fix(ng-update): do not fail if @schematics/angular version is outdated (#13929)

* Currently the `ng update` could potentially fail if the version of `@schematics/angular` is outdated on the given project. We should avoid to depend on `@schematics/angular` for the `ng-update` schematic.
* No longer fails if the workspace configuration could not be found. It's very uncommon that someone tries to update a CLI project that still uses `.angular-cli.json` because:

     1) The CLI version for the project doesn't support `ng update` with custom downstream migrations
     2) In case the developer runs a different CLI version for _that_ outdated project, the CLI technically does run for an invalid project.

Even though, this is a rare case, it doesn't hurt not throwing if the workspace configuration couldn't be found when running `ng update`.

src/cdk/schematics/ng-update/upgrade-rules/project-tsconfig-paths.spec.ts

@@ -0,0 +1,59 @@
+import {HostTree} from '@angular-devkit/schematics';
+import {UnitTestTree} from '@angular-devkit/schematics/testing';
+import {getProjectTsConfigPaths} from './project-tsconfig-paths';
+
+describe('ng-update project-tsconfig-paths', () => {
+
+  let testTree: UnitTestTree;
+
+  beforeEach(() => {
+    testTree = new UnitTestTree(new HostTree());
+  });
+
+  it('should detect build tsconfig path inside of angular.json file', () => {
+    testTree.create('/my-custom-config.json', '');
+    testTree.create('/angular.json', JSON.stringify({
+      projects: {
+        my_name: {
+          architect: {
+            build: {
+              options: {
+                tsConfig: './my-custom-config.json'
+              }
+            }
+          }
+        }
+      }
+    }));
+
+    expect(getProjectTsConfigPaths(testTree)).toEqual(['./my-custom-config.json']);
+  });
+
+  it('should detect test tsconfig path inside of .angular.json file', () => {
+    testTree.create('/my-test-config.json', '');
+    testTree.create('/.angular.json', JSON.stringify({
+      projects: {
+        with_tests: {
+          architect: {
+            test: {
+              options: {
+                tsConfig: './my-test-config.json'
+              }
+            }
+          }
+        }
+      }
+    }));
+
+    expect(getProjectTsConfigPaths(testTree)).toEqual(['./my-test-config.json']);
+  });
+
+  it('should detect common tsconfigs if no workspace config could be found', () => {
+    testTree.create('/tsconfig.json', '');
+    testTree.create('/src/tsconfig.json', '');
+    testTree.create('/src/tsconfig.app.json', '');
+
+    expect(getProjectTsConfigPaths(testTree))
+      .toEqual(['./tsconfig.json', './src/tsconfig.json', './src/tsconfig.app.json']);
+  });
+});

src/cdk/schematics/ng-update/upgrade-rules/project-tsconfig-paths.ts

@@ -7,7 +7,6 @@
  */
 
 import {Tree} from '@angular-devkit/schematics';
-import {getWorkspace} from '@schematics/angular/utility/config';
 
 /**
  * Gets all tsconfig paths from a CLI project by reading the workspace configuration
@@ -22,26 +21,52 @@ export function getProjectTsConfigPaths(tree: Tree): string[] {
   ]);
 
   // Add any tsconfig directly referenced in a build or test task of the angular.json workspace.
-  const workspace = getWorkspace(tree);
+  const workspace = getWorkspaceConfigGracefully(tree);
 
-  for (const project of Object.values(workspace.projects)) {
-    ['build', 'test'].forEach(targetName => {
-      if (project.targets &&
-          project.targets[targetName] &&
-          project.targets[targetName].options &&
-          project.targets[targetName].options.tsConfig) {
-        tsconfigPaths.add(project.targets[targetName].options.tsConfig);
-      }
+  if (workspace) {
+    for (const project of Object.values<any>(workspace.projects)) {
+      ['build', 'test'].forEach(targetName => {
+        if (project.targets &&
+            project.targets[targetName] &&
+            project.targets[targetName].options &&
+            project.targets[targetName].options.tsConfig) {
+          tsconfigPaths.add(project.targets[targetName].options.tsConfig);
+        }
 
-      if (project.architect &&
-          project.architect[targetName] &&
-          project.architect[targetName].options &&
-          project.architect[targetName].options.tsConfig) {
-        tsconfigPaths.add(project.architect[targetName].options.tsConfig);
-      }
-    });
+        if (project.architect &&
+            project.architect[targetName] &&
+            project.architect[targetName].options &&
+            project.architect[targetName].options.tsConfig) {
+          tsconfigPaths.add(project.architect[targetName].options.tsConfig);
+        }
+      });
+    }
   }
 
   // Filter out tsconfig files that don't exist in the CLI project.
   return Array.from(tsconfigPaths).filter(p => tree.exists(p));
 }
+
+/** Name of the default Angular CLI workspace configuration files. */
+const defaultWorkspaceConfigPaths = ['/angular.json', '/.angular.json'];
+
+/**
+ * Resolve the workspace configuration of the specified tree gracefully. We cannot use the utility
+ * functions from the default Angular schematics because those might not be present in older
+ * versions of the CLI. Also it's important to resolve the workspace gracefully because
+ * the CLI project could be still using `.angular-cli.json` instead of thew new config.
+ */
+function getWorkspaceConfigGracefully(tree: Tree): any {
+  const path = defaultWorkspaceConfigPaths.filter(filePath => tree.exists(filePath))[0];
+  const configBuffer = tree.read(path);
+
+  if (!path || !configBuffer) {
+    return null;
+  }
+
+  try {
+    return JSON.parse(configBuffer.toString());
+  } catch {
+    return null;
+  }
+}