fix(cjs-interop): handle function default exports (#396)

Author: jungwoo3490

src/utils.ts

@@ -124,7 +124,13 @@ function interopDefault(mod: any): any {
         return true;
       }
       if (prop === "default") {
-        return defIsNil ? mod : def;
+        if (defIsNil) {
+          return mod;
+        }
+        if (typeof def?.default === "function" && mod.__esModule) {
+          return def.default; // #396
+        }
+        return def;
       }
       if (Reflect.has(target, prop)) {
         return Reflect.get(target, prop, receiver);

test/__snapshots__/fixtures.test.ts.snap

@@ -4,6 +4,8 @@ exports[`fixtures > async > stdout 1`] = `"works"`;
 
 exports[`fixtures > circular > stdout 1`] = `"a b c"`;
 
+exports[`fixtures > cjs-interop > stdout 1`] = `"CJS function default interop test passed"`;
+
 exports[`fixtures > data-uri > stdout 1`] = `""`;
 
 exports[`fixtures > deps > stdout 1`] = `

test/fixtures/cjs-interop/function-default.cjs

@@ -0,0 +1,6 @@
+module.exports = {
+  __esModule: true,
+  default: function myPlugin() {
+    return "ok";
+  },
+};

test/fixtures/cjs-interop/index.cjs

@@ -0,0 +1,19 @@
+const { createJiti } = require("../../../lib/jiti.cjs");
+const path = require("node:path");
+
+async function main() {
+  const jiti = createJiti(__filename);
+  const modPath = path.resolve(__dirname, "./function-default.cjs");
+
+  const loaded = await jiti.import(modPath, { default: true });
+
+  if (typeof loaded === "function") {
+    console.log("CJS function default interop test passed");
+  } else {
+    console.log("CJS function default interop test failed");
+  }
+}
+
+main().catch((error_) => {
+  console.error("Error:", error_);
+});