options.xhtml;
    const metaTagAttributeObjects = Object.keys(this.options.meta).map((metaName) => {
      const metaTagContent = this.options.meta[metaName];
      return (typeof metaTagContent === 'object') ? metaTagContent : {
        name: metaName,
        content: metaTagContent
      };
    });
    // Turn [{ name:"viewport" content:"width=500, initial-scale=1" }] into
    // the html-webpack-plugin tag structure
    return metaTagAttributeObjects.map((metaTagAttributes) => {
      return {
        tagName: 'meta',
        voidTag: true,
        selfClosingTag: selfClosingTag,
        attributes: metaTagAttributes
      };
    });
  }

  /**
   * Injects the assets into the given html string
   */
  generateHtmlTags (assets) {
    // Turn script files into script tags
    const scripts = assets.js.map(scriptPath => ({
      tagName: 'script',
      closeTag: true,
      attributes: {
        type: 'text/javascript',
        src: scriptPath
      }
    }));
    // Make tags self-closing in case of xhtml
    const selfClosingTag = !!this.options.xhtml;
    // Turn css files into link tags
    const styles = assets.css.map(stylePath => ({
      tagName: 'link',
      selfClosingTag: selfClosingTag,
      voidTag: true,
      attributes: {
        href: stylePath,
        rel: 'stylesheet'
      }
    }));
    // Injection targets
    let head = this.getMetaTags();
    let body = [];

    // If there is a favicon present, add it to the head
    if (assets.favicon) {
      head.push({
        tagName: 'link',
        selfClosingTag: selfClosingTag,
        voidTag: true,
        attributes: {
          rel: 'shortcut icon',
          href: assets.favicon
        }
      });
    }
    // Add styles to the head
    head = head.concat(styles);
    // Add scripts to body or head
    if (this.options.inject === 'head') {
      head = head.concat(scripts);
    } else {
      body = body.concat(scripts);
    }
    return {head: head, body: body};
  }

  /**
   * Injects the assets into the given html string
   */
  injectAssetsIntoHtml (html, assets, assetTags) {
    const htmlRegExp = /(<html[^>]*>)/i;
    const headRegExp = /(<\/head\s*>)/i;
    const bodyRegExp = /(<\/body\s*>)/i;
    const body = assetTags.body.map(this.createHtmlTag.bind(this));
    const head = assetTags.head.map(this.createHtmlTag.bind(this));

    if (body.length) {
      if (bodyRegExp.test(html)) {
        // Append assets to body element
        html = html.replace(bodyRegExp, match => body.join('') + match);
      } else {
        // Append scripts to the end of the file if no <body> element exists:
        html += body.join('');
      }
    }

    if (head.length) {
      // Create a head tag if none exists
      if (!headRegExp.test(html)) {
        if (!htmlRegExp.test(html)) {
          html = '<head></head>' + html;
        } else {
          html = html.replace(htmlRegExp, match => match + '<head></head>');
        }
      }

      // Append assets to head element
      html = html.replace(headRegExp, match => head.join('') + match);
    }

    // Inject manifest into the opening html tag
    if (assets.manifest) {
      html = html.replace(/(<html[^>]*)(>)/i, (match, start, end) => {
        // Append the manifest only if no manifest was specified
        if (/\smanifest\s*=/.test(match)) {
          return match;
        }
        return start + ' manifest="' + assets.manifest + '"' + end;
      });
    }
    return html;
  }

  /**
   * Appends a cache busting hash
   */
  appendHash (url, hash) {
    if (!url) {
      return url;
    }
    return url + (url.indexOf('?') === -1 ? '?' : '&') + hash;
  }

  /**
   * Turn a tag definition into a html string
   */
  createHtmlTag (tagDefinition) {
    const attributes = Object.keys(tagDefinition.attributes || {})
      .filter(attributeName => tagDefinition.attributes[attributeName] !== false)
      .map(attributeName => {
        if (tagDefinition.attributes[attributeName] === true) {
          return attributeName;
        }
        return attributeName + '="' + tagDefinition.attributes[attributeName] + '"';
      });
    // Backport of 3.x void tag definition
    const voidTag = tagDefinition.voidTag !== undefined ? tagDefinition.voidTag : !tagDefinition.closeTag;
    const selfClosingTag = tagDefinition.voidTag !== undefined ? tagDefinition.voidTag && this.options.xhtml : tagDefinition.selfClosingTag;
    return '<' + [tagDefinition.tagName].concat(attributes).join(' ') + (selfClosingTag ? '/' : '') + '>' +
      (tagDefinition.innerHTML || '') +
      (voidTag ? '' : '</' + tagDefinition.tagName + '>');
  }

  /**
   * Helper to return the absolute template path with a fallback loader
   */
  getFullTemplatePath (template, context) {
    // If the template doesn't use a loader use the lodash template loader
    if (template.indexOf('!') === -1) {
      template = require.resolve('./lib/loader.js') + '!' + path.resolve(context, template);
    }
    // Resolve template path
    return template.replace(
      /([!])([^/\\][^!?]+|[^/\\!?])($|\?[^!?\n]+$)/,
      (match, prefix, filepath, postfix) => prefix + path.resolve(filepath) + postfix);
  }

  /**
   * Helper to return a sorted unique array of all asset files out of the
   * asset object
   */
  getAssetFiles (assets) {
    const files = _.uniq(Object.keys(assets).filter(assetType => assetType !== 'chunks' && assets[assetType]).reduce((files, assetType) => files.concat(assets[assetType]), []));
    files.sort();
    return files;
  }

  /**
   * Helper to promisify compilation.applyPluginsAsyncWaterfall that returns
   * a function that helps to merge given plugin arguments with processed ones
   */
  applyPluginsAsyncWaterfall (compilation) {
    if (compilation.hooks) {
      return (eventName, requiresResult, pluginArgs) => {
        const ccEventName = trainCaseToCamelCase(eventName);
        if (!compilation.hooks[ccEventName]) {
          compilation.errors.push(
            new Error('No hook found for ' + eventName)
          );
        }

        return compilation.hooks[ccEventName].promise(pluginArgs);
      };
    }

    // Before Webpack 4
    const promisedApplyPluginsAsyncWaterfall = function (name, init) {
      return new Promise((resolve, reject) => {
        const callback = function (err, result) {
          if (err) {
            return reject(err);
          }
          resolve(result);
        };
        compilation.applyPluginsAsyncWaterfall(name, init, callback);
      });
    };

    return (eventName, requiresResult, pluginArgs) => promisedApplyPluginsAsyncWaterfall(eventName, pluginArgs)
      .then(result => {
        if (requiresResult && !result) {
          compilation.warnings.push(
            new Error('Using ' + eventName + ' without returning a result is deprecated.')
          );
        }
        return _.extend(pluginArgs, result);
      });
  }
}

/**
 * Takes a string in train case and transforms it to camel case
 *
 * Example: 'hello-my-world' to 'helloMyWorld'
 *
 * @param {string} word
 */
function trainCaseToCamelCase (word) {
  return word.replace(/-([\w])/g, (match, p1) => p1.toUpperCase());
}

/**
 * The default for options.templateParameter
 * Generate the template parameters
 */
function templateParametersGenerator (compilation, assets, options) {
  return {
    compilation: compilation,
    webpack: compilation.getStats().toJson(),
    webpackConfig: compilation.options,
    htmlWebpackPlugin: {
      files: assets,
      options: options
    }
  };
}

module.exports = HtmlWebpackPlugin;