deprecate and migrate Exn.Error to JsExn

Author: tsnobip

CHANGELOG.md

@@ -10,6 +10,12 @@
 > - :nail_care: [Polish]
 > - :house: [Internal]
 
+# 12.0.1 (unreleased)
+
+#### :nail_care: Polish
+
+- Add missing deprecation and migration for Exn.Error. https://github.com/rescript-lang/rescript/pull/8036
+
 # 12.0.0
 
 No changes compared to rc.5.

packages/@rescript/runtime/Stdlib_Exn.resi

@@ -33,7 +33,13 @@ Provide utilities for dealing with JS exceptions.
 })
 type t
 
-type exn += private Error(t)
+type exn +=
+  private
+  | @deprecated({
+    reason: "Use `JsExn` instead",
+    migrate: %replace.variant(JsExn),
+  })
+  Error(t)
 
 @deprecated({
   reason: "Use `JsExn.fromException` instead",

tests/tools_tests/src/expected/StdlibMigration_Exn.res.expected

@@ -39,3 +39,13 @@ let throws5 = () => JsError.SyntaxError.throwWithMessage("err")
 let throws6 = () => JsError.TypeError.throwWithMessage("err")
 let throws7 = () => JsError.URIError.throwWithMessage("err")
 
+let someThrowingJsCode = () => Some("bar")
+let catchingExnErrorWithSwitch = switch someThrowingJsCode() {
+| exception JsExn(e) => e->JsExn.message
+| s => s
+}
+
+let catchingExnErrorWithTryCatch = try {someThrowingJsCode()} catch {
+| JsExn(e) => e->JsExn.message
+}
+

tests/tools_tests/src/migrate/StdlibMigration_Exn.res

@@ -38,3 +38,13 @@ let throws4 = () => Exn.raiseReferenceError("err")
 let throws5 = () => Exn.raiseSyntaxError("err")
 let throws6 = () => Exn.raiseTypeError("err")
 let throws7 = () => Exn.raiseUriError("err")
+
+let someThrowingJsCode = () => Some("bar")
+let catchingExnErrorWithSwitch = switch someThrowingJsCode() {
+| exception Exn.Error(e) => e->Exn.message
+| s => s
+}
+
+let catchingExnErrorWithTryCatch = try {someThrowingJsCode()} catch {
+| Exn.Error(e) => e->Exn.message
+}

tests/tools_tests/src/migrate/migrated/Migrated_StdlibMigration_Exn.res

@@ -40,3 +40,13 @@ let throws4 = () => JsError.ReferenceError.throwWithMessage("err")
 let throws5 = () => JsError.SyntaxError.throwWithMessage("err")
 let throws6 = () => JsError.TypeError.throwWithMessage("err")
 let throws7 = () => JsError.URIError.throwWithMessage("err")
+
+let someThrowingJsCode = () => Some("bar")
+let catchingExnErrorWithSwitch = switch someThrowingJsCode() {
+| exception JsExn(e) => e->JsExn.message
+| s => s
+}
+
+let catchingExnErrorWithTryCatch = try {someThrowingJsCode()} catch {
+| JsExn(e) => e->JsExn.message
+}

tools/src/migrate.ml

@@ -104,6 +104,10 @@ module MapperUtils = struct
       if Ext_list.is_empty attrs then e
       else {e with pexp_attributes = attrs @ e.pexp_attributes}
 
+    let attach_attrs_to_pat ~attrs (pat : Parsetree.pattern) =
+      if Ext_list.is_empty attrs then pat
+      else {pat with ppat_attributes = attrs @ pat.ppat_attributes}
+
     (* Apply transforms attached to an expression itself and drop the
        transform attributes afterwards. *)
     let apply_on_self (e : Parsetree.expression) : Parsetree.expression =
@@ -332,6 +336,29 @@ module TypeReplace = struct
     | _ -> None
 end
 
+module VariantReplace = struct
+  type target = {lid: Longident.t Location.loc; attrs: Parsetree.attributes}
+
+  let of_template (expr : Parsetree.expression) : target option =
+    match expr.pexp_desc with
+    | Pexp_extension
+        ( {txt = "replace.variant"},
+          PStr
+            [
+              {
+                pstr_desc =
+                  Pstr_eval
+                    ({pexp_desc = Pexp_construct (lid, _); pexp_attributes}, _);
+              };
+            ] ) ->
+      let attrs =
+        if Ext_list.is_empty expr.pexp_attributes then pexp_attributes
+        else expr.pexp_attributes @ pexp_attributes
+      in
+      Some {lid; attrs}
+    | _ -> None
+end
+
 let remap_needed_extensions (mapper : Ast_mapper.mapper)
     (ext : Parsetree.extension) : Parsetree.extension =
   match ext with
@@ -551,6 +578,29 @@ let makeMapper (deprecated_used : Cmt_utils.deprecated_used list) =
   |> List.iter (fun ({Cmt_utils.source_loc} as d) ->
          Hashtbl.replace loc_to_deprecated_reference source_loc d);
 
+  let deprecated_variant_constructors =
+    deprecated_used
+    |> List.filter_map (fun (d : Cmt_utils.deprecated_used) ->
+           match d.migration_template with
+           | Some template -> (
+             match VariantReplace.of_template template with
+             | Some target -> Some (d.source_loc, target)
+             | None -> None)
+           | None -> None)
+  in
+  let loc_to_deprecated_variant_constructor =
+    Hashtbl.create (List.length deprecated_variant_constructors)
+  in
+  deprecated_variant_constructors
+  |> List.iter (fun (loc, target) ->
+         Hashtbl.replace loc_to_deprecated_variant_constructor loc target);
+
+  let find_variant_target ~loc ~lid_loc =
+    match Hashtbl.find_opt loc_to_deprecated_variant_constructor loc with
+    | Some _ as found -> found
+    | None -> Hashtbl.find_opt loc_to_deprecated_variant_constructor lid_loc
+  in
+
   (* Helpers for type replacement lookups *)
   let loc_contains (a : Location.t) (b : Location.t) =
     let a_start = a.Location.loc_start.pos_cnum in
@@ -629,6 +679,13 @@ let makeMapper (deprecated_used : Cmt_utils.deprecated_used list) =
             match deprecated_info.migration_template with
             | Some e -> apply_template_direct mapper e call_args exp
             | None -> exp)
+          | {pexp_desc = Pexp_construct (lid, arg); pexp_loc} -> (
+            match find_variant_target ~loc:pexp_loc ~lid_loc:lid.loc with
+            | Some {VariantReplace.lid; attrs} ->
+              let arg = Option.map (mapper.expr mapper) arg in
+              let replaced = {exp with pexp_desc = Pexp_construct (lid, arg)} in
+              MapperUtils.ApplyTransforms.attach_to_replacement ~attrs replaced
+            | None -> Ast_mapper.default_mapper.expr mapper exp)
           | {
            pexp_desc =
              Pexp_apply
@@ -664,6 +721,17 @@ let makeMapper (deprecated_used : Cmt_utils.deprecated_used list) =
                 ~pipe_args ~funct exp
             | Some _ -> Ast_mapper.default_mapper.expr mapper exp)
           | _ -> Ast_mapper.default_mapper.expr mapper exp);
+      pat =
+        (fun mapper pat ->
+          match pat with
+          | {ppat_desc = Ppat_construct (lid, arg); ppat_loc} -> (
+            match find_variant_target ~loc:ppat_loc ~lid_loc:lid.loc with
+            | Some {VariantReplace.lid; attrs} ->
+              let arg = Option.map (mapper.pat mapper) arg in
+              let replaced = {pat with ppat_desc = Ppat_construct (lid, arg)} in
+              MapperUtils.ApplyTransforms.attach_attrs_to_pat ~attrs replaced
+            | None -> Ast_mapper.default_mapper.pat mapper pat)
+          | _ -> Ast_mapper.default_mapper.pat mapper pat);
     }
   in
   mapper