fix(js): enhance TypeScript transformer loading to support function-based plugins (#31443)

## Current Behavior

TypeScript transformer loading in the js package was limited to standard
Nx/TypeScript transformer plugins and didnt handle different exports

## Expected Behavior

TypeScript transformer loading should support various function-based
transformer formats in a generic way

## Related Issue(s)

Fixes #31411

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
Co-authored-by: Coly010 <Coly010@users.noreply.github.com>

packages/js/src/utils/typescript/__mocks__/function-after-declarations-plugin.ts

@@ -0,0 +1,3 @@
+export const afterDeclarations = (options: any, program: any) => {
+  return () => {}; // Mock transformer factory
+};

packages/js/src/utils/typescript/__mocks__/function-after-plugin.ts

@@ -0,0 +1,3 @@
+export const after = (options: any, program: any) => {
+  return () => {}; // Mock transformer factory
+};

packages/js/src/utils/typescript/__mocks__/function-direct-export.ts

@@ -0,0 +1,3 @@
+export default (options, program) => {
+  return () => {};
+};

packages/js/src/utils/typescript/__mocks__/function-multiple-hooks.ts

@@ -0,0 +1,11 @@
+export const before = (options: any, program: any) => {
+  return () => {}; // Mock transformer factory
+};
+
+export const after = (options: any, program: any) => {
+  return () => {}; // Mock transformer factory
+};
+
+export const afterDeclarations = (options: any, program: any) => {
+  return () => {}; // Mock transformer factory
+};

packages/js/src/utils/typescript/__mocks__/plugin-a.ts

@@ -1 +1,3 @@
-export const before = () => {};
+export const before = (options: any, program: any) => {
+  return () => {}; // Mock transformer factory
+};

packages/js/src/utils/typescript/__mocks__/plugin-b.ts

@@ -1 +1,3 @@
-export const after = () => {};
+export const after = (options: any, program: any) => {
+  return () => {}; // Mock transformer factory
+};

packages/js/src/utils/typescript/load-ts-transformers.spec.ts

@@ -2,6 +2,10 @@ import { loadTsTransformers } from './load-ts-transformers';
 
 jest.mock('plugin-a');
 jest.mock('plugin-b');
+jest.mock('function-after-plugin');
+jest.mock('function-after-declarations-plugin');
+jest.mock('function-direct-export');
+jest.mock('function-multiple-hooks');
 const mockRequireResolve = jest.fn((path) => path);
 
 describe('loadTsTransformers', () => {
@@ -29,6 +33,62 @@ describe('loadTsTransformers', () => {
     });
   });
 
+  it('should handle function-based after transformers', () => {
+    const result = loadTsTransformers(
+      ['function-after-plugin'],
+      mockRequireResolve as any
+    );
+
+    expect(result.hasPlugin).toEqual(true);
+    expect(result.compilerPluginHooks).toEqual({
+      beforeHooks: [],
+      afterHooks: [expect.any(Function)],
+      afterDeclarationsHooks: [],
+    });
+  });
+
+  it('should handle function-based afterDeclarations transformers', () => {
+    const result = loadTsTransformers(
+      ['function-after-declarations-plugin'],
+      mockRequireResolve as any
+    );
+
+    expect(result.hasPlugin).toEqual(true);
+    expect(result.compilerPluginHooks).toEqual({
+      beforeHooks: [],
+      afterHooks: [],
+      afterDeclarationsHooks: [expect.any(Function)],
+    });
+  });
+
+  it('should handle direct function export transformers', () => {
+    const result = loadTsTransformers(
+      ['function-direct-export'],
+      mockRequireResolve as any
+    );
+
+    expect(result.hasPlugin).toEqual(true);
+    expect(result.compilerPluginHooks).toEqual({
+      beforeHooks: [expect.any(Function)],
+      afterHooks: [],
+      afterDeclarationsHooks: [],
+    });
+  });
+
+  it('should handle function-based transformers with multiple hooks', () => {
+    const result = loadTsTransformers(
+      ['function-multiple-hooks'],
+      mockRequireResolve as any
+    );
+
+    expect(result.hasPlugin).toEqual(true);
+    expect(result.compilerPluginHooks).toEqual({
+      beforeHooks: [expect.any(Function)],
+      afterHooks: [expect.any(Function)],
+      afterDeclarationsHooks: [expect.any(Function)],
+    });
+  });
+
   function assertEmptyResult(result: ReturnType<typeof loadTsTransformers>) {
     expect(result.hasPlugin).toEqual(false);
     expect(result.compilerPluginHooks).toEqual({

packages/js/src/utils/typescript/load-ts-transformers.ts

@@ -7,6 +7,76 @@ import {
   TransformerPlugin,
 } from './types';
 
+enum TransformerFormat {
+  STANDARD, // Standard TypeScript transformer API: { before, after, afterDeclarations }
+  FUNCTION_EXPORT, // Function-based: exports a function or { before: Function }
+  UNKNOWN, // Unknown format
+}
+
+function detectTransformerFormat(plugin: any): TransformerFormat {
+  // Check if it's a standard Nx/TypeScript transformer plugin
+  if (plugin && (plugin.before || plugin.after || plugin.afterDeclarations)) {
+    return TransformerFormat.STANDARD;
+  }
+
+  // Check if it's a function-based transformer (exports a function directly)
+  if (typeof plugin === 'function') {
+    return TransformerFormat.FUNCTION_EXPORT;
+  }
+
+  // Check if it has a function export (function-based plugin pattern)
+  if (
+    plugin &&
+    (typeof plugin.before === 'function' ||
+      typeof plugin.after === 'function' ||
+      typeof plugin.afterDeclarations === 'function')
+  ) {
+    return TransformerFormat.FUNCTION_EXPORT;
+  }
+
+  return TransformerFormat.UNKNOWN;
+}
+
+function adaptFunctionBasedTransformer(
+  plugin: any,
+  pluginOptions: Record<string, unknown>
+) {
+  // Handle direct function export
+  if (typeof plugin === 'function') {
+    return {
+      before: (options: Record<string, unknown>, program: any) =>
+        plugin(options, program),
+    };
+  }
+
+  // Handle object with function exports - adapt all available hooks
+  if (plugin && typeof plugin === 'object') {
+    const adapted: any = {};
+
+    if (typeof plugin.before === 'function') {
+      adapted.before = (options: Record<string, unknown>, program: any) =>
+        plugin.before(options, program);
+    }
+
+    if (typeof plugin.after === 'function') {
+      adapted.after = (options: Record<string, unknown>, program: any) =>
+        plugin.after(options, program);
+    }
+
+    if (typeof plugin.afterDeclarations === 'function') {
+      adapted.afterDeclarations = (
+        options: Record<string, unknown>,
+        program: any
+      ) => plugin.afterDeclarations(options, program);
+    }
+
+    // Return adapted hooks if any were found, otherwise return original plugin
+    return Object.keys(adapted).length > 0 ? adapted : plugin;
+  }
+
+  return plugin;
+}
+
 export function loadTsTransformers(
   plugins: TransformerEntry[],
   moduleResolver: typeof require.resolve = require.resolve
@@ -43,7 +113,18 @@ export function loadTsTransformers(
       const binaryPath = moduleResolver(name, {
         paths: nodeModulePaths,
       });
-      return require(binaryPath);
+      const loadedPlugin = require(binaryPath);
+      // Check if main export already has transformer hooks
+      if (
+        loadedPlugin &&
+        (loadedPlugin.before ||
+          loadedPlugin.after ||
+          loadedPlugin.afterDeclarations)
+      ) {
+        return loadedPlugin;
+      }
+      // Only fall back to .default if main export lacks transformer hooks
+      return loadedPlugin?.default ?? loadedPlugin;
     } catch (e) {
       logger.warn(`"${name}" plugin could not be found!`);
       return {};
@@ -52,26 +133,71 @@ export function loadTsTransformers(
 
   for (let i = 0; i < pluginRefs.length; i++) {
     const { name: pluginName, options: pluginOptions } = normalizedPlugins[i];
-    const { before, after, afterDeclarations } = pluginRefs[i];
-    if (!before && !after && !afterDeclarations) {
+    let plugin = pluginRefs[i];
+
+    // Skip empty plugins (failed to load)
+    if (
+      !plugin ||
+      (typeof plugin !== 'function' && Object.keys(plugin).length === 0)
+    ) {
+      continue;
+    }
+
+    const format = detectTransformerFormat(plugin);
+
+    // Adapt function-based transformers to standard format
+    if (format === TransformerFormat.FUNCTION_EXPORT) {
+      logger.debug(`Adapting function-based transformer: ${pluginName}`);
+      plugin = adaptFunctionBasedTransformer(plugin, pluginOptions);
+    } else if (format === TransformerFormat.UNKNOWN) {
       logger.warn(
-        `${pluginName} is not a Transformer Plugin. It does not provide neither before(), after(), nor afterDeclarations()`
+        `${pluginName} is not a recognized Transformer Plugin format. It should export ` +
+          `{ before?, after?, afterDeclarations? } functions or be a function-based transformer.`
       );
       continue;
     }
 
+    const { before, after, afterDeclarations } = plugin;
+
+    // Validate that at least one hook is available
+    if (!before && !after && !afterDeclarations) {
+      logger.warn(
+        `${pluginName} does not provide any transformer hooks (before, after, or afterDeclarations).`
+      );
+      continue;
+    }
+
+    // Add hooks with proper error handling
     if (before) {
-      beforeHooks.push(before.bind(before, pluginOptions));
+      try {
+        beforeHooks.push((program) => before(pluginOptions, program));
+      } catch (error) {
+        logger.error(
+          `Failed to register 'before' transformer for ${pluginName}: ${error.message}`
+        );
+      }
     }
 
     if (after) {
-      afterHooks.push(after.bind(after, pluginOptions));
+      try {
+        afterHooks.push((program) => after(pluginOptions, program));
+      } catch (error) {
+        logger.error(
+          `Failed to register 'after' transformer for ${pluginName}: ${error.message}`
+        );
+      }
     }
 
     if (afterDeclarations) {
-      afterDeclarationsHooks.push(
-        afterDeclarations.bind(afterDeclarations, pluginOptions)
-      );
+      try {
+        afterDeclarationsHooks.push((program) =>
+          afterDeclarations(pluginOptions, program)
+        );
+      } catch (error) {
+        logger.error(
+          `Failed to register 'afterDeclarations' transformer for ${pluginName}: ${error.message}`
+        );
+      }
     }
   }
 

packages/js/src/utils/typescript/types.ts

@@ -31,6 +31,35 @@ export interface CompilerPlugin {
   ) => TransformerFactory;
 }
 
+/**
+ * Extended plugin interface to support different transformer API formats
+ * including function-based transformers and direct function exports
+ */
+export type AnyCompilerPlugin =
+  | CompilerPlugin
+  | ((
+      options?: Record<string, unknown>,
+      program?: Program
+    ) => TransformerFactory)
+  | {
+      before: (
+        options?: Record<string, unknown>,
+        program?: Program
+      ) => TransformerFactory;
+    }
+  | {
+      after: (
+        options?: Record<string, unknown>,
+        program?: Program
+      ) => TransformerFactory;
+    }
+  | {
+      afterDeclarations: (
+        options?: Record<string, unknown>,
+        program?: Program
+      ) => TransformerFactory;
+    };
+
 export interface CompilerPluginHooks {
   beforeHooks: Array<(program?: Program) => TransformerFactory>;
   afterHooks: Array<(program?: Program) => TransformerFactory>;