refactor(language-service): add generic decorator property verifications (#32252)

This PR makes finding class declarations properties in decorators are
applied to more generic to all properties that may be in a decorator,
and adds helper methods enabling getting the property assignment of a
property value and verifying that a property assignment is actually in a
decorator applied to a class.

This is done so that it will be easier to provide Angular definitions
for decorator properties moving forward. Most immediately, this will
provide decorator class verification for #32238.

PR Close #32252

packages/language-service/src/template.ts

@@ -127,30 +127,34 @@ export class ExternalTemplate extends BaseTemplate {
 }
 
 /**
- * Given a template node, return the ClassDeclaration node that corresponds to
- * the component class for the template.
+ * Returns a property assignment from the assignment value, or `undefined` if there is no
+ * assignment.
+ */
+export function getPropertyAssignmentFromValue(value: ts.Node): ts.PropertyAssignment|undefined {
+  if (!value.parent || !ts.isPropertyAssignment(value.parent)) {
+    return;
+  }
+  return value.parent;
+}
+
+/**
+ * Given a decorator property assignment, return the ClassDeclaration node that corresponds to the
+ * directive class the property applies to.
+ * If the property assignment is not on a class decorator, no declaration is returned.
  *
  * For example,
  *
  * @Component({
- *   template: '<div></div>' <-- template node
+ *   template: '<div></div>'
+ *   ^^^^^^^^^^^^^^^^^^^^^^^---- property assignment
  * })
  * class AppComponent {}
  *           ^---- class declaration node
  *
- * @param node template node
+ * @param propAsgn property assignment
  */
-export function getClassDeclFromTemplateNode(node: ts.Node): ts.ClassDeclaration|undefined {
-  if (!ts.isStringLiteralLike(node)) {
-    return;
-  }
-  if (!node.parent || !ts.isPropertyAssignment(node.parent)) {
-    return;
-  }
-  const propAsgnNode = node.parent;
-  if (propAsgnNode.name.getText() !== 'template') {
-    return;
-  }
+export function getClassDeclFromDecoratorProp(propAsgnNode: ts.PropertyAssignment):
+    ts.ClassDeclaration|undefined {
   if (!propAsgnNode.parent || !ts.isObjectLiteralExpression(propAsgnNode.parent)) {
     return;
   }
@@ -169,3 +173,14 @@ export function getClassDeclFromTemplateNode(node: ts.Node): ts.ClassDeclaration
   const classDeclNode = decorator.parent;
   return classDeclNode;
 }
+
+/**
+ * Determines if a property assignment is on a class decorator.
+ * See `getClassDeclFromDecoratorProperty`, which gets the class the decorator is applied to, for
+ * more details.
+ *
+ * @param prop property assignment
+ */
+export function isClassDecoratorProperty(propAsgn: ts.PropertyAssignment): boolean {
+  return !!getClassDeclFromDecoratorProp(propAsgn);
+}

packages/language-service/src/typescript_host.ts

@@ -13,7 +13,7 @@ import * as ts from 'typescript';
 import {AstResult, isAstResult} from './common';
 import {createLanguageService} from './language_service';
 import {ReflectorHost} from './reflector_host';
-import {ExternalTemplate, InlineTemplate, getClassDeclFromTemplateNode} from './template';
+import {ExternalTemplate, InlineTemplate, getClassDeclFromDecoratorProp, getPropertyAssignmentFromValue} from './template';
 import {Declaration, DeclarationError, Diagnostic, DiagnosticKind, DiagnosticMessageChain, LanguageService, LanguageServiceHost, Span, TemplateSource} from './types';
 import {findTightestNode, getDirectiveClassLike} from './utils';
 
@@ -310,7 +310,11 @@ export class TypeScriptServiceHost implements LanguageServiceHost {
     if (!ts.isStringLiteralLike(node)) {
       return;
     }
-    const classDecl = getClassDeclFromTemplateNode(node);
+    const tmplAsgn = getPropertyAssignmentFromValue(node);
+    if (!tmplAsgn || tmplAsgn.name.getText() !== 'template') {
+      return;
+    }
+    const classDecl = getClassDeclFromDecoratorProp(tmplAsgn);
     if (!classDecl || !classDecl.name) {  // Does not handle anonymous class
       return;
     }