From 51caa4bbd03e2d67866271c13d3a8b1b00db11ce Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Tue, 9 Dec 2025 09:45:02 +0100
Subject: [PATCH 1/4] Fix invalid JSX being generated for empty fragments

---
 compiler/core/js_dump.ml              | 13 ++++++++++++-
 tests/tests/src/jsx_preserve_test.mjs |  3 +++
 tests/tests/src/jsx_preserve_test.res |  2 ++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/compiler/core/js_dump.ml b/compiler/core/js_dump.ml
index ea1c3d5fda..9eedb10d87 100644
--- a/compiler/core/js_dump.ml
+++ b/compiler/core/js_dump.ml
@@ -1116,6 +1116,12 @@ and print_jsx cxt ?(spread_props : J.expression option)
     (* A user defined component or external component *)
     | _ -> expression ~level cxt f tag
   in
+  let is_fragment =
+    match tag.expression_desc with
+    | J.Var (J.Qualified ({id = {name = "JsxRuntime"}}, Some "Fragment")) ->
+      true
+    | _ -> false
+  in
   let children_opt =
     List.find_map
       (fun (n, e) ->
@@ -1129,6 +1135,11 @@ and print_jsx cxt ?(spread_props : J.expression option)
           else Some [e]
         else None)
       fields
+    (* For fragments without children we normalize to an empty list so they
+       print as <></> instead of </> which is invalid JSX. *)
+    |> function
+    | None when is_fragment -> Some []
+    | other -> other
   in
   let print_props cxt props =
     (* If a key is present, should be printed before the spread props,
@@ -1169,7 +1180,7 @@ and print_jsx cxt ?(spread_props : J.expression option)
       match children_opt with
       | Some _ -> cxt
       | None ->
-        (* Put a space the tag name and /> *)
+        (* Put a space between the tag name and /> *)
         P.space f;
         cxt)
     else
diff --git a/tests/tests/src/jsx_preserve_test.mjs b/tests/tests/src/jsx_preserve_test.mjs
index 3622e7901d..570ca4607c 100644
--- a/tests/tests/src/jsx_preserve_test.mjs
+++ b/tests/tests/src/jsx_preserve_test.mjs
@@ -192,6 +192,8 @@ let _props_with_hyphen = <label
   data-testid={"test"}
 />;
 
+let _empty_fragment = <></>;
+
 let _fragment = <>
   {"Hello, world!"}
 </>;
@@ -271,6 +273,7 @@ export {
   ComponentWithOptionalProps,
   _optional_props,
   _props_with_hyphen,
+  _empty_fragment,
   _fragment,
   _youtube_iframe,
   X,
diff --git a/tests/tests/src/jsx_preserve_test.res b/tests/tests/src/jsx_preserve_test.res
index e5900a7fdd..aeeaad1531 100644
--- a/tests/tests/src/jsx_preserve_test.res
+++ b/tests/tests/src/jsx_preserve_test.res
@@ -124,6 +124,8 @@ let _optional_props = <ComponentWithOptionalProps i=1 s="test" element={<div />}
 
 let _props_with_hyphen = <label ariaLabel={"close sidebar"} dataTestId="test" />
 
+let _empty_fragment = <> </>
+
 let _fragment = <> {Jsx.string("Hello, world!")} </>
 
 let _youtube_iframe =

From e6b1d46376092a2f5a4014006ba2c4523980a949 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Tue, 9 Dec 2025 14:07:30 +0100
Subject: [PATCH 2/4] Reduce code duplication

---
 compiler/core/js_dump.ml | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/compiler/core/js_dump.ml b/compiler/core/js_dump.ml
index 9eedb10d87..5c68466fc8 100644
--- a/compiler/core/js_dump.ml
+++ b/compiler/core/js_dump.ml
@@ -1105,6 +1105,12 @@ and print_indented_list (f : P.t) (parent_expr_level : int) (cxt : cxt)
 and print_jsx cxt ?(spread_props : J.expression option)
     ?(key : J.expression option) ~(level : int) f (fnName : string)
     (tag : J.expression) (fields : (string * J.expression) list) : cxt =
+  let is_fragment =
+    match tag.expression_desc with
+    | J.Var (J.Qualified ({id = {name = "JsxRuntime"}}, Some "Fragment")) ->
+      true
+    | _ -> false
+  in
   let print_tag cxt =
     match tag.expression_desc with
     (* "div" or any other primitive tag *)
@@ -1112,16 +1118,10 @@ and print_jsx cxt ?(spread_props : J.expression option)
       P.string f txt;
       cxt
     (* fragment *)
-    | J.Var (J.Qualified ({id = {name = "JsxRuntime"}}, Some "Fragment")) -> cxt
+    | _ when is_fragment -> cxt
     (* A user defined component or external component *)
     | _ -> expression ~level cxt f tag
   in
-  let is_fragment =
-    match tag.expression_desc with
-    | J.Var (J.Qualified ({id = {name = "JsxRuntime"}}, Some "Fragment")) ->
-      true
-    | _ -> false
-  in
   let children_opt =
     List.find_map
       (fun (n, e) ->

From ec8a5eecab4872d84b8f697e4408036c67b81d60 Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Tue, 9 Dec 2025 14:08:43 +0100
Subject: [PATCH 3/4] Added TODO

---
 compiler/core/js_dump.ml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/compiler/core/js_dump.ml b/compiler/core/js_dump.ml
index 5c68466fc8..43967a3f1c 100644
--- a/compiler/core/js_dump.ml
+++ b/compiler/core/js_dump.ml
@@ -1105,6 +1105,8 @@ and print_indented_list (f : P.t) (parent_expr_level : int) (cxt : cxt)
 and print_jsx cxt ?(spread_props : J.expression option)
     ?(key : J.expression option) ~(level : int) f (fnName : string)
     (tag : J.expression) (fields : (string * J.expression) list) : cxt =
+  (* TODO: make fragment detection respect custom JSX runtime modules instead of
+     assuming "JsxRuntime". *)
   let is_fragment =
     match tag.expression_desc with
     | J.Var (J.Qualified ({id = {name = "JsxRuntime"}}, Some "Fragment")) ->

From 5a55f160e955337b039e6f80e711dbbc7fc9807a Mon Sep 17 00:00:00 2001
From: Christoph Knittel <ck@cca.io>
Date: Tue, 9 Dec 2025 14:29:19 +0100
Subject: [PATCH 4/4] CHANGELOG

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 744da2a53e..861c9cb811 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,7 @@
 - Fix signature matching for externals when abstract alias hides function arity. https://github.com/rescript-lang/rescript/pull/8045
 - Fix arity detection for arrows returning nested generics. https://github.com/rescript-lang/rescript/pull/8064
 - Fix error handling when rescript.json parsing fails and improve error message. https://github.com/rescript-lang/rescript/pull/8067
+- Fix invalid JSX being generated for empty fragments. https://github.com/rescript-lang/rescript/pull/8077
 
 #### :memo: Documentation