[FIX] Prevent FS write from draining Resources content

Previously, when writing to an FS-Adapter, a Resources content stream
would be drained, making it impossible to access a Resources content
again.

With this change, a Resources content will be buffered while draining
its content stream. An optional 'final' parameter can be supplied to
skip buffering to lower the memory demand of the operation.

Also add a pessimistic check for drained content streams.

lib/AbstractReaderWriter.js

@@ -21,10 +21,13 @@ class AbstractReaderWriter extends AbstractReader {
 	 * Writes the content of a resource to a path.
 	 *
 	 * @param {Resource} resource The Resource to write
+	 * @param {Object} [options]
+	 * @param {boolean} [options.final=false] Keep set to false if the resource should still have
+												access to its content after the write process
 	 * @returns {Promise<undefined>} Promise resolving once data has been written
 	 */
-	write(resource) {
-		return this._write(resource);
+	write(resource, options = {final: false}) {
+		return this._write(resource, options);
 	}
 
 	/**
@@ -33,9 +36,12 @@ class AbstractReaderWriter extends AbstractReader {
 	 * @abstract
 	 * @protected
 	 * @param {Resource} resource The Resource to write
+	 * @param {Object} [options]
+	 * @param {boolean} [options.final] Set to false if the resource should still have
+										access to its content after the write process
 	 * @returns {Promise<undefined>} Promise resolving once data has been written
 	 */
-	_write(resource) {
+	_write(resource, options) {
 		throw new Error("Not implemented");
 	}
 }

lib/Resource.js

@@ -95,6 +95,7 @@ class Resource {
 		// }
 		this._stream = null;
 		this._buffer = buffer;
+		this._contentDrained = false;
 	}
 
 	/**
@@ -144,6 +145,7 @@ class Resource {
 		// 	this._stream.destroy();
 		// }
 		this._stream = stream;
+		this._contentDrained = false;
 	}
 
 	/**
@@ -245,6 +247,11 @@ class Resource {
 		if (this._createStream) {
 			return this._createStream();
 		}
+		if (this._contentDrained) {
+			throw new Error(`Content stream of Resource ${this._path} has been drained. ` +
+							"This might be caused by accessing an already (finally) written resource.");
+		}
+		this._contentDrained = true;
 		return this._stream;
 	}
 
@@ -256,8 +263,8 @@ class Resource {
 	 */
 	_getBufferFromStream() {
 		return new Promise((resolve, reject) => {
-			let contentStream = this._getStream();
-			let buffers = [];
+			const contentStream = this._getStream();
+			const buffers = [];
 			contentStream.on("data", (data) => {
 				buffers.push(data);
 			});

lib/adapters/FileSystem.js

@@ -5,6 +5,7 @@ const glob = require("globby");
 const defaults = require("defaults");
 const clone = require("clone");
 const makeDir = require("make-dir");
+const {PassThrough} = require("stream");
 const Resource = require("../Resource");
 const AbstractAdapter = require("./AbstractAdapter");
 
@@ -167,9 +168,11 @@ class FileSystem extends AbstractAdapter {
 	 *
 	 * @private
 	 * @param {Resource} resource The Resource
+	 * @param {Object} options
+	 * @param {boolean} options.final Whether this resource can loose access to its content in the write process
 	 * @returns {Promise<undefined>} Promise resolving once data has been written
 	 */
-	_write(resource) {
+	_write(resource, {final}) {
 		const relPath = resource.getPath().substr(this._virBasePath.length);
 		const fsPath = path.join(this._fsBasePath, relPath);
 		const dirPath = path.dirname(fsPath);
@@ -180,10 +183,30 @@ class FileSystem extends AbstractAdapter {
 			fs
 		}).then(() => {
 			return new Promise((resolve, reject) => {
-				let contentStream = resource.getStream();
-				contentStream.on("error", function(err) {
-					reject(err);
-				});
+				let contentStream;
+				if (final) {
+					contentStream = resource.getStream();
+
+					contentStream.on("error", function(err) {
+						reject(err);
+					});
+				} else {
+					contentStream = new PassThrough();
+					const buffers = [];
+					contentStream.on("error", (err) => {
+						reject(err);
+					});
+					contentStream.on("data", (data) => {
+						buffers.push(data);
+					});
+					contentStream.on("end", () => {
+						let buffer = Buffer.concat(buffers);
+						resource.setBuffer(buffer);
+					});
+					resource.getStream().pipe(contentStream);
+				}
+
+
 				let write = fs.createWriteStream(fsPath);
 				write.on("error", function(err) {
 					reject(err);

test/lib/resources.js

@@ -40,23 +40,23 @@ test("Get resource from application.a (/index.html) and write it to /dest/ using
 		}));
 });
 
-test("FS RL: GLOB resources from application.a w/ virtual base path prefix", (t) => {
+test("FS-Adapter: GLOB resources from application.a w/ virtual base path prefix", (t) => {
 	let readerWriters = t.context.readerWriters;
 	// Get resource from one readerWriter
 	return t.notThrows(readerWriters.source.byGlob("/app/**/*.html").then(function(resources) {
 		t.deepEqual(resources.length, 1, "Found exactly one resource");
 	}));
 });
 
-test("FS RL: GLOB resources from application.a w/o virtual base path prefix", (t) => {
+test("FS-Adapter: GLOB resources from application.a w/o virtual base path prefix", (t) => {
 	let readerWriters = t.context.readerWriters;
 	// Get resource from one readerWriter
 	return t.notThrows(readerWriters.source.byGlob("/**/*.html").then(function(resources) {
 		t.deepEqual(resources.length, 1, "Found exactly one resource");
 	}));
 });
 
-test("Virtual RL: GLOB resources from application.a w/ virtual base path prefix", (t) => {
+test("Mem-Adapter: GLOB resources from application.a w/ virtual base path prefix", (t) => {
 	let readerWriter = ui5Fs.resourceFactory.createAdapter({
 		virBasePath: "/app/"
 	});
@@ -75,7 +75,7 @@ test("Virtual RL: GLOB resources from application.a w/ virtual base path prefix"
 	);
 });
 
-test("Virtual RL: GLOB resources from application.a w/o virtual base path prefix", (t) => {
+test("Mem-Adapter: GLOB resources from application.a w/o virtual base path prefix", (t) => {
 	let readerWriter = ui5Fs.resourceFactory.createAdapter({
 		virBasePath: "/app/"
 	});
@@ -94,8 +94,8 @@ test("Virtual RL: GLOB resources from application.a w/o virtual base path prefix
 	);
 });
 
-test("Virtual RL: GLOB virtual directory w/o virtual base path prefix", (t) => {
-	// TODO: Add similar test (globbing on empty directory) for FS RL
+test("Mem-Adapter: GLOB virtual directory w/o virtual base path prefix", (t) => {
+	// TODO: Add similar test (globbing on empty directory) for FS-Adapter
 	// TODO: Also add tests for nodir: true option
 	let readerWriter = ui5Fs.resourceFactory.createAdapter({
 		virBasePath: "/app/"