Update VirtualModulesPlugin from upstream

This updates the internal VirtualModulesPlugin, which is copied from
https://github.com/sysgears/webpack-virtual-modules. I went through all
commits since this virtual.js was added, and applied them manually to
the svelte-loader version where applicable. These upstream changes
allow for using Webpack 5 with svelte-loader.

This also adds a LICENSE file to comply with the requirements of the MIT
license for the plugin files. The LICENSE file also adds in the text of
MIT license that svelte-loader is licensed under (with a different
copyright line, since svelte-loader wasn't written by SysGears)

LICENSE

@@ -0,0 +1,42 @@
+svelte-loader is licensed under the MIT license:
+Copyright (c) 2020 svelte-loader contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+lib/virtual.js and lib/virtual-stats.js also contain code licensed under the
+MIT license:
+Copyright (c) 2017 SysGears
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

index.js

@@ -178,6 +178,6 @@ module.exports = function(source, map) {
 	}, err => callback(err)).catch(err => {
 		// wrap error to provide correct
 		// context when logging to console
-		callback(new Error(`${err.name}: ${err.toString()}`));
+		callback(new Error(`${err.name || "Error"}: ${err.toString()}`));
 	});
 };

lib/virtual-stats.js

@@ -1,3 +1,5 @@
+// Adapted from https://github.com/sysgears/webpack-virtual-modules
+
 /**
  * Used to cache a stats object for the virtual file.
  * Extracted from the `mock-fs` package.

lib/virtual.js

@@ -1,9 +1,26 @@
+// Adapted from https://github.com/sysgears/webpack-virtual-modules
+
 var VirtualStats = require('./virtual-stats');
+var path = require("path");
 
 var inode = 45000000;
 
-// Adapted from https://github.com/sysgears/webpack-virtual-modules
-// MIT Licensed https://github.com/sysgears/webpack-virtual-modules/blob/master/LICENSE
+function createWebpackData(result) {
+	return (function(backendOrStorage) {
+		// In Webpack v5, this variable is a "Backend", and has the data stored in a field
+		// _data. In V4, the `_` prefix isn't present.
+		if (backendOrStorage._data) {
+			const curLevelIdx = backendOrStorage._currentLevel;
+			const curLevel = backendOrStorage._levels[curLevelIdx];
+			return {
+				result: this.result,
+				level: curLevel
+			};
+		}
+		// Webpack 4
+		return [null, result];
+	}).bind({ result: result });
+}
 
 /**
  * @param {Compiler} compiler - the webpack compiler
@@ -16,24 +33,69 @@ function VirtualModulesPlugin(compiler) {
 
 		compiler.inputFileSystem.purge = function() {
 			if (originalPurge) {
-				originalPurge.call(this, arguments);
+				originalPurge.apply(this, arguments);
 			}
 			if (this._virtualFiles) {
-				Object.keys(this._virtualFiles).forEach(
-					function(file) {
-						var data = this._virtualFiles[file];
-						setData(this._statStorage, file, [null, data.stats]);
-						setData(this._readFileStorage, file, [null, data.contents]);
-					}.bind(this)
-				);
+				Object.keys(this._virtualFiles).forEach(function(file) {
+					var data = this._virtualFiles[file];
+					this._writeVirtualFile(file, data.stats, data.contents);
+				}.bind(this));
 			}
 		};
 
 		compiler.inputFileSystem._writeVirtualFile = function(file, stats, contents) {
+			const statStorage = getStatStorage(this);
+			const fileStorage = getFileStorage(this);
+			const readDirStorage = getReadDirBackend(this);
 			this._virtualFiles = this._virtualFiles || {};
 			this._virtualFiles[file] = { stats: stats, contents: contents };
-			setData(this._statStorage, file, [null, stats]);
-			setData(this._readFileStorage, file, [null, contents]);
+			setData(statStorage, file, createWebpackData(stats));
+			setData(fileStorage, file, createWebpackData(contents));
+			var segments = file.split(/[\\/]/);
+			var count = segments.length - 1;
+			var minCount = segments[0] ? 1 : 0;
+			while (count > minCount) {
+				var dir = segments.slice(0, count).join(path.sep) || path.sep;
+				try {
+					compiler.inputFileSystem.readdirSync(dir);
+				} catch (e) {
+					var time = new Date();
+					var timeMs = time.getTime();
+					var dirStats = new VirtualStats({
+						dev: 8675309,
+						nlink: 0,
+						uid: 1000,
+						gid: 1000,
+						rdev: 0,
+						blksize: 4096,
+						ino: inode++,
+						mode: 16877,
+						size: stats.size,
+						blocks: Math.floor(stats.size / 4096),
+						atimeMs: timeMs,
+						mtimeMs: timeMs,
+						ctimeMs: timeMs,
+						birthtimeMs: timeMs,
+						atime: time,
+						mtime: time,
+						ctime: time,
+						birthtime: time
+					});
+					setData(readDirStorage, dir, createWebpackData([]));
+					setData(statStorage, dir, createWebpackData(dirStats));
+				}
+				var dirData = getData(getReadDirBackend(this), dir);
+				// Webpack v4 returns an array, webpack v5 returns an object
+				dirData = dirData[1] || dirData.result;
+				var filename = segments[count];
+				if (dirData.indexOf(filename) < 0) {
+					var files = dirData.concat([filename]).sort();
+					setData(getReadDirBackend(this), dir, createWebpackData(files));
+				} else {
+					break;
+				}
+				count--;
+			}
 		};
 	}
 
@@ -75,14 +137,81 @@ VirtualModulesPlugin.prototype.writeModule = function(filePath, contents) {
 		birthtime: time
 	});
 
+	// When using the WatchIgnorePlugin (https://github.com/webpack/webpack/blob/52184b897f40c75560b3630e43ca642fcac7e2cf/lib/WatchIgnorePlugin.js),
+	// the original watchFileSystem is stored in `wfs`. The following "unwraps" the ignoring
+	// wrappers, giving us access to the "real" watchFileSystem.
+	let finalWatchFileSystem = this._watcher && this._watcher.watchFileSystem;
+
+	while (finalWatchFileSystem && finalWatchFileSystem.wfs) {
+		finalWatchFileSystem = finalWatchFileSystem.wfs;
+	}
 	this.compiler.inputFileSystem._writeVirtualFile(filePath, stats, contents);
 };
 
-function setData(storage, key, value) {
-	if (storage.data instanceof Map) {
-		storage.data.set(key, value);
+function getData(storage, key) {
+	// Webpack 5
+	if (storage._data instanceof Map) {
+		return storage._data.get(key);
+	} else if (storage._data) {
+		return storage.data[key];
+	} else if (storage.data instanceof Map) {
+		// Webpack v4
+		return storage.data.get(key);
+	} else {
+		return storage.data[key];
+	}
+}
+
+function setData(backendOrStorage, key, valueFactory) {
+	const value = valueFactory(backendOrStorage);
+
+	// Webpack v5
+	if (backendOrStorage._data instanceof Map) {
+		backendOrStorage._data.set(key, value);
+	} else if (backendOrStorage._data) {
+		backendOrStorage.data[key] = value;
+	} else if (backendOrStorage.data instanceof Map) {
+		// Webpack 4
+		backendOrStorage.data.set(key, value);
+		backendOrStorage.data.set(key, value);
+	} else {
+		backendOrStorage.data[key] = value;
+		backendOrStorage.data[key] = value;
+	}
+}
+
+function getStatStorage(fileSystem) {
+	if (fileSystem._statStorage) {
+		// Webpack v4
+		return fileSystem._statStorage;
+	} else if (fileSystem._statBackend) {
+		// webpack v5
+		return fileSystem._statBackend;
+	} else {
+		// Unknown version?
+		throw new Error("Couldn't find a stat storage");
+	}
+}
+
+function getFileStorage(fileSystem) {
+	if (fileSystem._readFileStorage) {
+		// Webpack v4
+		return fileSystem._readFileStorage;
+	} else if (fileSystem._readFileBackend) {
+		// Webpack v5
+		return fileSystem._readFileBackend;
+	} else {
+		throw new Error("Couldn't find a readFileStorage");
+	}
+}
+
+function getReadDirBackend(fileSystem) {
+	if (fileSystem._readdirBackend) {
+		return fileSystem._readdirBackend;
+	} else if (fileSystem._readdirStorage) {
+		return fileSystem._readdirStorage;
 	} else {
-		storage.data[key] = value;
+		throw new Error("Couldn't find a readDirStorage from Webpack Internals");
 	}
 }