fix(language-service): ignore hover of symbols not in the TypeScript program (#17969)

Fixes: #17965

packages/compiler-cli/src/diagnostics/symbols.ts

@@ -322,7 +322,7 @@ export interface SymbolQuery {
   /**
    * Return the type symbol for the given static symbol.
    */
-  getTypeSymbol(type: StaticSymbol): Symbol;
+  getTypeSymbol(type: StaticSymbol): Symbol|undefined;
 
   /**
    * Return the members that are in the context of a type's template reference.

packages/compiler-cli/src/diagnostics/typescript_symbols.ts

@@ -159,10 +159,10 @@ class TypeScriptSymbolQuery implements SymbolQuery {
     }
   }
 
-  getTypeSymbol(type: StaticSymbol): Symbol {
+  getTypeSymbol(type: StaticSymbol): Symbol|undefined {
     const context: TypeContext = {node: this.source, program: this.program, checker: this.checker};
-    const typeSymbol = findClassSymbolInContext(type, context) !;
-    return new SymbolWrapper(typeSymbol, context);
+    const typeSymbol = findClassSymbolInContext(type, context);
+    return typeSymbol && new SymbolWrapper(typeSymbol, context);
   }
 
   createSymbolTable(symbols: SymbolDeclaration[]): SymbolTable {

packages/compiler-cli/test/diagnostics/symbol_query_spec.ts

@@ -0,0 +1,108 @@
+/**
+ * @license
+ * Copyright Google Inc. 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 {StaticSymbol} from '@angular/compiler';
+import {AngularCompilerOptions, CompilerHost} from '@angular/compiler-cli';
+import {EmittingCompilerHost, MockAotCompilerHost, MockCompilerHost, MockData, MockDirectory, MockMetadataBundlerHost, arrayToMockDir, arrayToMockMap, isSource, settings, setup, toMockFileArray} from '@angular/compiler/test/aot/test_util';
+import * as ts from 'typescript';
+
+import {Symbol, SymbolQuery, SymbolTable} from '../../src/diagnostics/symbols';
+import {getSymbolQuery} from '../../src/diagnostics/typescript_symbols';
+import {Directory} from '../mocks';
+
+import {DiagnosticContext, MockLanguageServiceHost} from './mocks';
+
+function emptyPipes(): SymbolTable {
+  return {
+    size: 0,
+    get(key: string) { return undefined; },
+    has(key: string) { return false; },
+    values(): Symbol[]{return [];}
+  };
+}
+
+describe('symbol query', () => {
+  let program: ts.Program;
+  let checker: ts.TypeChecker;
+  let sourceFile: ts.SourceFile;
+  let query: SymbolQuery;
+  let context: DiagnosticContext;
+  beforeEach(() => {
+    const registry = ts.createDocumentRegistry(false, '/src');
+    const host = new MockLanguageServiceHost(
+        ['/quickstart/app/app.component.ts'], QUICKSTART, '/quickstart');
+    const service = ts.createLanguageService(host, registry);
+    program = service.getProgram();
+    checker = program.getTypeChecker();
+    sourceFile = program.getSourceFile('/quickstart/app/app.component.ts');
+    const options: AngularCompilerOptions = Object.create(host.getCompilationSettings());
+    options.genDir = '/dist';
+    options.basePath = '/quickstart';
+    const aotHost = new CompilerHost(program, options, host, {verboseInvalidExpression: true});
+    context = new DiagnosticContext(service, program, checker, aotHost);
+    query = getSymbolQuery(program, checker, sourceFile, emptyPipes)
+  });
+
+  it('should be able to get undefined for an unknown symbol', () => {
+    const unknownType = context.getStaticSymbol('/unkonwn/file.ts', 'UnknownType');
+    const symbol = query.getTypeSymbol(unknownType);
+    expect(symbol).toBeUndefined();
+  });
+});
+
+function appComponentSource(template: string): string {
+  return `
+    import {Component} from '@angular/core';
+
+    export interface Person {
+      name: string;
+      address: Address;
+    }
+
+    export interface Address {
+      street: string;
+      city: string;
+      state: string;
+      zip: string;
+    }
+
+    @Component({
+      template: '${template}'
+    })
+    export class AppComponent {
+      name = 'Angular';
+      person: Person;
+      people: Person[];
+      maybePerson?: Person;
+
+      getName(): string { return this.name; }
+      getPerson(): Person { return this.person; }
+      getMaybePerson(): Person | undefined { this.maybePerson; }
+    }
+  `;
+}
+
+const QUICKSTART: Directory = {
+  quickstart: {
+    app: {
+      'app.component.ts': appComponentSource('<h1>Hello {{name}}</h1>'),
+      'app.module.ts': `
+        import { NgModule }      from '@angular/core';
+        import { toString }      from './utils';
+
+        import { AppComponent }  from './app.component';
+
+        @NgModule({
+          declarations: [ AppComponent ],
+          bootstrap:    [ AppComponent ]
+        })
+        export class AppModule { }
+      `
+    }
+  }
+};