Virtual FS without exposing separate plugin

.eslintrc

@@ -18,6 +18,7 @@
     "mocha"
   ],
   "env": {
-    "node": true
+    "node": true,
+    "es6": true
   }
 }

index.js

@@ -1,17 +1,14 @@
-const { basename, extname, posix, relative } = require('path');
+const { basename, extname, relative } = require('path');
 const { compile, preprocess } = require('svelte');
 const { getOptions } = require('loader-utils');
-const { statSync, utimesSync, writeFileSync } = require('fs');
-const { tmpdir } = require('os');
+const VirtualModules = require('./lib/virtual');
 
 const hotApi = require.resolve('./lib/hot-api.js');
 
 function makeHot(id, code, hotOptions) {
 	const options = JSON.stringify(hotOptions);
 	const replacement = `
-
 if (module.hot) {
-
 	const { configure, register, reload } = require('${posixify(hotApi)}');
 
 	module.hot.accept();
@@ -26,7 +23,6 @@ if (module.hot) {
 	}
 }
 
-
 export default $2;
 `;
 
@@ -80,7 +76,15 @@ function deprecatePreprocessOptions(options) {
 	options.preprocess = options.preprocess || preprocessOptions;
 }
 
+const virtualModuleInstances = new Map();
+
 module.exports = function(source, map) {
+	if (this._compiler && !virtualModuleInstances.has(this._compiler)) {
+		virtualModuleInstances.set(this._compiler, new VirtualModules(this._compiler));
+	}
+
+	const virtualModules = virtualModuleInstances.get(this._compiler);
+
 	this.cacheable();
 
 	const options = Object.assign({}, this.options, getOptions(this));
@@ -90,47 +94,41 @@ module.exports = function(source, map) {
 	const isProduction = this.minimize || process.env.NODE_ENV === 'production';
 
 	options.filename = this.resourcePath;
-	if (!options.format) {
-		options.format = this.version === 1 ? options.format || 'cjs' : 'es';
-	}
-	if (!options.shared) {
-		options.shared = options.format === 'es' && 'svelte/shared.js';
-	}
-
+	if (!('format' in options)) options.format = 'es';
+	if (!('shared' in options)) options.shared = options.format === 'es' && 'svelte/shared.js';
+	if (!('name' in options)) options.name = capitalize(sanitize(options.filename));
+	if (!('onwarn' in options)) options.onwarn = warning => this.emitWarning(new Error(warning));
 	if (options.emitCss) options.css = false;
 
-	if (!options.name) options.name = capitalize(sanitize(options.filename));
-
-	if (!options.onwarn) options.onwarn = warning => this.emitWarning(new Error(warning));
-
 	deprecatePreprocessOptions(options);
 	options.preprocess.filename = options.filename;
 
 	preprocess(source, options.preprocess).then(processed => {
-		let { js, css, ast } = normalize(compile(processed.toString(), options));
-
-		if (options.emitCss && css.code) {
-			const posixTmpdir = posixify(tmpdir());
-			const tmpFile = posix.join(posixTmpdir, 'svelte-' + ast.hash + '.css');
-
-			css.code += '\n/*# sourceMappingURL=' + css.map.toUrl() + '*/';
-			js.code = js.code + `\nrequire('${tmpFile}');\n`;
-
-			writeFileSync(tmpFile, css.code);
-			const { atime, mtime } = statSync(tmpFile);
-			utimesSync(tmpFile, new Date(atime.getTime() - 99999), new Date(mtime.getTime() - 99999));
-		}
+		let { js, css } = normalize(compile(processed.toString(), options));
 
 		if (options.hotReload && !isProduction && !isServer) {
 			const hotOptions = Object.assign({}, options.hotOptions);
 			const id = JSON.stringify(relative(process.cwd(), options.filename));
 			js.code = makeHot(id, js.code, hotOptions);
 		}
 
+		if (options.emitCss && css.code) {
+			const cssFilepath = options.filename.replace(
+				/\.[^/.]+$/,
+				`.svelte.css`
+			);
+			css.code += '\n/*# sourceMappingURL=' + css.map.toUrl() + '*/';
+			js.code = js.code + `\nimport '${cssFilepath}';\n`;
+
+			if (virtualModules) {
+				virtualModules.writeModule(cssFilepath, css.code);
+			}
+		}
+
 		callback(null, js.code, js.map);
 	}, err => callback(err)).catch(err => {
 		// wrap error to provide correct
 		// context when logging to console
 		callback(new Error(`${err.name}: ${err.toString()}`));
 	});
-};
+};

lib/virtual-stats.js

@@ -0,0 +1,89 @@
+/**
+ * Used to cache a stats object for the virtual file.
+ * Extracted from the `mock-fs` package.
+ *
+ * @author Tim Schaub http://tschaub.net/
+ * @link https://github.com/tschaub/mock-fs/blob/master/lib/binding.js
+ * @link https://github.com/tschaub/mock-fs/blob/master/license.md
+ */
+
+/* eslint-disable no-restricted-syntax, no-prototype-builtins, no-continue */
+/* eslint-disable no-bitwise, no-underscore-dangle */
+
+'use strict';
+
+var constants = require('constants');
+
+/**
+ * Create a new stats object.
+ * @param {Object} config Stats properties.
+ * @constructor
+ */
+function VirtualStats(config) {
+	for (var key in config) {
+		if (!config.hasOwnProperty(key)) {
+			continue;
+		}
+		this[key] = config[key];
+	}
+}
+
+/**
+ * Check if mode indicates property.
+ * @param {number} property Property to check.
+ * @return {boolean} Property matches mode.
+ */
+VirtualStats.prototype._checkModeProperty = function(property) {
+	return (this.mode & constants.S_IFMT) === property;
+};
+
+/**
+ * @return {Boolean} Is a directory.
+ */
+VirtualStats.prototype.isDirectory = function() {
+	return this._checkModeProperty(constants.S_IFDIR);
+};
+
+/**
+ * @return {Boolean} Is a regular file.
+ */
+VirtualStats.prototype.isFile = function() {
+	return this._checkModeProperty(constants.S_IFREG);
+};
+
+/**
+ * @return {Boolean} Is a block device.
+ */
+VirtualStats.prototype.isBlockDevice = function() {
+	return this._checkModeProperty(constants.S_IFBLK);
+};
+
+/**
+ * @return {Boolean} Is a character device.
+ */
+VirtualStats.prototype.isCharacterDevice = function() {
+	return this._checkModeProperty(constants.S_IFCHR);
+};
+
+/**
+ * @return {Boolean} Is a symbolic link.
+ */
+VirtualStats.prototype.isSymbolicLink = function() {
+	return this._checkModeProperty(constants.S_IFLNK);
+};
+
+/**
+ * @return {Boolean} Is a named pipe.
+ */
+VirtualStats.prototype.isFIFO = function() {
+	return this._checkModeProperty(constants.S_IFIFO);
+};
+
+/**
+ * @return {Boolean} Is a socket.
+ */
+VirtualStats.prototype.isSocket = function() {
+	return this._checkModeProperty(constants.S_IFSOCK);
+};
+
+module.exports = VirtualStats;

lib/virtual.js

@@ -0,0 +1,73 @@
+var VirtualStats = require('./virtual-stats');
+
+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 VirtualModulesPlugin(compiler) {
+	this.compiler = compiler;
+
+	if (!compiler.inputFileSystem._writeVirtualFile) {
+		var originalPurge = compiler.inputFileSystem.purge;
+
+		compiler.inputFileSystem.purge = function() {
+			originalPurge.call(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)
+				);
+			}
+		};
+
+		compiler.inputFileSystem._writeVirtualFile = function(file, stats, contents) {
+			this._virtualFiles = this._virtualFiles || {};
+			this._virtualFiles[file] = { stats: stats, contents: contents };
+			setData(this._statStorage, file, [null, stats]);
+			setData(this._readFileStorage, file, [null, contents]);
+		};
+	}
+
+	compiler.hooks.watchRun.tapAsync('VirtualModulesPlugin', (watcher, callback) => {
+		this._watcher = watcher.compiler || watcher;
+		callback();
+	});
+}
+
+VirtualModulesPlugin.prototype.writeModule = function(filePath, contents) {
+	var len = contents ? contents.length : 0;
+	var time = Date.now();
+
+	var stats = new VirtualStats({
+		dev: 8675309,
+		nlink: 0,
+		uid: 1000,
+		gid: 1000,
+		rdev: 0,
+		blksize: 4096,
+		ino: inode++,
+		mode: 33188,
+		size: len,
+		blocks: Math.floor(len / 4096),
+		atime: time,
+		mtime: time,
+		ctime: time,
+		birthtime: time
+	});
+
+	this.compiler.inputFileSystem._writeVirtualFile(filePath, stats, contents);
+};
+
+function setData(storage, key, value) {
+	if (storage.data instanceof Map) {
+		storage.data.set(key, value);
+	} else {
+		storage.data[key] = value;
+	}
+}
+
+module.exports = VirtualModulesPlugin;