Hoist exports to allow circular dependencies (#9024)

packages/core/integration-tests/test/integration/js-export-default-fn-circular-anonymous/a.mjs

@@ -0,0 +1 @@
+import "./b.mjs";

packages/core/integration-tests/test/integration/js-export-default-fn-circular-anonymous/b.mjs

@@ -0,0 +1,7 @@
+import { c } from "./c.mjs"; // imports and calls b1 (circular)
+
+export default function () {
+	return "b1";
+}
+
+let str = c + "str";

packages/core/integration-tests/test/integration/js-export-default-fn-circular-anonymous/c.mjs

@@ -0,0 +1,5 @@
+import b1 from "./b.mjs";
+
+export const c = b1();
+
+result(c);

packages/core/integration-tests/test/integration/js-export-default-fn-circular-named/a.mjs

@@ -0,0 +1 @@
+import "./b.mjs";

packages/core/integration-tests/test/integration/js-export-default-fn-circular-named/b.mjs

@@ -0,0 +1,7 @@
+import { c } from "./c.mjs"; // imports and calls b1 (circular)
+
+export default function b1() {
+	return "b1";
+}
+
+let str = c + "str";

packages/core/integration-tests/test/integration/js-export-default-fn-circular-named/c.mjs

@@ -0,0 +1,5 @@
+import b1 from "./b.mjs";
+
+export const c = b1();
+
+result(c);

packages/core/integration-tests/test/javascript.js

@@ -5235,6 +5235,38 @@ describe('javascript', function () {
     assert.deepEqual(res, {other: 1});
   });
 
+  it('should hoist function default exports to allow circular imports', async function () {
+    let b = await bundle(
+      path.join(
+        __dirname,
+        '/integration/js-export-default-fn-circular-named/a.mjs',
+      ),
+    );
+
+    let output;
+    function result(v) {
+      output = v;
+    }
+    await run(b, {result});
+    assert.deepEqual(output, 'b1');
+  });
+
+  it('should hoist anonymous function default exports to allow circular imports', async function () {
+    let b = await bundle(
+      path.join(
+        __dirname,
+        '/integration/js-export-default-fn-circular-anonymous/a.mjs',
+      ),
+    );
+
+    let output;
+    function result(v) {
+      output = v;
+    }
+    await run(b, {result});
+    assert.deepEqual(output, 'b1');
+  });
+
   it('should work with many different types of exports', async function () {
     let b = await bundle(
       path.join(__dirname, 'integration/js-export-many/index.js'),

packages/transformers/js/core/src/modules.rs

@@ -460,20 +460,16 @@ impl Fold for ESMFold {
                       declare: false,
                       function: func.function.clone(),
                     }))));
-                    items.push(self.create_exports_assign(
-                      "default".into(),
-                      Expr::Ident(ident.clone()),
-                      DUMMY_SP,
-                    ));
+                    self.create_export("default".into(), Expr::Ident(ident.clone()), DUMMY_SP);
                   } else {
-                    items.push(self.create_exports_assign(
+                    self.create_export(
                       "default".into(),
                       Expr::Fn(FnExpr {
                         ident: None,
                         function: func.function.clone(),
                       }),
                       export.span,
-                    ));
+                    );
                   }
                 }
                 _ => {