Updated the project.

my-app/node_modules/@angular-devkit/schematics/src/tree/host-tree.js

@@ -227,7 +227,10 @@ class HostTree {
             return decoder.decode(data);
         }
         catch (e) {
-            if (e instanceof TypeError) {
+            // The second part should not be needed. But Jest does not support instanceof correctly.
+            // See: https://github.com/jestjs/jest/issues/2549
+            if (e instanceof TypeError ||
+                e.code === 'ERR_ENCODING_INVALID_ENCODED_DATA') {
                 throw new Error(`Failed to decode "${path}" as UTF-8 text.`);
             }
             throw e;

my-app/node_modules/@angular-devkit/schematics/src/tree/interface.d.ts

@@ -75,6 +75,10 @@ export interface Tree {
     apply(action: Action, strategy?: MergeStrategy): void;
     readonly actions: Action[];
 }
+export interface TreeConstructor {
+    isTree(maybeTree: object): maybeTree is Tree;
+}
+export declare const Tree: TreeConstructor;
 export interface UpdateRecorder {
     insertLeft(index: number, content: Buffer | string): UpdateRecorder;
     insertRight(index: number, content: Buffer | string): UpdateRecorder;

my-app/node_modules/@angular-devkit/schematics/src/tree/interface.js

@@ -7,7 +7,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 Object.defineProperty(exports, "__esModule", { value: true });
-exports.TreeSymbol = exports.FileVisitorCancelToken = exports.MergeStrategy = void 0;
+exports.Tree = exports.TreeSymbol = exports.FileVisitorCancelToken = exports.MergeStrategy = void 0;
 var MergeStrategy;
 (function (MergeStrategy) {
     MergeStrategy[MergeStrategy["AllowOverwriteConflict"] = 2] = "AllowOverwriteConflict";
@@ -37,11 +37,8 @@ exports.TreeSymbol = (function () {
     }
     return globalSymbol.schematicTree;
 })();
-// eslint-disable-next-line @typescript-eslint/no-namespace
-var Tree;
-(function (Tree) {
-    function isTree(maybeTree) {
+exports.Tree = Object.freeze({
+    isTree(maybeTree) {
         return exports.TreeSymbol in maybeTree;
-    }
-    Tree.isTree = isTree;
-})(Tree || (Tree = {}));
+    },
+});

my-app/node_modules/@angular-devkit/schematics/src/tree/recorder.d.ts

@@ -5,24 +5,23 @@
  * 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 { UpdateBufferBase } from '../utility/update-buffer';
+import { BaseException } from '@angular-devkit/core';
+import MagicString from 'magic-string';
 import { FileEntry, UpdateRecorder } from './interface';
+export declare class IndexOutOfBoundException extends BaseException {
+    constructor(index: number, min: number, max?: number);
+}
 export declare class UpdateRecorderBase implements UpdateRecorder {
+    private readonly data;
+    private readonly bom;
     protected _path: string;
-    protected _original: Buffer;
-    protected _content: UpdateBufferBase;
-    constructor(entry: FileEntry);
+    protected content: MagicString;
+    constructor(data: Uint8Array, path: string, encoding?: string, bom?: boolean);
     static createFromFileEntry(entry: FileEntry): UpdateRecorderBase;
     get path(): string;
+    protected _assertIndex(index: number): void;
     insertLeft(index: number, content: Buffer | string): UpdateRecorder;
     insertRight(index: number, content: Buffer | string): UpdateRecorder;
     remove(index: number, length: number): UpdateRecorder;
     apply(content: Buffer): Buffer;
 }
-export declare class UpdateRecorderBom extends UpdateRecorderBase {
-    private _delta;
-    constructor(entry: FileEntry, _delta?: number);
-    insertLeft(index: number, content: Buffer | string): UpdateRecorder;
-    insertRight(index: number, content: Buffer | string): UpdateRecorder;
-    remove(index: number, length: number): UpdateRecorder;
-}

my-app/node_modules/@angular-devkit/schematics/src/tree/recorder.js

@@ -6,18 +6,40 @@
  * 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
  */
+var __importDefault = (this && this.__importDefault) || function (mod) {
+    return (mod && mod.__esModule) ? mod : { "default": mod };
+};
 Object.defineProperty(exports, "__esModule", { value: true });
-exports.UpdateRecorderBom = exports.UpdateRecorderBase = void 0;
+exports.UpdateRecorderBase = exports.IndexOutOfBoundException = void 0;
+const core_1 = require("@angular-devkit/core");
+const magic_string_1 = __importDefault(require("magic-string"));
 const exception_1 = require("../exception/exception");
-const update_buffer_1 = require("../utility/update-buffer");
+class IndexOutOfBoundException extends core_1.BaseException {
+    constructor(index, min, max = Infinity) {
+        super(`Index ${index} outside of range [${min}, ${max}].`);
+    }
+}
+exports.IndexOutOfBoundException = IndexOutOfBoundException;
 class UpdateRecorderBase {
+    data;
+    bom;
     _path;
-    _original;
-    _content;
-    constructor(entry) {
-        this._original = Buffer.from(entry.content);
-        this._content = update_buffer_1.UpdateBufferBase.create(entry.path, entry.content);
-        this._path = entry.path;
+    content;
+    constructor(data, path, encoding = 'utf-8', bom = false) {
+        this.data = data;
+        this.bom = bom;
+        let text;
+        try {
+            text = new TextDecoder(encoding, { fatal: true, ignoreBOM: false }).decode(data);
+        }
+        catch (e) {
+            if (e instanceof TypeError) {
+                throw new Error(`Failed to decode "${path}" as ${encoding} text.`);
+            }
+            throw e;
+        }
+        this._path = path;
+        this.content = new magic_string_1.default(text);
     }
     static createFromFileEntry(entry) {
         const c0 = entry.content.byteLength > 0 && entry.content.readUInt8(0);
@@ -25,54 +47,47 @@ class UpdateRecorderBase {
         const c2 = entry.content.byteLength > 2 && entry.content.readUInt8(2);
         // Check if we're BOM.
         if (c0 == 0xef && c1 == 0xbb && c2 == 0xbf) {
-            return new UpdateRecorderBom(entry);
+            return new UpdateRecorderBase(entry.content, entry.path, 'utf-8', true);
         }
         else if (c0 === 0xff && c1 == 0xfe) {
-            return new UpdateRecorderBom(entry);
+            return new UpdateRecorderBase(entry.content, entry.path, 'utf-16le', true);
         }
         else if (c0 === 0xfe && c1 == 0xff) {
-            return new UpdateRecorderBom(entry);
+            return new UpdateRecorderBase(entry.content, entry.path, 'utf-16be', true);
         }
-        return new UpdateRecorderBase(entry);
+        return new UpdateRecorderBase(entry.content, entry.path);
     }
     get path() {
         return this._path;
     }
+    _assertIndex(index) {
+        if (index < 0 || index > this.content.original.length) {
+            throw new IndexOutOfBoundException(index, 0, this.content.original.length);
+        }
+    }
     // These just record changes.
     insertLeft(index, content) {
-        this._content.insertLeft(index, typeof content == 'string' ? Buffer.from(content) : content);
+        this._assertIndex(index);
+        this.content.appendLeft(index, content.toString());
         return this;
     }
     insertRight(index, content) {
-        this._content.insertRight(index, typeof content == 'string' ? Buffer.from(content) : content);
+        this._assertIndex(index);
+        this.content.appendRight(index, content.toString());
         return this;
     }
     remove(index, length) {
-        this._content.remove(index, length);
+        this._assertIndex(index);
+        this.content.remove(index, index + length);
         return this;
     }
     apply(content) {
-        if (!content.equals(this._content.original)) {
+        if (!content.equals(this.data)) {
             throw new exception_1.ContentHasMutatedException(this.path);
         }
-        return this._content.generate();
+        // Schematics only support writing UTF-8 text
+        const result = Buffer.from((this.bom ? '\uFEFF' : '') + this.content.toString(), 'utf-8');
+        return result;
     }
 }
 exports.UpdateRecorderBase = UpdateRecorderBase;
-class UpdateRecorderBom extends UpdateRecorderBase {
-    _delta;
-    constructor(entry, _delta = 1) {
-        super(entry);
-        this._delta = _delta;
-    }
-    insertLeft(index, content) {
-        return super.insertLeft(index + this._delta, content);
-    }
-    insertRight(index, content) {
-        return super.insertRight(index + this._delta, content);
-    }
-    remove(index, length) {
-        return super.remove(index + this._delta, length);
-    }
-}
-exports.UpdateRecorderBom = UpdateRecorderBom;