fix: account for non-Angular decorators when inserting decls_before_class (#63)

* fix: account for non-Angular decorators when inserting decls_before_class

When a class has non-Angular decorators (e.g., @log), the const
declarations (_c0, etc.) were inserted between the decorator and
the class statement, producing invalid syntax. Now checks decorator
span positions to insert before any preceding decorators.

Vite/Rolldown's built-in oxc_transformer handles the TS-to-JS
conversion (type stripping, decorator lowering) downstream, so no
additional transform step is needed in the Angular compiler.

Also adds a custom decorator to the playground for testing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: add custom decorator e2e fixtures

Add edge-case fixtures for components with non-Angular class
decorators (single and multiple). Verifies the Angular compiler
preserves custom decorators without breaking generated code.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: Brooooooklyn

crates/oxc_angular_compiler/src/component/transform.rs

@@ -1313,7 +1313,16 @@ pub fn transform_angular_file(
                 if let Some(id) = &class.id {
                     let name = id.name.to_string();
                     if class_definitions.contains_key(&name) {
-                        class_positions.push((name, stmt_start, class.body.span.end));
+                        // Account for non-Angular decorators that precede the class.
+                        // Decorators like @Log(...) appear before `export class` in source,
+                        // so we must insert decls_before_class before those decorators.
+                        let effective_start = class
+                            .decorators
+                            .iter()
+                            .map(|d| d.span.start)
+                            .min()
+                            .map_or(stmt_start, |dec_start| dec_start.min(stmt_start));
+                        class_positions.push((name, effective_start, class.body.span.end));
                     }
                 }
             }

napi/angular-compiler/e2e/compare/fixtures/edge-cases/custom-decorators.fixture.ts

@@ -0,0 +1,61 @@
+/**
+ * Custom (non-Angular) class decorators.
+ *
+ * Tests that non-Angular decorators are preserved in the Angular compiler output
+ * without breaking the generated code. The Angular compiler strips @Component
+ * but must leave custom decorators intact for downstream TS-to-JS tools
+ * (e.g., Rolldown) to lower.
+ */
+import type { Fixture } from '../types.js'
+
+export const fixtures: Fixture[] = [
+  {
+    name: 'single-custom-decorator',
+    category: 'edge-cases',
+    description: 'Component with a single custom class decorator',
+    className: 'MyComponent',
+    type: 'full-transform',
+    sourceCode: `
+import { Component } from '@angular/core';
+
+function Log(message: string) {
+  return function <T extends new (...args: any[]) => any>(target: T): T {
+    console.log(message);
+    return target;
+  };
+}
+
+@Log('MyComponent loaded')
+@Component({
+  selector: 'app-my',
+  template: '<span>hello</span>',
+})
+export class MyComponent {}
+`,
+    expectedFeatures: ['ɵɵdefineComponent', 'ɵfac'],
+  },
+  {
+    name: 'multiple-custom-decorators',
+    category: 'edge-cases',
+    description: 'Component with multiple custom class decorators',
+    className: 'MultiDecoratorComponent',
+    type: 'full-transform',
+    sourceCode: `
+import { Component } from '@angular/core';
+
+function Sealed(target: any) { Object.seal(target); return target; }
+function Track(name: string) {
+  return function(target: any) { return target; };
+}
+
+@Sealed
+@Track('multi')
+@Component({
+  selector: 'app-multi',
+  template: '<div>multi</div>',
+})
+export class MultiDecoratorComponent {}
+`,
+    expectedFeatures: ['ɵɵdefineComponent', 'ɵfac'],
+  },
+]

napi/playground/src/app/app.component.ts

@@ -1,6 +1,9 @@
 import { Component, signal } from '@angular/core'
 import { RouterOutlet } from '@angular/router'
 
+import { Log } from './custom-decorator'
+
+@Log('App component loaded')
 @Component({
   selector: 'app-root',
   imports: [RouterOutlet],

napi/playground/src/app/custom-decorator.ts

@@ -0,0 +1,6 @@
+export function Log(message: string) {
+  return function <T extends new (...args: any[]) => any>(target: T): T {
+    console.log(message)
+    return target
+  }
+}