test(typescript): add test for arbitrary extensions

Author: ychavoya

packages/typescript/test/fixtures/arbitrary-dts/main.ts

@@ -0,0 +1,3 @@
+import module from './module.custom';
+
+export default module.x;

packages/typescript/test/fixtures/arbitrary-dts/module.custom

@@ -0,0 +1,3 @@
+export default {
+    x: 5,
+};

packages/typescript/test/fixtures/arbitrary-dts/module.d.custom.ts

@@ -0,0 +1,4 @@
+declare const CustomModule: {
+    x: Number;
+}
+export default CustomModule;

packages/typescript/test/fixtures/arbitrary-dts/tsconfig.json

@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "allowArbitraryExtensions": true
+    },
+}

packages/typescript/test/test.js

@@ -496,6 +496,18 @@ test.serial('should not resolve .d.ts files', async (t) => {
   t.deepEqual(imports, ['an-import']);
 });
 
+test.serial('should not resolve arbitrary .d.<ext>.ts files', async (t) => {
+  const bundle = await rollup({
+    input: 'fixtures/arbitrary-dts/main.ts',
+    plugins: [typescript({ tsconfig: 'fixtures/arbitrary-dts/tsconfig.json' })],
+    onwarn
+  });
+  const arbitraryDeclarationModules = bundle.cache.modules.filter((module) =>
+    module.id.includes('.d.custom.ts')
+  );
+  t.is(arbitraryDeclarationModules.length, 0);
+});
+
 test.serial('should transpile JSX if enabled', async (t) => {
   process.chdir('fixtures/jsx');