Add util for webpack plugin to restrict languages

modifiers/prismjs.js

@@ -1,5 +1,5 @@
 /*
-Copyright 2022 DigitalOcean
+Copyright 2023 DigitalOcean
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -21,24 +21,17 @@ limitations under the License.
  */
 
 const Prism = require('../vendor/prismjs');
-const components = require('../vendor/prismjs/components');
 
 const safeObject = require('../util/safe_object');
 const findTagOpen = require('../util/find_tag_open');
 const findAttr = require('../util/find_attr');
+const { languages, languageAliases, getDependencies } = require('../util/prism_util');
 
 /**
  * @typedef {Object} PrismJsOptions
  * @property {string} [delimiter=','] String to split fence information on.
  */
 
-// Get languages that Prism supports
-const languages = new Set(Object.keys(components.languages).filter(lang => lang !== 'meta'));
-const languageAliases = Object.entries(components.languages).reduce((aliases, [ lang, { alias } ]) => {
-    if (alias) (Array.isArray(alias) ? alias : [ alias ]).forEach(a => { aliases[a] = lang; });
-    return aliases;
-}, {});
-
 /**
  * Helper to load in a language if not yet loaded.
  *
@@ -47,8 +40,12 @@ const languageAliases = Object.entries(components.languages).reduce((aliases, [
  */
 const loadLanguage = language => {
     if (language in Prism.languages) return;
-    // eslint-disable-next-line import/no-dynamic-require
-    require(`../vendor/prismjs/components/prism-${language}`)(Prism);
+    try {
+        // eslint-disable-next-line import/no-dynamic-require
+        require(`../vendor/prismjs/components/prism-${language}`)(Prism);
+    } catch (err) {
+        console.error('Failed to load Prism language', language, err);
+    }
 };
 
 // Load our HTML plugin
@@ -166,10 +163,12 @@ module.exports = (md, options) => {
             const { before, inside, after } = extractCodeBlock(rendered, language);
 
             // Load requirements for language
-            const comp = components.languages[language.clean];
-            if (comp.require) (Array.isArray(comp.require) ? comp.require : [ comp.require ]).forEach(loadLanguage);
+            getDependencies(language.clean).forEach(loadLanguage);
             loadLanguage(language.clean);
 
+            // If we failed to load the language (it's a dynamic require), return original
+            if (!(language.clean in Prism.languages)) return rendered;
+
             // Highlight the code with Prism
             const highlighted = Prism.highlight(inside, Prism.languages[language.clean], language.clean);
 

util/prism_util.js

@@ -0,0 +1,102 @@
+/*
+Copyright 2023 DigitalOcean
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+'use strict';
+
+/**
+ * @module util/prism_util
+ */
+
+const regexEscape = require('./regex_escape');
+const { languages: languagesData } = require('../vendor/prismjs/components');
+
+/**
+ * Deduplicate an array.
+ *
+ * @param {any[]} arr Array to deduplicate.
+ * @returns {any[]}
+ * @private
+ */
+const dedupe = arr => Array.from(new Set(arr));
+
+/**
+ * All languages that Prism supports.
+ *
+ * @type {Readonly<Set<string>>}
+ */
+const languages = Object.freeze(new Set(Object.keys(languagesData).filter(lang => lang !== 'meta')));
+
+/**
+ * Mapped Prism aliases to their language.
+ *
+ * @type {Readonly<Map<string, string>>}
+ */
+const languageAliases = Object.freeze(Object.entries(languagesData).reduce((aliases, [ lang, { alias } ]) => {
+    if (alias) (Array.isArray(alias) ? alias : [ alias ]).forEach(a => { aliases.set(a, lang); });
+    return aliases;
+}, new Map()));
+
+/**
+ * Get all language dependencies for a Prism given language.
+ *
+ * @param {string} lang Prism language name to get dependencies for.
+ * @returns {string[]}
+ */
+const getDependencies = lang => {
+    if (!languages.has(lang)) throw new Error(`Unknown Prism language: ${lang}`);
+
+    const required = languagesData[lang].require || [];
+    const modify = languagesData[lang].modify || [];
+    const dependencies = [
+        ...(Array.isArray(required)
+            ? required
+            : [ required ]),
+        ...(Array.isArray(modify)
+            ? modify
+            : [ modify ]),
+    ];
+    return dedupe([
+        ...dependencies,
+        ...dependencies.map(dep => getDependencies(dep)).flat(),
+    ]);
+};
+
+/**
+ * Plugin to restrict the languages that are bundled for Prism.
+ *
+ * This plugin requires that Webpack is installed as a dependency with `ContextReplacementPlugin` available.
+ *
+ * @param {string[]} langs Prism languages to restrict to.
+ * @returns {import('webpack').Plugin}
+ */
+const restrictWebpack = langs => {
+    // Webpack is not a dependency, so we only load it here if the user uses this
+    // eslint-disable-next-line import/no-extraneous-dependencies
+    const { ContextReplacementPlugin } = require('webpack');
+
+    const withDependencies = dedupe(langs.map(lang => [ lang, ...getDependencies(lang) ]).flat());
+    return new ContextReplacementPlugin(
+        /@digitalocean[/\\]do-markdownit[/\\]vendor[/\\]prismjs[/\\]components$/,
+        new RegExp(`prism-(${[ 'core', ...withDependencies.map(dep => regexEscape(dep)) ].join('|')})\\.js$`),
+    );
+};
+
+module.exports = {
+    languages,
+    languageAliases,
+    getDependencies,
+    restrictWebpack,
+};