Fix browser_only inside fn

packages/ppx/browser.ml

@@ -26,6 +26,28 @@ let effect_rule =
     (Extension.V3.declare "effect" Extension.Context.expression extractor
        handler)
 
+let browser_only_value_binding pattern expression =
+  let loc = pattern.ppat_loc in
+  match pattern with
+  | [%pat? ()] -> Builder.value_binding ~loc ~pat:pattern ~expr:[%expr ()]
+  | _ -> (
+      match expression.pexp_desc with
+      | Pexp_fun (_arg_label, _arg_expression, fun_pattern, _expression) ->
+          let stringified = Ppxlib.Pprintast.string_of_expression expression in
+          let message = Builder.estring ~loc stringified in
+          Builder.value_binding ~loc ~pat:pattern
+            ~expr:
+              [%expr
+                fun [%p fun_pattern] ->
+                  (raise
+                     (ReactDOM.Impossible_in_ssr [%e message]) [@warning "-27"])]
+      | _ ->
+          Builder.value_binding ~loc ~pat:pattern
+            ~expr:
+              [%expr
+                [%ocaml.error
+                  "browser only works on expressions or function definitions"]])
+
 let browser_only_on_expressions_rule =
   let extractor = Ast_pattern.(single_expr_payload __) in
   let handler ~ctxt payload =
@@ -41,12 +63,19 @@ let browser_only_on_expressions_rule =
             let message = Builder.estring ~loc stringified in
             [%expr
               raise ReactDOM.Impossible_in_ssr [%e message] [@warning "-27"]]
-        | Pexp_fun (_arg_label, _arg_expression, _pattern, _expression) ->
+        | Pexp_fun (_arg_label, _arg_expression, fun_pattern, _expression) ->
             let stringified = Ppxlib.Pprintast.string_of_expression payload in
             let message = Builder.estring ~loc stringified in
             [%expr
-              fun () ->
+              fun [%p fun_pattern] ->
                 (raise ReactDOM.Impossible_in_ssr [%e message] [@warning "-27"])]
+        | Pexp_let (rec_flag, value_bindings, expression) ->
+            Builder.pexp_let ~loc rec_flag
+              (List.map
+                 (fun binding ->
+                   browser_only_value_binding binding.pvb_pat binding.pvb_expr)
+                 value_bindings)
+              expression
         | _ ->
             [%expr
               [%ocaml.error

packages/ppx/test_snapshot/dune

@@ -1,12 +1,12 @@
 (executable
- (name main)
+ (name test_standalone)
  (libraries pipe_first_ppx double_hash_ppx regex_ppx browser_ppx ppxlib))
 
 (rule
  (targets ocaml.preprocessed)
  (deps ocaml.ml)
  (action
-  (run ./main.exe --impl %{deps} -o %{targets})))
+  (run ./test_standalone.exe --impl %{deps} -o %{targets})))
 
 (rule
  (targets reason.preprocessed)
@@ -17,7 +17,7 @@
    (with-stdout-to
     %{targets}
     (run refmt --parse re --print ml %{input}))
-   (run ./main.exe --impl %{targets} -o %{targets})
+   (run ./test_standalone.exe --impl %{targets} -o %{targets})
    (run refmt --parse ml --print re --in-place %{targets}))))
 
 (rule

packages/ppx/test_snapshot/ocaml.expected

@@ -93,9 +93,6 @@ let payload_should_be_a_string =
 let _ = [%ocaml.error "effect only accepts a useEffect expression"]
 let _ = ((raise ReactDOM.Impossible_in_ssr "Webapi.Dom.getElementById")
   [@warning "-27"])
-let _ =
-  fun () -> ((raise ReactDOM.Impossible_in_ssr "fun () -> ()")
-    [@warning "-27"])
 let valueFromEvent = Webapi.Dom.getElementById "foo"
 let valueFromEvent evt =
   raise

packages/ppx/test_snapshot/ocaml.ml

@@ -123,7 +123,6 @@ let _ = [%effect None]
 
 (* browser_only *)
 let _ = [%browser_only Webapi.Dom.getElementById "foo"]
-let _ = [%browser_only fun () -> ()]
 
 let%browser_only valueFromEvent = Webapi.Dom.getElementById "foo"
 let%browser_only valueFromEvent evt = Webapi.Dom.getElementById "foo"

packages/ppx/test_snapshot/reason.expected

@@ -1,7 +1,17 @@
-[@warning "-27"]
-let loadInitialText = () =>
-  raise(
-    ReactDOM.Impossible_in_ssr(
-      "fun () ->\n  setHtmlFetchState Loading;\n  (((((WcApi.fetchHTML WcConstants.initialText) |. Promise.flatMap)\n       (fun html ->\n          (onChange (html |. WcStringHelpers.htmlToText)) |. Promise.resolved))\n      |. Promise.Js.catch)\n     (fun _ -> (setHtmlFetchState Error) |. Promise.resolved))\n    |. ignore",
-    ),
-  );
+let make = () => {
+  let loadInitialText = () =>
+    [@warning "-27"]
+    raise(
+      ReactDOM.Impossible_in_ssr(
+        "fun () ->\n  setHtmlFetchState Loading;\n  (((((WcApi.fetchHTML WcConstants.initialText) |. Promise.flatMap)\n       (fun html ->\n          (onChange (html |. WcStringHelpers.htmlToText)) |. Promise.resolved))\n      |. Promise.Js.catch)\n     (fun _ -> (setHtmlFetchState Error) |. Promise.resolved))\n    |. ignore",
+      ),
+    );
+  let loadInitialText = argument1 =>
+    [@warning "-27"]
+    raise(
+      ReactDOM.Impossible_in_ssr(
+        "fun argument1 ->\n  fun argument2 ->\n    setHtmlFetchState Loading;\n    (((((WcApi.fetchHTML WcConstants.initialText) |. Promise.flatMap)\n         (fun html ->\n            (onChange (html |. WcStringHelpers.htmlToText)) |.\n              Promise.resolved))\n        |. Promise.Js.catch)\n       (fun _ -> (setHtmlFetchState Error) |. Promise.resolved))\n      |. ignore",
+      ),
+    );
+  React.createElement("div");
+};

packages/ppx/test_snapshot/reason.re

@@ -1,7 +1,23 @@
-let%browser_only loadInitialText = () => {
-  setHtmlFetchState(Loading);
-  WcApi.fetchHTML(WcConstants.initialText)
-  ->Promise.flatMap(html => onChange(html->WcStringHelpers.htmlToText)->Promise.resolved)
-  ->Promise.Js.catch(_ => setHtmlFetchState(Error)->Promise.resolved)
-  ->ignore;
+let make = () => {
+  let%browser_only loadInitialText = () => {
+    setHtmlFetchState(Loading);
+    WcApi.fetchHTML(WcConstants.initialText)
+    ->Promise.flatMap(html =>
+        onChange(html->WcStringHelpers.htmlToText)->Promise.resolved
+      )
+    ->Promise.Js.catch(_ => setHtmlFetchState(Error)->Promise.resolved)
+    ->ignore;
+  };
+
+  let%browser_only loadInitialText = (argument1, argument2) => {
+    setHtmlFetchState(Loading);
+    WcApi.fetchHTML(WcConstants.initialText)
+    ->Promise.flatMap(html =>
+        onChange(html->WcStringHelpers.htmlToText)->Promise.resolved
+      )
+    ->Promise.Js.catch(_ => setHtmlFetchState(Error)->Promise.resolved)
+    ->ignore;
+  };
+
+  React.createElement("div");
 };