fix(language-service): Paths on Windows should be normalized (#40492)

Many `ts.LanguageService` APIs accept a filename, for example
```ts
getQuickInfoAtPosition(fileName: string, position: number)
```
The requirement is that `fileName` is agnostic to the platform (Linux, Mac,
Windows, etc), and is always normalized to TypeScript's internal
`NormalizedPath`.

This is evident from the way these APIs are called from the language server:
```ts
  private onHover(params: lsp.TextDocumentPositionParams) {
    const lsInfo = this.getLSAndScriptInfo(params.textDocument);
    if (lsInfo === undefined) {
      return;
    }
    const {languageService, scriptInfo} = lsInfo;
    const offset = lspPositionToTsPosition(scriptInfo, params.position);
    const info = languageService.getQuickInfoAtPosition(scriptInfo.fileName, offset);
    // ...
  }
```
9fca9c6651/server/src/session.ts (L594)
Here `scriptInfo.fileName` is always a `ts.server.NormalizedPath`.

However, https://github.com/angular/angular/pull/39917 accidentally leaked
the platform-specific paths, and caused a mismatch between the incoming paths
and the paths stored in the internal data structure `fileToComponent`.

This PR fixes the bug by always normalizing the paths, and updating the
type to reflect the format of the underlying data.

Fixes https://github.com/angular/vscode-ng-language-service/issues/1063

PR Close #40492

packages/language-service/src/typescript_host.ts

@@ -62,7 +62,12 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
   private readonly staticSymbolResolver: StaticSymbolResolver;
 
   private readonly staticSymbolCache = new StaticSymbolCache();
-  private readonly fileToComponent = new Map<string, StaticSymbol>();
+  /**
+   * Key of the `fileToComponent` map must be TS internal normalized path (path
+   * separator must be `/`), value of the map is the StaticSymbol for the
+   * Component class declaration.
+   */
+  private readonly fileToComponent = new Map<ts.server.NormalizedPath, StaticSymbol>();
   private readonly collectedErrors = new Map<string, any[]>();
   private readonly fileVersions = new Map<string, string>();
   private readonly urlResolver: UrlResolver;
@@ -165,7 +170,7 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
   /**
    * Return all known external templates.
    */
-  getExternalTemplates(): string[] {
+  getExternalTemplates(): ts.server.NormalizedPath[] {
     return [...this.fileToComponent.keys()];
   }
 
@@ -210,7 +215,7 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
           const templateName = this.urlResolver.resolve(
               this.reflector.componentModuleUrl(directive.reference),
               metadata.template.templateUrl);
-          this.fileToComponent.set(templateName, directive.reference);
+          this.fileToComponent.set(tss.server.toNormalizedPath(templateName), directive.reference);
         }
       }
     }
@@ -417,7 +422,7 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
     }
     const source = snapshot.getText(0, snapshot.getLength());
     // Next find the component class symbol
-    const classSymbol = this.fileToComponent.get(fileName);
+    const classSymbol = this.fileToComponent.get(tss.server.toNormalizedPath(fileName));
     if (!classSymbol) {
       return;
     }

packages/language-service/test/typescript_host_spec.ts

@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import * as path from 'path';
 import * as ts from 'typescript';
 
 import {TypeScriptServiceHost} from '../src/typescript_host';
@@ -114,7 +115,7 @@ describe('TypeScriptServiceHost', () => {
     const tsLS = ts.createLanguageService(tsLSHost);
     const ngLSHost = new TypeScriptServiceHost(tsLSHost, tsLS);
     ngLSHost.getAnalyzedModules();
-    expect(ngLSHost.getExternalTemplates()).toContain('/app/#inner/inner.html');
+    expect(ngLSHost.getExternalTemplates() as string[]).toContain('/app/#inner/inner.html');
   });
 
   // https://github.com/angular/angular/issues/32301
@@ -265,4 +266,19 @@ describe('TypeScriptServiceHost', () => {
     newModules = ngLSHost.getAnalyzedModules();
     expect(newModules.ngModules.length).toBeGreaterThan(0);
   });
+
+  it('should normalize path on Windows', () => {
+    // Spy on the `path.resolve()` method called by the URL resolver and mimic
+    // behavior on Windows.
+    spyOn(path, 'resolve').and.callFake((...pathSegments: string[]) => {
+      return path.win32.resolve(...pathSegments);
+    });
+    const tsLSHost = new MockTypescriptHost(['/app/main.ts']);
+    const tsLS = ts.createLanguageService(tsLSHost);
+    const ngLSHost = new TypeScriptServiceHost(tsLSHost, tsLS);
+    ngLSHost.getAnalyzedModules();
+    const externalTemplates: string[] = ngLSHost.getExternalTemplates();
+    // External templates should be normalized.
+    expect(externalTemplates).toContain('/app/test.ng');
+  });
 });