Fix issue with preserve mode where jsx is declared as an external without a @module attribute

Fixes #7577

Author: cristianoc

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
 

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} )

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 */

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!")} </>