refactor(@schematics/angular): avoid InsertChange type assumptions

This change introduces a helper function (`applyToUpdateRecorder`) that handles all known `Change` classes.  The use of this helper function removes type assumptions within the schematics.  Many of these assumptions caused compilation errors when strict TypeScript options are enabled.

Author: clydin

packages/schematics/angular/app-shell/index.ts

@@ -26,7 +26,7 @@ import {
   insertImport,
   isImported,
 } from '../utility/ast-utils';
-import { Change, InsertChange } from '../utility/change';
+import { applyToUpdateRecorder } from '../utility/change';
 import { getAppModulePath } from '../utility/ng-ast-utils';
 import { targetBuildNotFoundError } from '../utility/project-targets';
 import { getWorkspace, updateWorkspace } from '../utility/workspace';
@@ -191,11 +191,7 @@ function addRouterModule(mainPath: string): Rule {
     const moduleSource = getSourceFile(host, modulePath);
     const changes = addImportToModule(moduleSource, modulePath, 'RouterModule', '@angular/router');
     const recorder = host.beginUpdate(modulePath);
-    changes.forEach((change: Change) => {
-      if (change instanceof InsertChange) {
-        recorder.insertLeft(change.pos, change.toAdd);
-      }
-    });
+    applyToUpdateRecorder(recorder, changes);
     host.commitUpdate(recorder);
 
     return host;
@@ -248,9 +244,9 @@ function addServerRoutes(options: AppShellOptions): Rule {
       const routesChange = insertImport(moduleSource,
                                         modulePath,
                                         'Routes',
-                                        '@angular/router') as InsertChange;
-      if (routesChange.toAdd) {
-        recorder.insertLeft(routesChange.pos, routesChange.toAdd);
+                                        '@angular/router');
+      if (routesChange) {
+        applyToUpdateRecorder(recorder, [routesChange]);
       }
 
       const imports = getSourceNodes(moduleSource)
@@ -269,18 +265,16 @@ function addServerRoutes(options: AppShellOptions): Rule {
       const routerModuleChange = insertImport(moduleSource,
                                               modulePath,
                                               'RouterModule',
-                                              '@angular/router') as InsertChange;
+                                              '@angular/router');
 
-      if (routerModuleChange.toAdd) {
-        recorder.insertLeft(routerModuleChange.pos, routerModuleChange.toAdd);
+      if (routerModuleChange) {
+        applyToUpdateRecorder(recorder, [routerModuleChange]);
       }
 
       const metadataChange = addSymbolToNgModuleMetadata(
           moduleSource, modulePath, 'imports', 'RouterModule.forRoot(routes)');
       if (metadataChange) {
-        metadataChange.forEach((change: InsertChange) => {
-          recorder.insertRight(change.pos, change.toAdd);
-        });
+        applyToUpdateRecorder(recorder, metadataChange);
       }
       host.commitUpdate(recorder);
     }

packages/schematics/angular/service-worker/index.ts

@@ -21,7 +21,7 @@ import {
 import { NodePackageInstallTask } from '@angular-devkit/schematics/tasks';
 import * as ts from '../third_party/github.com/Microsoft/TypeScript/lib/typescript';
 import { addSymbolToNgModuleMetadata, getEnvironmentExportName, insertImport, isImported } from '../utility/ast-utils';
-import { InsertChange } from '../utility/change';
+import { applyToUpdateRecorder } from '../utility/change';
 import { addPackageJsonDependency, getPackageJsonDependency } from '../utility/dependencies';
 import { getAppModulePath } from '../utility/ng-ast-utils';
 import { relativePathToWorkspaceRoot } from '../utility/paths';
@@ -63,7 +63,7 @@ function updateAppModule(mainPath: string): Rule {
       const change = insertImport(moduleSource, modulePath, importModule, importPath);
       if (change) {
         const recorder = host.beginUpdate(modulePath);
-        recorder.insertLeft((change as InsertChange).pos, (change as InsertChange).toAdd);
+        applyToUpdateRecorder(recorder, [change]);
         host.commitUpdate(recorder);
       }
     }
@@ -84,7 +84,7 @@ function updateAppModule(mainPath: string): Rule {
       const change = insertImport(moduleSource, modulePath, importModule, importPath);
       if (change) {
         const recorder = host.beginUpdate(modulePath);
-        recorder.insertLeft((change as InsertChange).pos, (change as InsertChange).toAdd);
+        applyToUpdateRecorder(recorder, [change]);
         host.commitUpdate(recorder);
       }
     }
@@ -97,9 +97,7 @@ function updateAppModule(mainPath: string): Rule {
       moduleSource, modulePath, 'imports', importText);
     if (metadataChanges) {
       const recorder = host.beginUpdate(modulePath);
-      metadataChanges.forEach((change: InsertChange) => {
-        recorder.insertRight(change.pos, change.toAdd);
-      });
+      applyToUpdateRecorder(recorder, metadataChanges);
       host.commitUpdate(recorder);
     }
 

packages/schematics/angular/utility/change.ts

@@ -5,6 +5,8 @@
  * 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 { UpdateRecorder } from '@angular-devkit/schematics';
+
 export interface Host {
   write(path: string, content: string): Promise<void>;
   read(path: string): Promise<string>;
@@ -75,7 +77,7 @@ export class RemoveChange implements Change {
   order: number;
   description: string;
 
-  constructor(public path: string, private pos: number, private toRemove: string) {
+  constructor(public path: string, private pos: number, public toRemove: string) {
     if (pos < 0) {
       throw new Error('Negative positions are invalid');
     }
@@ -101,8 +103,8 @@ export class ReplaceChange implements Change {
   order: number;
   description: string;
 
-  constructor(public path: string, private pos: number, private oldText: string,
-              private newText: string) {
+  constructor(public path: string, private pos: number, public oldText: string,
+              public newText: string) {
     if (pos < 0) {
       throw new Error('Negative positions are invalid');
     }
@@ -125,3 +127,18 @@ export class ReplaceChange implements Change {
     });
   }
 }
+
+export function applyToUpdateRecorder(recorder: UpdateRecorder, changes: Change[]): void {
+  for (const change of changes) {
+    if (change instanceof InsertChange) {
+      recorder.insertLeft(change.pos, change.toAdd);
+    } else if (change instanceof RemoveChange) {
+      recorder.remove(change.order, change.toRemove.length);
+    } else if (change instanceof ReplaceChange) {
+      recorder.remove(change.order, change.oldText.length);
+      recorder.insertLeft(change.order, change.newText);
+    } else if (!(change instanceof NoopChange)) {
+      throw new Error('Unknown Change type encountered when updating a recorder.');
+    }
+  }
+}