From 13d880d239d9b938c8788ddf675a92778e913549 Mon Sep 17 00:00:00 2001
From: Cristiano Calcagno <cristianoc@users.noreply.github.com>
Date: Thu, 3 Jul 2025 14:32:00 +0200
Subject: [PATCH] Fix issue with preserve mode where `jsx` is declared as an
 external without a `@module` attribute

Fixes https://github.com/rescript-lang/rescript/pull/7577
---
 CHANGELOG.md                          |  1 +
 compiler/core/js_dump.ml              | 11 ++++++-----
 tests/tests/src/jsx_preserve_test.mjs |  8 ++++++++
 tests/tests/src/jsx_preserve_test.res | 13 +++++++++++++
 4 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 80d734f216..7d70ae26fe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,6 +40,7 @@
 - Prop punning when types don't match results in I/O error: _none_: No such file or directory. https://github.com/rescript-lang/rescript/pull/7533
 - Pass location to children prop in jsx ppx. https://github.com/rescript-lang/rescript/pull/7540
 - Fix crash when `bs-g` is used with untagged variants. https://github.com/rescript-lang/rescript/pull/7575
+- Fix issue with preserve mode where `jsx` is declared as an external without a `@module` attribute. https://github.com/rescript-lang/rescript/pull/7591
 
 #### :nail_care: Polish
 
diff --git a/compiler/core/js_dump.ml b/compiler/core/js_dump.ml
index 99bfce9140..1684aa056c 100644
--- a/compiler/core/js_dump.ml
+++ b/compiler/core/js_dump.ml
@@ -533,12 +533,13 @@ and expression_desc cxt ~(level : int) f x : cxt =
       ( ({
            expression_desc =
              J.Var
-               (J.Qualified
-                  ( _,
-                    Some fnName
-                    (* We care about the function name when it is jsxs,
+               ( Id {name = fnName}
+               | J.Qualified
+                   ( _,
+                     Some fnName
+                     (* We care about the function name when it is jsxs,
                        If this is the case, we need to unpack an array later on *)
-                  ));
+                   ) );
          } as e),
         el,
         {call_transformed_jsx = true} )
diff --git a/tests/tests/src/jsx_preserve_test.mjs b/tests/tests/src/jsx_preserve_test.mjs
index 3c71b71dc7..9cf576055e 100644
--- a/tests/tests/src/jsx_preserve_test.mjs
+++ b/tests/tests/src/jsx_preserve_test.mjs
@@ -208,6 +208,12 @@ let _props_with_hyphen = <label
   data-testid={"test"}
 />;
 
+let React = {};
+
+let _fragment = <Fragment>
+  {"Hello, world!"}
+</Fragment>;
+
 export {
   Icon,
   _single_element_child,
@@ -234,5 +240,7 @@ export {
   ComponentWithOptionalProps,
   _optional_props,
   _props_with_hyphen,
+  React,
+  _fragment,
 }
 /* _single_element_child Not a pure module */
diff --git a/tests/tests/src/jsx_preserve_test.res b/tests/tests/src/jsx_preserve_test.res
index 1c83f06f26..f9e0cf1661 100644
--- a/tests/tests/src/jsx_preserve_test.res
+++ b/tests/tests/src/jsx_preserve_test.res
@@ -128,3 +128,16 @@ module ComponentWithOptionalProps = {
 let _optional_props = <ComponentWithOptionalProps i=1 s="test" element={<div />} />
 
 let _props_with_hyphen = <label ariaLabel={"close sidebar"} dataTestId="test" />
+
+module React = {
+  type component<'props> = Jsx.component<'props>
+  type element = Jsx.element
+
+  external jsx: (component<'props>, 'props) => element = "jsx"
+
+  type fragmentProps = {children?: element}
+
+  external jsxFragment: component<fragmentProps> = "Fragment"
+}
+
+let _fragment = <> {Jsx.string("Hello, world!")} </>