refactor(compiler-cli): introduce `getExtendedTemplateDiagnosticsForComponent` function (#42984)

Add function to get extended template diagnostics generated by all the template checks.

Refs #42966

PR Close #42984

packages/compiler-cli/src/ngtsc/typecheck/extended/BUILD.bazel

@@ -0,0 +1,15 @@
+load("//tools:defaults.bzl", "ts_library")
+
+ts_library(
+    name = "extended",
+    srcs = glob(
+        ["**/*.ts"],
+    ),
+    visibility = ["//packages/compiler-cli/src/ngtsc:__subpackages__"],
+    deps = [
+        "//packages/compiler-cli/src/ngtsc/diagnostics",
+        "//packages/compiler-cli/src/ngtsc/typecheck/api",
+        "//packages/compiler-cli/src/ngtsc/typecheck/extended/api",
+        "@npm//typescript",
+    ],
+)

packages/compiler-cli/src/ngtsc/typecheck/extended/src/template_checker.ts

@@ -0,0 +1,92 @@
+/**
+ * @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 {ErrorCode} from '../../../diagnostics';
+import {TemplateTypeChecker} from '../../api';
+import {TemplateCheck, TemplateContext} from '../api/api';
+
+/**
+ * Run all `TemplateChecks` for a component and return the generated `ts.Diagnostic`s.
+ * @param component the `@Component()` class from which the template is obtained
+ * @param templateTypeChecker interface to get information about template nodes
+ * @param typeChecker program's type checker
+ * @param templateChecks specific checks to be run
+ * @returns generated `ts.Diagnostic[]`
+ */
+export function getExtendedTemplateDiagnosticsForComponent(
+    component: ts.ClassDeclaration, templateTypeChecker: TemplateTypeChecker,
+    typeChecker: ts.TypeChecker, templateChecks: TemplateCheck<ErrorCode>[]): ts.Diagnostic[] {
+  const template = templateTypeChecker.getTemplate(component);
+  // Skip checks if component has no template. This can happen if the user writes a
+  // `@Component()` but doesn't add the template, could happen in the language service
+  // when users are in the middle of typing code.
+  if (template === null) {
+    return [];
+  }
+  const diagnostics: ts.Diagnostic[] = [];
+
+  const ctx = {templateTypeChecker, typeChecker, component} as TemplateContext;
+
+  for (const check of templateChecks) {
+    diagnostics.push(...deduplicateDiagnostics(check.run(ctx, template)));
+  }
+
+  return diagnostics;
+}
+
+// Filter out duplicated diagnostics, this is possible due to the way the compiler
+// handles desugaring and produces `AST`s. Ex.
+//
+// ```
+// <div *ngIf="true" (foo)="bar">test</div>
+// ```
+//
+// Would result in the following AST:
+//
+// ```
+// Template {
+//   outputs: [
+//    BoundEvent {
+//      name: 'foo',
+//      /.../
+//    }
+//   ],
+//   children: [
+//     Element {
+//       outputs: [
+//         BoundEvent {
+//           name: 'foo',
+//           /.../
+//         }
+//       ]
+//     }
+//   ],
+//   /.../
+// }
+// ```
+//
+// In this case a duplicated diagnostic could be generated for the output `foo`.
+// TODO(danieltrevino): handle duplicated diagnostics when they are being generated
+// to avoid extra work (could be directly in the visitor).
+// https://github.com/angular/angular/pull/42984#discussion_r684823926
+function deduplicateDiagnostics(diagnostics: ts.Diagnostic[]): ts.Diagnostic[] {
+  const result: ts.Diagnostic[] = [];
+  for (const newDiag of diagnostics) {
+    const isDuplicateDiag = result.some(existingDiag => areDiagnosticsEqual(newDiag, existingDiag));
+    if (!isDuplicateDiag) {
+      result.push(newDiag);
+    }
+  }
+  return result;
+}
+
+function areDiagnosticsEqual(first: ts.Diagnostic, second: ts.Diagnostic): boolean {
+  return first.file?.fileName === second.file?.fileName && first.start === second.start &&
+      first.length === second.length && first.code === second.code;
+}