Add browser_only

packages/ppx/browser.ml

@@ -9,7 +9,6 @@ let effect_rule =
         match expression.pexp_desc with
         | Pexp_apply
             ( {
-                (* Ldot (Lident "Prop", str) *)
                 pexp_desc = Pexp_ident { txt = Ldot (Lident _, "useEffect"); _ };
                 pexp_loc_stack;
               },
@@ -23,4 +22,18 @@ let effect_rule =
     (Extension.V3.declare "effect" Extension.Context.expression extractor
        handler)
 
-let () = Driver.V2.register_transformation "browser_ppx" ~rules:[ effect_rule ]
+let browser_only_rule =
+  let extractor = Ast_pattern.(__') in
+  let handler ~ctxt:_ ({ txt = payload; loc } : Ppxlib.Parsetree.payload loc) =
+    match payload with
+    | PStr [ { pstr_desc = Pstr_eval (expression, _); _ } ] ->
+        [%expr fun () -> raise Browser_only]
+    | _ -> [%expr [%ocaml.error "effect only accepts a useEffect expression"]]
+  in
+  Context_free.Rule.extension
+    (Extension.V3.declare "browser_only" Extension.Context.expression extractor
+       handler)
+
+let () =
+  Driver.V2.register_transformation "browser_ppx"
+    ~rules:[ effect_rule; browser_only_rule ]

packages/ppx/dune

@@ -32,6 +32,7 @@
  (public_name server-reason-react.browser_ppx)
  (flags :standard -w -9)
  (libraries ppxlib)
+ (ppx_runtime_libraries runtime)
  (preprocess
   (pps ppxlib.metaquot))
  (kind ppx_rewriter))

packages/ppx/runtime.ml

@@ -0,0 +1 @@
+exception Browser_only

packages/ppx/test_snapshot/input.ml

@@ -112,12 +112,15 @@ let flags_global_multiline_insensitive = [%re "/foo/gim"]
 let scape_digis_with_global = [%re "/(\\d+)/g"]
 let payload_should_be_a_string = [%re apply];;
 
-(* browser *)
+(* effect *)
 
 [%effect
   React.useEffect
     (Js.log "ok";
      (None, [||]))]
-;;
 
-[%effect None]
+let _ = [%effect None]
+
+(* browser_only *)
+let _ = [%browser_only Webapi.Dom.getElementById "foo"]
+let _ = [%browser_only fun () -> ()]

packages/ppx/test_snapshot/output.expected

@@ -90,4 +90,6 @@ let scape_digis_with_global = Js.Re.fromStringWithFlags ~flags:"g" "(\\d+)"
 let payload_should_be_a_string =
   [%ocaml.error "payload should be a string literal"]
 ;;React.useEffect (fun () -> None) [||]
-;;[%ocaml.error "effect only accepts a useEffect expression"]
+let _ = [%ocaml.error "effect only accepts a useEffect expression"]
+let _ = fun () -> raise Browser_only
+let _ = fun () -> raise Browser_only