feat(core): add undecorated classes migration schematic (#31650)

Introduces a new migration schematic that follows the given
migration plan: https://hackmd.io/@alx/S1XKqMZeS.

First case: The schematic detects decorated directives which
inherit a constructor. The migration ensures that all base
classes until the class with the explicit constructor are
properly decorated with "@Directive()" or "@Component". In
case one of these classes is not decorated, the schematic
adds the abstract "@Directive()" decorator automatically.

Second case: The schematic detects undecorated declarations
and copies the inherited "@Directive()", "@Component" or
"@Pipe" decorator to the undecorated derived class. This
involves non-trivial import rewriting, identifier aliasing
and AOT metadata serializing
(as decorators are not always part of source files)

PR Close #31650

packages/core/schematics/utils/ng_decorators.ts

@@ -15,6 +15,7 @@ export type CallExpressionDecorator = ts.Decorator & {
 
 export interface NgDecorator {
   name: string;
+  moduleName: string;
   node: CallExpressionDecorator;
   importNode: ts.ImportDeclaration;
 }
@@ -30,6 +31,7 @@ export function getAngularDecorators(
       .map(({node, importData}) => ({
              node: node as CallExpressionDecorator,
              name: importData !.name,
+             moduleName: importData !.importModule,
              importNode: importData !.node
            }));
 }

packages/core/schematics/utils/typescript/class_declaration.ts

@@ -30,3 +30,8 @@ export function findParentClassDeclaration(node: ts.Node): ts.ClassDeclaration|n
   }
   return node;
 }
+
+/** Checks whether the given class declaration has an explicit constructor or not. */
+export function hasExplicitConstructor(node: ts.ClassDeclaration): boolean {
+  return node.members.some(ts.isConstructorDeclaration);
+}

packages/core/schematics/utils/typescript/symbol.ts

@@ -0,0 +1,20 @@
+/**
+ * @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 * as ts from 'typescript';
+
+export function getValueSymbolOfDeclaration(node: ts.Node, typeChecker: ts.TypeChecker): ts.Symbol|
+    undefined {
+  let symbol = typeChecker.getSymbolAtLocation(node);
+
+  while (symbol && symbol.flags & ts.SymbolFlags.Alias) {
+    symbol = typeChecker.getAliasedSymbol(symbol);
+  }
+
+  return symbol;
+}