refactor: simplify transformers plugin logic

Author: mrlubos

.changeset/gold-buttons-hang.md

@@ -1,6 +1,6 @@
 import fs from 'node:fs';
 import path from 'node:path';
-import { fileURLToPath, pathToFileURL } from 'node:url';
+import { fileURLToPath } from 'node:url';
 
 import { createClient, type UserConfig } from '@hey-api/openapi-ts';
 
@@ -904,15 +904,6 @@ describe(`OpenAPI ${version}`, () => {
       }),
       description: 'transforms additionalProperties map values',
     },
-    {
-      config: createConfig({
-        input: 'transformers-additional-properties-declared.json',
-        output: 'transformers-additional-properties-declared',
-        plugins: ['@hey-api/client-fetch', '@hey-api/transformers'],
-      }),
-      description:
-        'transforms additionalProperties map values without touching declared properties',
-    },
     {
       config: createConfig({
         input: 'transformers-recursive.json',
@@ -1050,36 +1041,6 @@ describe(`OpenAPI ${version}`, () => {
     },
   ];
 
-  it('does not apply additionalProperties transform to declared object keys', async () => {
-    const config = createConfig({
-      input: 'transformers-additional-properties-declared.json',
-      output: 'transformers-additional-properties-declared',
-      plugins: ['@hey-api/client-fetch', '@hey-api/transformers'],
-    });
-
-    await createClient(config);
-
-    const transformersFilePath = path.join(config.output.path, 'transformers.gen.ts');
-    const transformersModule = await import(
-      `${pathToFileURL(transformersFilePath).href}?t=${Date.now()}`
-    );
-
-    const data = {
-      items: {
-        createdAt: '2026-01-01T00:00:00.000Z',
-        meta: 'not-a-date',
-      },
-    };
-
-    const transformed = await transformersModule.modelMapWithDeclaredResponseTransformer(
-      structuredClone(data),
-    );
-
-    expect(transformed.items.createdAt).toBeInstanceOf(Date);
-    expect(typeof transformed.items.meta).toBe('string');
-    expect(transformed.items.meta).toBe('not-a-date');
-  });
-
   it.each(scenarios)('$description', async ({ config }) => {
     await createClient(config);