refactor: improve tsconfig parsing for update-tool

Improves the tsconfig parsing for the update-tool so that errors
are actually reported. We do not want to silently proceed migrating
a project if the tsconfig does not exist, could not be parsed etc.
Currently this works by accident as we just let TypeScript include/glob
for all TS files in the project directory.

Author: devversion

src/cdk/schematics/ng-update/devkit-migration-rule.ts

@@ -98,7 +98,8 @@ export function createMigrationSchematicRule(
       // In some applications, developers will have global stylesheets which are not
       // specified in any Angular component. Therefore we glob up all CSS and SCSS files
       // in the project and migrate them if needed.
-      // TODO: rework this to collect global stylesheets from the workspace config. COMP-280.
+      // TODO: rework this to collect global stylesheets from the workspace config.
+      // TODO: https://github.com/angular/components/issues/24032.
       const additionalStylesheetPaths = findStylesheetFiles(tree, project.root);
 
       if (buildTsconfigPath !== null) {

src/cdk/schematics/ng-update/public-api.ts

@@ -9,6 +9,7 @@
 export * from './data/index';
 export * from './devkit-migration';
 export * from './devkit-migration-rule';
+export * from './devkit-file-system';
 export * from './html-parsing/angular';
 export * from './html-parsing/elements';
 export * from './typescript/base-types';

src/cdk/schematics/testing/test-case-setup.ts

@@ -73,7 +73,7 @@ export async function createTestCaseSetup(
   runner.logger.subscribe(entry => (logOutput += `${entry.message}\n`));
   const {appTree, writeFile} = await createFileSystemTestApp(runner);
 
-  _patchTypeScriptDefaultLib(appTree);
+  patchDevkitTreeToExposeTypeScript(appTree);
 
   // Write each test-case input to the file-system. This is necessary because otherwise
   // TypeScript compiler API won't be able to pick up the test cases.
@@ -219,7 +219,7 @@ export function defineJasmineTestCases(
  * default library typings. These need to be readable in unit tests because otherwise
  * type checking within migration rules is not working as in real applications.
  */
-export function _patchTypeScriptDefaultLib(tree: Tree) {
+export function patchDevkitTreeToExposeTypeScript<T extends Tree>(tree: T): T {
   const _originalRead = tree.read;
   tree.read = function (filePath: Path) {
     // In case a file within the TypeScript package is requested, we read the file from
@@ -232,4 +232,5 @@ export function _patchTypeScriptDefaultLib(tree: Tree) {
       return _originalRead.call(this, filePath);
     }
   };
+  return tree;
 }

src/cdk/schematics/update-tool/index.ts

@@ -183,6 +183,8 @@ export class UpdateProject<Context> {
   /**
    * Creates a program form the specified tsconfig and patches the host
    * to read files and directories through the given file system.
+   *
+   * @throws {TsconfigParseError} If the tsconfig could not be parsed.
    */
   static createProgramFromTsconfig(tsconfigPath: WorkspacePath, fs: FileSystem): ts.Program {
     const parsed = parseTsconfigFile(fs.resolve(tsconfigPath), fs);

src/cdk/schematics/update-tool/utils/diagnostics.ts

@@ -0,0 +1,17 @@
+/**
+ * @license
+ * Copyright Google LLC 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 * as ts from 'typescript';
+import {FileSystem} from '../file-system';
+import {createFormatDiagnosticHost} from './virtual-host';
+
+/** Formats the specified diagnostics with respect to the given file system. */
+export function formatDiagnostics(diagnostics: ts.Diagnostic[], fileSystem: FileSystem): string {
+  const formatHost = createFormatDiagnosticHost(fileSystem);
+  return ts.formatDiagnosticsWithColorAndContext(diagnostics, formatHost);
+}

src/cdk/schematics/update-tool/utils/parse-tsconfig.ts

@@ -10,16 +10,44 @@ import * as ts from 'typescript';
 import {FileSystem, WorkspacePath} from '../file-system';
 import {FileSystemHost} from './virtual-host';
 import {dirname} from 'path';
+import {formatDiagnostics} from './diagnostics';
 
+/** Class capturing a tsconfig parse error. */
+export class TsconfigParseError extends Error {}
+
+/**
+ * Attempts to parse the specified tsconfig file.
+ *
+ * @throws {TsconfigParseError} If the tsconfig could not be read or parsed.
+ */
 export function parseTsconfigFile(
   tsconfigPath: WorkspacePath,
   fileSystem: FileSystem,
 ): ts.ParsedCommandLine {
-  const {config} = ts.readConfigFile(tsconfigPath, p => fileSystem.read(fileSystem.resolve(p))!);
-  return ts.parseJsonConfigFileContent(
+  if (!fileSystem.fileExists(tsconfigPath)) {
+    throw new TsconfigParseError(`Tsconfig cannot not be read: ${tsconfigPath}`);
+  }
+
+  const {config, error} = ts.readConfigFile(
+    tsconfigPath,
+    p => fileSystem.read(fileSystem.resolve(p))!,
+  );
+
+  // If there is a config reading error, we never attempt to parse the config.
+  if (error) {
+    throw new TsconfigParseError(formatDiagnostics([error], fileSystem));
+  }
+
+  const parsed = ts.parseJsonConfigFileContent(
     config,
     new FileSystemHost(fileSystem),
     dirname(tsconfigPath),
     {},
   );
+
+  if (parsed.errors.length) {
+    throw new TsconfigParseError(formatDiagnostics(parsed.errors, fileSystem));
+  }
+
+  return parsed;
 }

src/cdk/schematics/update-tool/utils/virtual-host.ts

@@ -114,3 +114,12 @@ export function createFileSystemCompilerHost(
 
   return host;
 }
+
+/** Creates a format diagnostic host that works with the given file system. */
+export function createFormatDiagnosticHost(fileSystem: FileSystem): ts.FormatDiagnosticsHost {
+  return {
+    getCanonicalFileName: p => fileSystem.resolve(p),
+    getCurrentDirectory: () => '/',
+    getNewLine: () => '\n',
+  };
+}