716 lines
24 KiB
JavaScript
716 lines
24 KiB
JavaScript
/**
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* Copyright 2018 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not
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* use this file except in compliance with the License. You may obtain a copy of
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* the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations under
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* the License.
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*/
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import path from 'path';
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import { readFile } from 'fs';
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import prettyBytes from 'pretty-bytes';
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import { createDocument, serializeDocument } from './dom';
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import {
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parseStylesheet,
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serializeStylesheet,
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walkStyleRules,
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walkStyleRulesWithReverseMirror,
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markOnly,
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applyMarkedSelectors
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} from './css';
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import { createLogger } from './util';
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/**
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* The mechanism to use for lazy-loading stylesheets.
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*
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* Note: <kbd>JS</kbd> indicates a strategy requiring JavaScript (falls back to `<noscript>` unless disabled).
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*
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* - **default:** Move stylesheet links to the end of the document and insert preload meta tags in their place.
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* - **"body":** Move all external stylesheet links to the end of the document.
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* - **"media":** Load stylesheets asynchronously by adding `media="not x"` and removing once loaded. <kbd>JS</kbd>
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* - **"swap":** Convert stylesheet links to preloads that swap to `rel="stylesheet"` once loaded ([details](https://www.filamentgroup.com/lab/load-css-simpler/#the-code)). <kbd>JS</kbd>
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* - **"swap-high":** Use `<link rel="alternate stylesheet preload">` and swap to `rel="stylesheet"` once loaded ([details](http://filamentgroup.github.io/loadCSS/test/new-high.html)). <kbd>JS</kbd>
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* - **"js":** Inject an asynchronous CSS loader similar to [LoadCSS](https://github.com/filamentgroup/loadCSS) and use it to load stylesheets. <kbd>JS</kbd>
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* - **"js-lazy":** Like `"js"`, but the stylesheet is disabled until fully loaded.
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* - **false:** Disables adding preload tags.
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* @typedef {(default|'body'|'media'|'swap'|'swap-high'|'js'|'js-lazy')} PreloadStrategy
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* @public
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*/
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/**
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* Controls which keyframes rules are inlined.
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*
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* - **"critical":** _(default)_ inline keyframes rules that are used by the critical CSS.
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* - **"all":** Inline all keyframes rules.
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* - **"none":** Remove all keyframes rules.
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* @typedef {('critical'|'all'|'none')} KeyframeStrategy
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* @private
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* @property {String} keyframes Which {@link KeyframeStrategy keyframe strategy} to use (default: `critical`)_
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*/
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/**
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* Controls log level of the plugin. Specifies the level the logger should use. A logger will
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* not produce output for any log level beneath the specified level. Available levels and order
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* are:
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*
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* - **"info"** _(default)_
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* - **"warn"**
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* - **"error"**
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* - **"trace"**
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* - **"debug"**
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* - **"silent"**
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* @typedef {('info'|'warn'|'error'|'trace'|'debug'|'silent')} LogLevel
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* @public
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*/
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/**
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* Custom logger interface:
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* @typedef {object} Logger
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* @public
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* @property {function(String)} trace - Prints a trace message
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* @property {function(String)} debug - Prints a debug message
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* @property {function(String)} info - Prints an information message
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* @property {function(String)} warn - Prints a warning message
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* @property {function(String)} error - Prints an error message
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*/
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/**
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* All optional. Pass them to `new Critters({ ... })`.
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* @public
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* @typedef Options
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* @property {String} path Base path location of the CSS files _(default: `''`)_
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* @property {String} publicPath Public path of the CSS resources. This prefix is removed from the href _(default: `''`)_
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* @property {Boolean} external Inline styles from external stylesheets _(default: `true`)_
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* @property {Number} inlineThreshold Inline external stylesheets smaller than a given size _(default: `0`)_
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* @property {Number} minimumExternalSize If the non-critical external stylesheet would be below this size, just inline it _(default: `0`)_
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* @property {Boolean} pruneSource Remove inlined rules from the external stylesheet _(default: `false`)_
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* @property {Boolean} mergeStylesheets Merged inlined stylesheets into a single `<style>` tag _(default: `true`)_
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* @property {String[]} additionalStylesheets Glob for matching other stylesheets to be used while looking for critical CSS.
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* @property {String} preload Which {@link PreloadStrategy preload strategy} to use
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* @property {Boolean} noscriptFallback Add `<noscript>` fallback to JS-based strategies
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* @property {Boolean} inlineFonts Inline critical font-face rules _(default: `false`)_
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* @property {Boolean} preloadFonts Preloads critical fonts _(default: `true`)_
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* @property {Boolean} fonts Shorthand for setting `inlineFonts` + `preloadFonts`
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* - Values:
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* - `true` to inline critical font-face rules and preload the fonts
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* - `false` to don't inline any font-face rules and don't preload fonts
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* @property {String} keyframes Controls which keyframes rules are inlined.
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* - Values:
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* - `"critical"`: _(default)_ inline keyframes rules used by the critical CSS
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* - `"all"` inline all keyframes rules
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* - `"none"` remove all keyframes rules
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* @property {Boolean} compress Compress resulting critical CSS _(default: `true`)_
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* @property {String} logLevel Controls {@link LogLevel log level} of the plugin _(default: `"info"`)_
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* @property {object} logger Provide a custom logger interface {@link Logger logger}
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*/
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export default class Critters {
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/** @private */
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constructor(options) {
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this.options = Object.assign(
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{
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logLevel: 'info',
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path: '',
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publicPath: '',
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reduceInlineStyles: true,
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pruneSource: false,
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additionalStylesheets: [],
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allowRules: []
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},
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options || {}
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);
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this.urlFilter = this.options.filter;
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if (this.urlFilter instanceof RegExp) {
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this.urlFilter = this.urlFilter.test.bind(this.urlFilter);
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}
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this.logger = this.options.logger || createLogger(this.options.logLevel);
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}
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/**
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* Read the contents of a file from the specified filesystem or disk
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*/
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readFile(filename) {
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const fs = this.fs;
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return new Promise((resolve, reject) => {
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const callback = (err, data) => {
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if (err) reject(err);
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else resolve(data);
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};
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if (fs && fs.readFile) {
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fs.readFile(filename, callback);
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} else {
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readFile(filename, 'utf8', callback);
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}
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});
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}
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/**
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* Apply critical CSS processing to the html
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*/
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async process(html) {
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const start = process.hrtime.bigint();
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// Parse the generated HTML in a DOM we can mutate
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const document = createDocument(html);
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if (this.options.additionalStylesheets.length > 0) {
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this.embedAdditionalStylesheet(document);
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}
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// `external:false` skips processing of external sheets
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if (this.options.external !== false) {
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const externalSheets = [].slice.call(
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document.querySelectorAll('link[rel="stylesheet"]')
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);
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await Promise.all(
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externalSheets.map((link) => this.embedLinkedStylesheet(link, document))
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);
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}
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// go through all the style tags in the document and reduce them to only critical CSS
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const styles = this.getAffectedStyleTags(document);
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await Promise.all(
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styles.map((style) => this.processStyle(style, document))
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);
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if (this.options.mergeStylesheets !== false && styles.length !== 0) {
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await this.mergeStylesheets(document);
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}
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// serialize the document back to HTML and we're done
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const output = serializeDocument(document);
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const end = process.hrtime.bigint();
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this.logger.info('Time ' + parseFloat(end - start) / 1000000.0);
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return output;
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}
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/**
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* Get the style tags that need processing
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*/
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getAffectedStyleTags(document) {
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const styles = [].slice.call(document.querySelectorAll('style'));
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// `inline:false` skips processing of inline stylesheets
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if (this.options.reduceInlineStyles === false) {
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return styles.filter((style) => style.$$external);
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}
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return styles;
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}
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async mergeStylesheets(document) {
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const styles = this.getAffectedStyleTags(document);
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if (styles.length === 0) {
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this.logger.warn(
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'Merging inline stylesheets into a single <style> tag skipped, no inline stylesheets to merge'
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);
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return;
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}
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const first = styles[0];
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let sheet = first.textContent;
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for (let i = 1; i < styles.length; i++) {
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const node = styles[i];
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sheet += node.textContent;
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node.remove();
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}
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first.textContent = sheet;
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}
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/**
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* Given href, find the corresponding CSS asset
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*/
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async getCssAsset(href) {
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const outputPath = this.options.path;
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const publicPath = this.options.publicPath;
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// CHECK - the output path
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// path on disk (with output.publicPath removed)
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let normalizedPath = href.replace(/^\//, '');
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const pathPrefix = (publicPath || '').replace(/(^\/|\/$)/g, '') + '/';
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if (normalizedPath.indexOf(pathPrefix) === 0) {
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normalizedPath = normalizedPath
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.substring(pathPrefix.length)
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.replace(/^\//, '');
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}
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// Ignore remote stylesheets
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if (/^https?:\/\//.test(normalizedPath) || href.startsWith('//')) {
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return undefined;
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}
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const filename = path.resolve(outputPath, normalizedPath);
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let sheet;
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try {
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sheet = await this.readFile(filename);
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} catch (e) {
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this.logger.warn(`Unable to locate stylesheet: ${filename}`);
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}
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return sheet;
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}
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checkInlineThreshold(link, style, sheet) {
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if (
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this.options.inlineThreshold &&
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sheet.length < this.options.inlineThreshold
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) {
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const href = style.$$name;
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style.$$reduce = false;
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this.logger.info(
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`\u001b[32mInlined all of ${href} (${sheet.length} was below the threshold of ${this.options.inlineThreshold})\u001b[39m`
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);
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link.remove();
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return true;
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}
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return false;
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}
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/**
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* Inline the stylesheets from options.additionalStylesheets (assuming it passes `options.filter`)
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*/
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async embedAdditionalStylesheet(document) {
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const styleSheetsIncluded = [];
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const sources = await Promise.all(
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this.options.additionalStylesheets.map((cssFile) => {
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if (styleSheetsIncluded.includes(cssFile)) {
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return;
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}
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styleSheetsIncluded.push(cssFile);
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const style = document.createElement('style');
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style.$$external = true;
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return this.getCssAsset(cssFile, style).then((sheet) => [sheet, style]);
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})
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);
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sources.forEach(([sheet, style]) => {
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if (!sheet) return;
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style.textContent = sheet;
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document.head.appendChild(style);
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});
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}
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/**
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* Inline the target stylesheet referred to by a <link rel="stylesheet"> (assuming it passes `options.filter`)
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*/
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async embedLinkedStylesheet(link, document) {
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const href = link.getAttribute('href');
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const media = link.getAttribute('media');
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const preloadMode = this.options.preload;
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// skip filtered resources, or network resources if no filter is provided
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if (this.urlFilter ? this.urlFilter(href) : !(href || '').match(/\.css$/)) {
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return Promise.resolve();
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}
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// the reduced critical CSS gets injected into a new <style> tag
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const style = document.createElement('style');
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style.$$external = true;
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const sheet = await this.getCssAsset(href, style);
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if (!sheet) {
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return;
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}
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style.textContent = sheet;
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style.$$name = href;
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style.$$links = [link];
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link.parentNode.insertBefore(style, link);
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if (this.checkInlineThreshold(link, style, sheet)) {
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return;
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}
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// CSS loader is only injected for the first sheet, then this becomes an empty string
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let cssLoaderPreamble =
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"function $loadcss(u,m,l){(l=document.createElement('link')).rel='stylesheet';l.href=u;document.head.appendChild(l)}";
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const lazy = preloadMode === 'js-lazy';
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if (lazy) {
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cssLoaderPreamble = cssLoaderPreamble.replace(
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'l.href',
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"l.media='print';l.onload=function(){l.media=m};l.href"
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);
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}
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// Allow disabling any mutation of the stylesheet link:
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if (preloadMode === false) return;
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let noscriptFallback = false;
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if (preloadMode === 'body') {
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document.body.appendChild(link);
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} else {
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link.setAttribute('rel', 'preload');
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link.setAttribute('as', 'style');
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if (preloadMode === 'js' || preloadMode === 'js-lazy') {
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const script = document.createElement('script');
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const js = `${cssLoaderPreamble}$loadcss(${JSON.stringify(href)}${
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lazy ? ',' + JSON.stringify(media || 'all') : ''
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})`;
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// script.appendChild(document.createTextNode(js));
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script.textContent = js;
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link.parentNode.insertBefore(script, link.nextSibling);
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style.$$links.push(script);
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cssLoaderPreamble = '';
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noscriptFallback = true;
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} else if (preloadMode === 'media') {
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// @see https://github.com/filamentgroup/loadCSS/blob/af1106cfe0bf70147e22185afa7ead96c01dec48/src/loadCSS.js#L26
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link.setAttribute('rel', 'stylesheet');
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link.removeAttribute('as');
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link.setAttribute('media', 'print');
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link.setAttribute('onload', `this.media='${media || 'all'}'`);
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noscriptFallback = true;
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} else if (preloadMode === 'swap-high') {
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// @see http://filamentgroup.github.io/loadCSS/test/new-high.html
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link.setAttribute('rel', 'alternate stylesheet preload');
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link.setAttribute('title', 'styles');
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link.setAttribute('onload', `this.title='';this.rel='stylesheet'`);
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noscriptFallback = true;
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} else if (preloadMode === 'swap') {
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link.setAttribute('onload', "this.rel='stylesheet'");
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noscriptFallback = true;
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} else {
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const bodyLink = document.createElement('link');
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bodyLink.setAttribute('rel', 'stylesheet');
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if (media) bodyLink.setAttribute('media', media);
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bodyLink.setAttribute('href', href);
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document.body.appendChild(bodyLink);
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style.$$links.push(bodyLink);
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}
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}
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if (this.options.noscriptFallback !== false && noscriptFallback) {
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const noscript = document.createElement('noscript');
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const noscriptLink = document.createElement('link');
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noscriptLink.setAttribute('rel', 'stylesheet');
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noscriptLink.setAttribute('href', href);
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if (media) noscriptLink.setAttribute('media', media);
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noscript.appendChild(noscriptLink);
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link.parentNode.insertBefore(noscript, link.nextSibling);
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style.$$links.push(noscript);
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}
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}
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/**
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* Prune the source CSS files
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*/
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pruneSource(style, before, sheetInverse) {
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// if external stylesheet would be below minimum size, just inline everything
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const minSize = this.options.minimumExternalSize;
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const name = style.$$name;
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if (minSize && sheetInverse.length < minSize) {
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this.logger.info(
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`\u001b[32mInlined all of ${name} (non-critical external stylesheet would have been ${sheetInverse.length}b, which was below the threshold of ${minSize})\u001b[39m`
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);
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style.textContent = before;
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// remove any associated external resources/loaders:
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if (style.$$links) {
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for (const link of style.$$links) {
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const parent = link.parentNode;
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if (parent) parent.removeChild(link);
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}
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}
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return true;
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}
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return false;
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}
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/**
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* Parse the stylesheet within a <style> element, then reduce it to contain only rules used by the document.
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*/
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async processStyle(style, document) {
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if (style.$$reduce === false) return;
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const name = style.$$name ? style.$$name.replace(/^\//, '') : 'inline CSS';
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const options = this.options;
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const crittersContainer = document.crittersContainer;
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let keyframesMode = options.keyframes || 'critical';
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// we also accept a boolean value for options.keyframes
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if (keyframesMode === true) keyframesMode = 'all';
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if (keyframesMode === false) keyframesMode = 'none';
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let sheet = style.textContent;
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// store a reference to the previous serialized stylesheet for reporting stats
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const before = sheet;
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// Skip empty stylesheets
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if (!sheet) return;
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const ast = parseStylesheet(sheet);
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const astInverse = options.pruneSource ? parseStylesheet(sheet) : null;
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// a string to search for font names (very loose)
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let criticalFonts = '';
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const failedSelectors = [];
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const criticalKeyframeNames = [];
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let includeNext = false;
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let includeAll = false;
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let excludeNext = false;
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let excludeAll = false;
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// Walk all CSS rules, marking unused rules with `.$$remove=true` for removal in the second pass.
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// This first pass is also used to collect font and keyframe usage used in the second pass.
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walkStyleRules(
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ast,
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markOnly((rule) => {
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if (rule.type === 'comment') {
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const comment = rule.text.trim();
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if (comment.startsWith('critters')) {
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const command = comment.replace(/^critters:/, '');
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switch (command) {
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case 'include':
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includeNext = true;
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break;
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case 'exclude':
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excludeNext = true;
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break;
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case 'include start':
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includeAll = true;
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break;
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case 'include end':
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includeAll = false;
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break;
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case 'exclude start':
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excludeAll = true;
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break;
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case 'exclude end':
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excludeAll = false;
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break;
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}
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|
}
|
|
}
|
|
|
|
if (rule.type === 'rule') {
|
|
// Handle comment based markers
|
|
if (includeNext) {
|
|
includeNext = false;
|
|
return true;
|
|
}
|
|
|
|
if (excludeNext) {
|
|
excludeNext = false;
|
|
return false;
|
|
}
|
|
|
|
if (includeAll) {
|
|
return true;
|
|
}
|
|
|
|
if (excludeAll) {
|
|
return false;
|
|
}
|
|
|
|
// Filter the selector list down to only those match
|
|
rule.filterSelectors((sel) => {
|
|
// Validate rule with 'allowRules' option
|
|
const isAllowedRule = options.allowRules.some((exp) => {
|
|
if (exp instanceof RegExp) {
|
|
return exp.test(sel);
|
|
}
|
|
return exp === sel;
|
|
});
|
|
if (isAllowedRule) return true;
|
|
|
|
// Strip pseudo-elements and pseudo-classes, since we only care that their associated elements exist.
|
|
// This means any selector for a pseudo-element or having a pseudo-class will be inlined if the rest of the selector matches.
|
|
if (
|
|
sel === ':root' ||
|
|
sel.match(/^::?(before|after)$/) ||
|
|
sel === 'html' ||
|
|
sel === 'body'
|
|
) {
|
|
return true;
|
|
}
|
|
sel = sel
|
|
.replace(/(?<!\\)::?[a-z-]+(?![a-z-(])/gi, '')
|
|
.replace(/::?not\(\s*\)/g, '')
|
|
// Remove tailing or leading commas from cleaned sub selector `is(.active, :hover)` -> `is(.active)`.
|
|
.replace(/\(\s*,/g, '(')
|
|
.replace(/,\s*\)/g, ')')
|
|
.trim();
|
|
if (!sel) return false;
|
|
|
|
try {
|
|
return crittersContainer.exists(sel);
|
|
} catch (e) {
|
|
failedSelectors.push(sel + ' -> ' + e.message);
|
|
return false;
|
|
}
|
|
});
|
|
|
|
// If there are no matched selectors, remove the rule:
|
|
if (!rule.selector) {
|
|
return false;
|
|
}
|
|
|
|
if (rule.nodes) {
|
|
for (let i = 0; i < rule.nodes.length; i++) {
|
|
const decl = rule.nodes[i];
|
|
|
|
// detect used fonts
|
|
if (decl.prop && decl.prop.match(/\bfont(-family)?\b/i)) {
|
|
criticalFonts += ' ' + decl.value;
|
|
}
|
|
|
|
// detect used keyframes
|
|
if (decl.prop === 'animation' || decl.prop === 'animation-name') {
|
|
// @todo: parse animation declarations and extract only the name. for now we'll do a lazy match.
|
|
const names = decl.value.split(/\s+/);
|
|
for (let j = 0; j < names.length; j++) {
|
|
const name = names[j].trim();
|
|
if (name) criticalKeyframeNames.push(name);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// keep font rules, they're handled in the second pass:
|
|
if (rule.type === 'atrule' && rule.name === 'font-face') return;
|
|
|
|
// If there are no remaining rules, remove the whole rule:
|
|
const rules = rule.nodes && rule.nodes.filter((rule) => !rule.$$remove);
|
|
return !rules || rules.length !== 0;
|
|
})
|
|
);
|
|
|
|
if (failedSelectors.length !== 0) {
|
|
this.logger.warn(
|
|
`${
|
|
failedSelectors.length
|
|
} rules skipped due to selector errors:\n ${failedSelectors.join(
|
|
'\n '
|
|
)}`
|
|
);
|
|
}
|
|
|
|
const shouldPreloadFonts =
|
|
options.fonts === true || options.preloadFonts === true;
|
|
const shouldInlineFonts =
|
|
options.fonts !== false && options.inlineFonts === true;
|
|
|
|
const preloadedFonts = [];
|
|
// Second pass, using data picked up from the first
|
|
walkStyleRulesWithReverseMirror(ast, astInverse, (rule) => {
|
|
// remove any rules marked in the first pass
|
|
if (rule.$$remove === true) return false;
|
|
|
|
applyMarkedSelectors(rule);
|
|
|
|
// prune @keyframes rules
|
|
if (rule.type === 'atrule' && rule.name === 'keyframes') {
|
|
if (keyframesMode === 'none') return false;
|
|
if (keyframesMode === 'all') return true;
|
|
return criticalKeyframeNames.indexOf(rule.params) !== -1;
|
|
}
|
|
|
|
// prune @font-face rules
|
|
if (rule.type === 'atrule' && rule.name === 'font-face') {
|
|
let family, src;
|
|
for (let i = 0; i < rule.nodes.length; i++) {
|
|
const decl = rule.nodes[i];
|
|
if (decl.prop === 'src') {
|
|
// @todo parse this properly and generate multiple preloads with type="font/woff2" etc
|
|
src = (decl.value.match(/url\s*\(\s*(['"]?)(.+?)\1\s*\)/) || [])[2];
|
|
} else if (decl.prop === 'font-family') {
|
|
family = decl.value;
|
|
}
|
|
}
|
|
|
|
if (src && shouldPreloadFonts && preloadedFonts.indexOf(src) === -1) {
|
|
preloadedFonts.push(src);
|
|
const preload = document.createElement('link');
|
|
preload.setAttribute('rel', 'preload');
|
|
preload.setAttribute('as', 'font');
|
|
preload.setAttribute('crossorigin', 'anonymous');
|
|
preload.setAttribute('href', src.trim());
|
|
document.head.appendChild(preload);
|
|
}
|
|
|
|
// if we're missing info, if the font is unused, or if critical font inlining is disabled, remove the rule:
|
|
if (
|
|
!family ||
|
|
!src ||
|
|
criticalFonts.indexOf(family) === -1 ||
|
|
!shouldInlineFonts
|
|
) {
|
|
return false;
|
|
}
|
|
}
|
|
});
|
|
|
|
sheet = serializeStylesheet(ast, {
|
|
compress: this.options.compress !== false
|
|
});
|
|
|
|
// If all rules were removed, get rid of the style element entirely
|
|
if (sheet.trim().length === 0) {
|
|
if (style.parentNode) {
|
|
style.remove();
|
|
}
|
|
return;
|
|
}
|
|
|
|
let afterText = '';
|
|
let styleInlinedCompletely = false;
|
|
if (options.pruneSource) {
|
|
const sheetInverse = serializeStylesheet(astInverse, {
|
|
compress: this.options.compress !== false
|
|
});
|
|
|
|
styleInlinedCompletely = this.pruneSource(style, before, sheetInverse);
|
|
|
|
if (styleInlinedCompletely) {
|
|
const percent = (sheetInverse.length / before.length) * 100;
|
|
afterText = `, reducing non-inlined size ${
|
|
percent | 0
|
|
}% to ${prettyBytes(sheetInverse.length)}`;
|
|
}
|
|
}
|
|
|
|
// replace the inline stylesheet with its critical'd counterpart
|
|
if (!styleInlinedCompletely) {
|
|
style.textContent = sheet;
|
|
}
|
|
|
|
// output stats
|
|
const percent = ((sheet.length / before.length) * 100) | 0;
|
|
this.logger.info(
|
|
'\u001b[32mInlined ' +
|
|
prettyBytes(sheet.length) +
|
|
' (' +
|
|
percent +
|
|
'% of original ' +
|
|
prettyBytes(before.length) +
|
|
') of ' +
|
|
name +
|
|
afterText +
|
|
'.\u001b[39m'
|
|
);
|
|
}
|
|
}
|