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node_modules/sass-loader/lib/loader.js 4.64 KB
aaac7fed   liuqimichale   add
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  "use strict";
  
  const path = require("path");
  const async = require("neo-async");
  const formatSassError = require("./formatSassError");
  const webpackImporter = require("./webpackImporter");
  const normalizeOptions = require("./normalizeOptions");
  const pify = require("pify");
  const semver = require("semver");
  
  let nodeSassJobQueue = null;
  
  /**
   * The sass-loader makes node-sass available to webpack modules.
   *
   * @this {LoaderContext}
   * @param {string} content
   */
  function sassLoader(content) {
      const callback = this.async();
      const isSync = typeof callback !== "function";
      const self = this;
      const resourcePath = this.resourcePath;
  
      function addNormalizedDependency(file) {
          // node-sass returns POSIX paths
          self.dependency(path.normalize(file));
      }
  
      if (isSync) {
          throw new Error("Synchronous compilation is not supported anymore. See https://github.com/webpack-contrib/sass-loader/issues/333");
      }
  
      const options = normalizeOptions(this, content, webpackImporter(
          resourcePath,
          pify(this.resolve.bind(this)),
          addNormalizedDependency
      ));
  
      // Skip empty files, otherwise it will stop webpack, see issue #21
      if (options.data.trim() === "") {
          callback(null, "");
          return;
      }
  
      const render = getRenderFuncFromSassImpl(options.implementation || require("node-sass"));
  
      render(options, (err, result) => {
          if (err) {
              formatSassError(err, this.resourcePath);
              err.file && this.dependency(err.file);
              callback(err);
              return;
          }
  
          if (result.map && result.map !== "{}") {
              result.map = JSON.parse(result.map);
              // result.map.file is an optional property that provides the output filename.
              // Since we don't know the final filename in the webpack build chain yet, it makes no sense to have it.
              delete result.map.file;
              // The first source is 'stdin' according to node-sass because we've used the data input.
              // Now let's override that value with the correct relative path.
              // Since we specified options.sourceMap = path.join(process.cwd(), "/sass.map"); in normalizeOptions,
              // we know that this path is relative to process.cwd(). This is how node-sass works.
              result.map.sources[0] = path.relative(process.cwd(), resourcePath);
              // node-sass returns POSIX paths, that's why we need to transform them back to native paths.
              // This fixes an error on windows where the source-map module cannot resolve the source maps.
              // @see https://github.com/webpack-contrib/sass-loader/issues/366#issuecomment-279460722
              result.map.sourceRoot = path.normalize(result.map.sourceRoot);
              result.map.sources = result.map.sources.map(path.normalize);
          } else {
              result.map = null;
          }
  
          result.stats.includedFiles.forEach(addNormalizedDependency);
          callback(null, result.css.toString(), result.map);
      });
  }
  
  /**
   * Verifies that the implementation and version of Sass is supported by this loader.
   *
   * @param {Object} module
   * @returns {Function}
   */
  function getRenderFuncFromSassImpl(module) {
      const info = module.info;
      const components = info.split("\t");
  
      if (components.length < 2) {
          throw new Error("Unknown Sass implementation \"" + info + "\".");
      }
  
      const implementation = components[0];
      const version = components[1];
  
      if (!semver.valid(version)) {
          throw new Error("Invalid Sass version \"" + version + "\".");
      }
  
      if (implementation === "dart-sass") {
          if (!semver.satisfies(version, "^1.3.0")) {
              throw new Error("Dart Sass version " + version + " is incompatible with ^1.3.0.");
          }
          return module.render.bind(module);
      } else if (implementation === "node-sass") {
          if (!semver.satisfies(version, "^4.0.0")) {
              throw new Error("Node Sass version " + version + " is incompatible with ^4.0.0.");
          }
          // There is an issue with node-sass when async custom importers are used
          // See https://github.com/sass/node-sass/issues/857#issuecomment-93594360
          // We need to use a job queue to make sure that one thread is always available to the UV lib
          if (nodeSassJobQueue === null) {
              const threadPoolSize = Number(process.env.UV_THREADPOOL_SIZE || 4);
  
              nodeSassJobQueue = async.queue(module.render.bind(module), threadPoolSize - 1);
          }
  
          return nodeSassJobQueue.push.bind(nodeSassJobQueue);
      }
      throw new Error("Unknown Sass implementation \"" + implementation + "\".");
  }
  
  module.exports = sassLoader;