refactor(compiler-cli): support running JIT transforms as part of tsickle emit (#56520)

When running the JIT transforms in 1P w/ tsickle, tsickle will
transform source files before our custom transforms can run. This is
also impacting the Ivy transform and hence we use `ts.getOriginalNode`
in various places to inspect the source AST for detecting Angular.

For the JIT transform we need to do a similar change so that the
transform could run in 1P.

PR Close #56520

packages/compiler-cli/src/transformers/jit_transforms/initializer_api_transforms/transform.ts

@@ -70,8 +70,12 @@ function createTransformVisitor(
 ): ts.Visitor<ts.Node, ts.Node> {
   const visitor: ts.Visitor<ts.Node, ts.Node> = (node: ts.Node): ts.Node => {
     if (ts.isClassDeclaration(node) && node.name !== undefined) {
+      const originalNode = ts.getOriginalNode(node, ts.isClassDeclaration);
+      // Note: Attempt to detect the `angularDecorator` on the original node of the class.
+      // That is because e.g. Tsickle or other transforms might have transformed the node
+      // already to transform decorators.
       const angularDecorator = host
-        .getDecoratorsOfDeclaration(node)
+        .getDecoratorsOfDeclaration(originalNode)
         ?.find((d) => decoratorsWithInputs.some((name) => isAngularDecorator(d, name, isCore)));
 
       if (angularDecorator !== undefined) {

packages/compiler-cli/test/initializer_api_transforms_spec.ts

@@ -36,7 +36,11 @@ describe('initializer API metadata transform', () => {
     host = new MockCompilerHost(context);
   });
 
-  function transform(contents: string, postDownlevelDecoratorsTransform = false) {
+  function transform(
+    contents: string,
+    postDownlevelDecoratorsTransform = false,
+    customPreTransform?: ts.TransformerFactory<ts.SourceFile>,
+  ) {
     context.writeFile(TEST_FILE_INPUT, contents);
 
     const program = ts.createProgram(
@@ -59,7 +63,10 @@ describe('initializer API metadata transform', () => {
     const reflectionHost = new TypeScriptReflectionHost(typeChecker);
     const importTracker = new ImportedSymbolsTracker();
     const transformers: ts.CustomTransformers = {
-      before: [getInitializerApiJitTransform(reflectionHost, importTracker, /* isCore */ false)],
+      before: [
+        ...(customPreTransform ? [customPreTransform] : []),
+        getInitializerApiJitTransform(reflectionHost, importTracker, /* isCore */ false),
+      ],
     };
 
     if (postDownlevelDecoratorsTransform) {
@@ -269,6 +276,48 @@ describe('initializer API metadata transform', () => {
       `),
       );
     });
+
+    it('should migrate if the class decorator is downleveled in advance', () => {
+      const fakeDownlevelPreTransform = (ctx: ts.TransformationContext) => {
+        return (sf: ts.SourceFile) => {
+          const visitor = (node: ts.Node) => {
+            if (ts.isClassDeclaration(node)) {
+              return ctx.factory.updateClassDeclaration(
+                node,
+                [],
+                node.name,
+                node.typeParameters,
+                node.heritageClauses,
+                node.members,
+              );
+            }
+            return node;
+          };
+          return ts.visitEachChild(sf, visitor, ctx);
+        };
+      };
+
+      const result = transform(
+        `
+        import {input, Directive} from '@angular/core';
+
+        @Directive({})
+        class MyDir {
+          someInput = input(0);
+        }
+      `,
+        false,
+        fakeDownlevelPreTransform,
+      );
+
+      expect(result).toContain(
+        omitLeadingWhitespace(`
+        __decorate([
+          i0.Input({ isSignal: true, alias: "someInput", required: false, transform: undefined })
+          ], MyDir.prototype, "someInput", void 0);
+      `),
+      );
+    });
   });
 
   describe('model()', () => {