fix(@angular-devkit/schematics): fix generate mangling files containing wide characters

Executing a command like `ng generate component my-component` can sometimes lead to
mangled Angular module files when inserting the component into `declaration` and
adding the import. This happens if the file contains characters that are wider than
one byte e.g. a copyright sign or an umlaut. Today it is expected to be able to use
two byte long characters in code.

The `UpdateBuffer` class operates using Buffer objects which use byte arrays internally.
Using text node positions provided by the TypeScript library, these will not match up.
This change looks up the textual position inside the Buffer and uses the correct index.

Closes #7851, #7950

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

@@ -30,9 +30,9 @@ export class UpdateRecorderBase implements UpdateRecorder {
     if (c0 == 0xEF && c1 == 0xBB && c2 == 0xBF) {
       return new UpdateRecorderBom(entry);
     } else if (c0 === 0xFF && c1 == 0xFE) {
-      return new UpdateRecorderBom(entry, 2);
+      return new UpdateRecorderBom(entry);
     } else if (c0 === 0xFE && c1 == 0xFF) {
-      return new UpdateRecorderBom(entry, 2);
+      return new UpdateRecorderBom(entry);
     }
 
     return new UpdateRecorderBase(entry);
@@ -70,7 +70,7 @@ export class UpdateRecorderBase implements UpdateRecorder {
 
 
 export class UpdateRecorderBom extends UpdateRecorderBase {
-  constructor(entry: FileEntry, private _delta = 3) {
+  constructor(entry: FileEntry, private _delta = 1) {
     super(entry);
   }
 

packages/angular_devkit/schematics/src/utility/update-buffer.ts

@@ -201,19 +201,31 @@ export class UpdateBuffer {
   }
 
   protected _slice(start: number): [Chunk, Chunk] {
-    this._assertIndex(start);
+    // If start is longer than the content, use start, otherwise determine exact position in string.
+    const index = start >= this._originalContent.length ? start : this._getTextPosition(start);
+
+    this._assertIndex(index);
 
     // Find the chunk by going through the list.
-    const h = this._linkedList.find(chunk => start <= chunk.end);
+    const h = this._linkedList.find(chunk => index <= chunk.end);
     if (!h) {
       throw Error('Chunk cannot be found.');
     }
 
-    if (start == h.end && h.next !== null) {
+    if (index == h.end && h.next !== null) {
       return [h, h.next];
     }
 
-    return [h, h.slice(start)];
+    return [h, h.slice(index)];
+  }
+
+  /**
+   * Gets the position in the content based on the position in the string.
+   * Some characters might be wider than one byte, thus we have to determine the position using
+   * string functions.
+   */
+  protected _getTextPosition(index: number): number {
+    return Buffer.from(this._originalContent.toString().substring(0, index)).length;
   }
 
   get length(): number {

packages/angular_devkit/schematics/src/utility/update-buffer_spec.ts

@@ -58,6 +58,16 @@ describe('UpdateBuffer', () => {
       mb.insertLeft(6, Buffer.from('Awesome '));
       expect(mb.toString()).toBe('Hello Great Awesome Beautiful World');
     });
+
+    it('works with special characters', () => {
+      const mb = new UpdateBuffer(Buffer.from('Ülaut'));
+
+      mb.insertLeft(1, Buffer.from('m'));
+      expect(mb.toString()).toBe('Ümlaut');
+
+      mb.insertLeft(0, Buffer.from('Hello '));
+      expect(mb.toString()).toBe('Hello Ümlaut');
+    });
   });
 
   describe('delete', () => {