fix(@angular-devkit/schematics): add support for BOM to UpdateRecorder

Fixes angular/angular-cli#10644

packages/angular_devkit/schematics/src/tree/recorder.ts

@@ -21,6 +21,23 @@ export class UpdateRecorderBase implements UpdateRecorder {
     this._path = entry.path;
   }
 
+  static createFromFileEntry(entry: FileEntry): UpdateRecorderBase {
+    const c0 = entry.content.readUInt8(0, true);
+    const c1 = entry.content.readUInt8(1, true);
+    const c2 = entry.content.readUInt8(2, true);
+
+    // Check if we're BOM.
+    if (c0 == 0xEF && c1 == 0xBB && c2 == 0xBF) {
+      return new UpdateRecorderBom(entry);
+    } else if (c0 === 0xFF && c1 == 0xFE) {
+      return new UpdateRecorderBom(entry, 2);
+    } else if (c0 === 0xFE && c1 == 0xFF) {
+      return new UpdateRecorderBom(entry, 2);
+    }
+
+    return new UpdateRecorderBase(entry);
+  }
+
   get path() { return this._path; }
 
   // These just record changes.
@@ -50,3 +67,22 @@ export class UpdateRecorderBase implements UpdateRecorder {
     return this._content.generate();
   }
 }
+
+
+export class UpdateRecorderBom extends UpdateRecorderBase {
+  constructor(entry: FileEntry, private _delta = 3) {
+    super(entry);
+  }
+
+  insertLeft(index: number, content: Buffer | string) {
+    return super.insertLeft(index + this._delta, content);
+  }
+
+  insertRight(index: number, content: Buffer | string) {
+    return super.insertRight(index + this._delta, content);
+  }
+
+  remove(index: number, length: number) {
+    return super.remove(index + this._delta, length);
+  }
+}

packages/angular_devkit/schematics/src/tree/recorder_spec.ts

@@ -0,0 +1,66 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+import { normalize } from '@angular-devkit/core';
+import { SimpleFileEntry } from './entry';
+import { UpdateRecorderBase, UpdateRecorderBom } from './recorder';
+
+describe('UpdateRecorderBase', () => {
+  it('works for simple files', () => {
+    const buffer = new Buffer('Hello World');
+    const entry = new SimpleFileEntry(normalize('/some/path'), buffer);
+
+    const recorder = new UpdateRecorderBase(entry);
+    recorder.insertLeft(5, ' beautiful');
+    const result = recorder.apply(buffer);
+    expect(result.toString()).toBe('Hello beautiful World');
+  });
+
+  it('works for simple files (2)', () => {
+    const buffer = new Buffer('Hello World');
+    const entry = new SimpleFileEntry(normalize('/some/path'), buffer);
+
+    const recorder = new UpdateRecorderBase(entry);
+    recorder.insertRight(5, ' beautiful');
+    const result = recorder.apply(buffer);
+    expect(result.toString()).toBe('Hello beautiful World');
+  });
+
+  it('can create the proper recorder', () => {
+    const e = new SimpleFileEntry(normalize('/some/path'),  new Buffer('hello'));
+    expect(UpdateRecorderBase.createFromFileEntry(e) instanceof UpdateRecorderBase).toBe(true);
+    expect(UpdateRecorderBase.createFromFileEntry(e) instanceof UpdateRecorderBom).toBe(false);
+  });
+
+  it('can create the proper recorder (bom)', () => {
+    const eBom = new SimpleFileEntry(normalize('/some/path'), new Buffer('\uFEFFhello'));
+    expect(UpdateRecorderBase.createFromFileEntry(eBom) instanceof UpdateRecorderBase).toBe(true);
+    expect(UpdateRecorderBase.createFromFileEntry(eBom) instanceof UpdateRecorderBom).toBe(true);
+  });
+
+  it('supports empty files', () => {
+    const e = new SimpleFileEntry(normalize('/some/path'),  new Buffer(''));
+    expect(UpdateRecorderBase.createFromFileEntry(e) instanceof UpdateRecorderBase).toBe(true);
+  });
+
+  it('supports empty files (bom)', () => {
+    const eBom = new SimpleFileEntry(normalize('/some/path'), new Buffer('\uFEFF'));
+    expect(UpdateRecorderBase.createFromFileEntry(eBom) instanceof UpdateRecorderBase).toBe(true);
+  });
+});
+
+describe('UpdateRecorderBom', () => {
+  it('works for simple files', () => {
+    const buffer = new Buffer('\uFEFFHello World');
+    const entry = new SimpleFileEntry(normalize('/some/path'), buffer);
+
+    const recorder = new UpdateRecorderBom(entry);
+    recorder.insertLeft(5, ' beautiful');
+    const result = recorder.apply(buffer);
+    expect(result.toString()).toBe('\uFEFFHello beautiful World');
+  });
+});

packages/angular_devkit/schematics/src/tree/virtual.ts

@@ -186,7 +186,7 @@ export class VirtualTree implements Tree {
       throw new FileDoesNotExistException(path);
     }
 
-    return new UpdateRecorderBase(entry);
+    return UpdateRecorderBase.createFromFileEntry(entry);
   }
 
   commitUpdate(record: UpdateRecorder) {