chushihua

node_modules/babel-loader/lib/fs-cache.js

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+"use strict";
+
+/**
+ * Filesystem cache
+ *
+ * Given a file and a transform function, cache the result into files
+ * or retrieve the previously cached files if the given file is already known.
+ *
+ * @see https://github.com/babel/babel-loader/issues/34
+ * @see https://github.com/babel/babel-loader/pull/41
+ */
+var crypto = require("crypto");
+var mkdirp = require("mkdirp");
+var findCacheDir = require("find-cache-dir");
+var fs = require("fs");
+var os = require("os");
+var path = require("path");
+var zlib = require("zlib");
+
+var defaultCacheDirectory = null; // Lazily instantiated when needed
+
+/**
+ * Read the contents from the compressed file.
+ *
+ * @async
+ * @params {String} filename
+ * @params {Function} callback
+ */
+var read = function read(filename, callback) {
+  return fs.readFile(filename, function (err, data) {
+    if (err) return callback(err);
+
+    return zlib.gunzip(data, function (err, content) {
+      if (err) return callback(err);
+
+      var result = {};
+
+      try {
+        result = JSON.parse(content);
+      } catch (e) {
+        return callback(e);
+      }
+
+      return callback(null, result);
+    });
+  });
+};
+
+/**
+ * Write contents into a compressed file.
+ *
+ * @async
+ * @params {String} filename
+ * @params {String} result
+ * @params {Function} callback
+ */
+var write = function write(filename, result, callback) {
+  var content = JSON.stringify(result);
+
+  return zlib.gzip(content, function (err, data) {
+    if (err) return callback(err);
+
+    return fs.writeFile(filename, data, callback);
+  });
+};
+
+/**
+ * Build the filename for the cached file
+ *
+ * @params {String} source  File source code
+ * @params {Object} options Options used
+ *
+ * @return {String}
+ */
+var filename = function filename(source, identifier, options) {
+  var hash = crypto.createHash("md4");
+  var contents = JSON.stringify({
+    source: source,
+    options: options,
+    identifier: identifier
+  });
+
+  hash.update(contents);
+
+  return hash.digest("hex") + ".json.gz";
+};
+
+/**
+ * Handle the cache
+ *
+ * @params {String} directory
+ * @params {Object} params
+ * @params {Function} callback
+ */
+var handleCache = function handleCache(directory, params, callback) {
+  var source = params.source;
+  var options = params.options || {};
+  var transform = params.transform;
+  var identifier = params.identifier;
+  var shouldFallback = typeof params.directory !== "string" && directory !== os.tmpdir();
+
+  // Make sure the directory exists.
+  mkdirp(directory, function (err) {
+    // Fallback to tmpdir if node_modules folder not writable
+    if (err) return shouldFallback ? handleCache(os.tmpdir(), params, callback) : callback(err);
+
+    var file = path.join(directory, filename(source, identifier, options));
+
+    return read(file, function (err, content) {
+      var result = {};
+      // No errors mean that the file was previously cached
+      // we just need to return it
+      if (!err) return callback(null, content);
+
+      // Otherwise just transform the file
+      // return it to the user asap and write it in cache
+      try {
+        result = transform(source, options);
+      } catch (error) {
+        return callback(error);
+      }
+
+      return write(file, result, function (err) {
+        // Fallback to tmpdir if node_modules folder not writable
+        if (err) return shouldFallback ? handleCache(os.tmpdir(), params, callback) : callback(err);
+
+        callback(null, result);
+      });
+    });
+  });
+};
+
+/**
+ * Retrieve file from cache, or create a new one for future reads
+ *
+ * @async
+ * @param  {Object}   params
+ * @param  {String}   params.directory  Directory to store cached files
+ * @param  {String}   params.identifier Unique identifier to bust cache
+ * @param  {String}   params.source   Original contents of the file to be cached
+ * @param  {Object}   params.options  Options to be given to the transform fn
+ * @param  {Function} params.transform  Function that will transform the
+ *                                      original file and whose result will be
+ *                                      cached
+ *
+ * @param  {Function<err, result>} callback
+ *
+ * @example
+ *
+ *   cache({
+ *     directory: '.tmp/cache',
+ *     identifier: 'babel-loader-cachefile',
+ *     source: *source code from file*,
+ *     options: {
+ *       experimental: true,
+ *       runtime: true
+ *     },
+ *     transform: function(source, options) {
+ *       var content = *do what you need with the source*
+ *       return content;
+ *     }
+ *   }, function(err, result) {
+ *
+ *   });
+ */
+
+module.exports = function (params, callback) {
+  var directory = void 0;
+
+  if (typeof params.directory === "string") {
+    directory = params.directory;
+  } else {
+    if (defaultCacheDirectory === null) {
+      defaultCacheDirectory = findCacheDir({ name: "babel-loader" }) || os.tmpdir();
+    }
+    directory = defaultCacheDirectory;
+  }
+
+  handleCache(directory, params, callback);
+};