fix(language-service): Clear caches when program changes (#21337)

This commit fixes a bug whereby the caches are not cleared when the
program changes. This subsequently produces the incorrect error of
'Component ... is not included in a module ...'.

PR Close #19405

PR Close #21337

packages/language-service/test/diagnostics_spec.ts

@@ -248,7 +248,7 @@ describe('diagnostics', () => {
           template: \`
             <div *ngIf="comps | async; let comps; else loading">
             </div>
-            <ng-template #loading>Loading comps...</ng-template>            
+            <ng-template #loading>Loading comps...</ng-template>
           \`
         })
         export class MyComponent {}

packages/language-service/test/typescript_host_spec.ts

@@ -46,4 +46,20 @@ describe('completions', () => {
     ngHost = new TypeScriptServiceHost(host, service);
     expect(() => ngHost.getAnalyzedModules()).not.toThrow();
   });
+
+  it('should clear the caches if program changes', () => {
+    // First create a TypescriptHost with empty script names
+    host = new MockTypescriptHost([], toh);
+    service = ts.createLanguageService(host);
+    ngHost = new TypeScriptServiceHost(host, service);
+    expect(ngHost.getAnalyzedModules().ngModules).toEqual([]);
+    // Now add a script, this would change the program
+    const fileName = '/app/main.ts';
+    const content = (host as MockTypescriptHost).getFileContent(fileName) !;
+    (host as MockTypescriptHost).addScript(fileName, content);
+    // If the caches are not cleared, we would get back an empty array.
+    // But if the caches are cleared then the analyzed modules will be non-empty.
+    expect(ngHost.getAnalyzedModules().ngModules.length).not.toEqual(0);
+  });
+
 });