fix(core): parse mutator with latest ecmaVersion to support dynamic import

Author: wadakatu

packages/core/src/generators/__tests__/mutator-test-files/dynamic-import-tests/dynamic-import-named-export.ts

@@ -0,0 +1,11 @@
+/* eslint-disable @typescript-eslint/no-unused-vars */
+// Mutator that performs a dynamic import in its body.
+// Regression fixture for https://github.com/orval-labs/orval/issues/1634:
+// esbuild preserves dynamic `import()` in ESM output even when targeting es6,
+// so the bundled code parsed by acorn contains an `import()` expression.
+export const customInstance = async <T>(_config: {
+  url: string;
+}): Promise<T> => {
+  const mod = await import('node:os');
+  return mod as unknown as T;
+};

packages/core/src/generators/mutator-info.test.ts

@@ -259,4 +259,22 @@ describe('getMutatorInfo', () => {
       expect(result).toEqual({ numberOfParams: 0 });
     });
   });
+
+  describe('dynamic import', () => {
+    // Regression test for https://github.com/orval-labs/orval/issues/1634.
+    // esbuild preserves dynamic `import()` in its ESM output, so the bundled
+    // code handed to acorn contains an `import()` expression. Acorn must be
+    // able to parse it; otherwise the named export is reported as missing.
+    it('should find named export when body contains await import()', async () => {
+      const result = await getMutatorInfo(
+        path.join(
+          basePath,
+          'dynamic-import-tests',
+          'dynamic-import-named-export.ts',
+        ),
+        { namedExport: 'customInstance' },
+      );
+      expect(result).toEqual({ numberOfParams: 1 });
+    });
+  });
 });

packages/core/src/generators/mutator-info.ts

@@ -1,12 +1,8 @@
-import { type ecmaVersion, Parser, type Program } from 'acorn';
+import { Parser, type Program } from 'acorn';
 import { build, type BuildOptions } from 'esbuild';
 import { isArray } from 'remeda';
 
-import type {
-  GeneratorMutatorParsingInfo,
-  Tsconfig,
-  TsConfigTarget,
-} from '../types';
+import type { GeneratorMutatorParsingInfo, Tsconfig } from '../types';
 
 export async function getMutatorInfo(
   filePath: string,
@@ -34,11 +30,7 @@ export async function getMutatorInfo(
     tsconfig?.compilerOptions,
   );
 
-  return parseFile(
-    code,
-    namedExport,
-    getEcmaVersion(tsconfig?.compilerOptions?.target),
-  );
+  return parseFile(code, namedExport);
 }
 
 async function bundleFile(
@@ -74,10 +66,17 @@ async function bundleFile(
 function parseFile(
   file: string,
   name: string,
-  ecmaVersion: ecmaVersion = 6,
 ): GeneratorMutatorParsingInfo | undefined {
   try {
-    const ast = Parser.parse(file, { ecmaVersion, sourceType: 'module' });
+    // `file` is esbuild's bundled output, not the user's source. esbuild may
+    // emit any modern syntax (notably dynamic `import()`, which it preserves
+    // even when targeting es6 in ESM mode), so we parse with the latest
+    // ecmaVersion to avoid spurious SyntaxErrors that would mask the export
+    // we are looking for. See https://github.com/orval-labs/orval/issues/1634.
+    const ast = Parser.parse(file, {
+      ecmaVersion: 'latest',
+      sourceType: 'module',
+    });
 
     const foundSpecifier = ast.body
       .filter((x) => x.type === 'ExportNamedDeclaration')
@@ -201,19 +200,3 @@ function parseFunction(
     }
   }
 }
-
-function getEcmaVersion(target?: TsConfigTarget): ecmaVersion | undefined {
-  if (!target) {
-    return;
-  }
-
-  if (target.toLowerCase() === 'esnext') {
-    return 'latest';
-  }
-
-  try {
-    return Number(target.toLowerCase().replace('es', '')) as ecmaVersion;
-  } catch {
-    return;
-  }
-}