basic completion for exn

Author: zth

analysis/src/CompletionBackEnd.ml

@@ -1277,7 +1277,21 @@ let rec completeTypedValue ~full ~prefix ~completionContext ~mode
           ^ if !Cfg.supportsSnippets then "{$0}" else "{}")
         ~sortText:"A" ~kind:(Value typ) ~env ();
     ]
-  | _ -> []
+  | Tfunction _ -> []
+  | Texn env ->
+    [
+      Completion.create
+        (full.package.builtInCompletionModules.exnModulePath @ ["Error(error)"]
+        |> ident)
+        ~kind:(Label "Catches errors from JavaScript errors.")
+        ~docstring:
+          [
+            "Matches on a JavaScript error. Read more in the [documentation on \
+             catching JS \
+             exceptions](https://rescript-lang.org/docs/manual/latest/exception#catching-js-exceptions).";
+          ]
+        ~env;
+    ]
 
 let rec processCompletable ~debug ~full ~scope ~env ~pos ~forHover
     (completable : Completable.t) =

analysis/src/Packages.ml

@@ -111,6 +111,7 @@ let newBsPackage ~rootPath =
                     promiseModulePath = ["Promise"];
                     listModulePath = ["List"];
                     resultModulePath = ["Result"];
+                    exnModulePath = ["Exn"];
                   }
                  else if
                  opens_from_bsc_flags
@@ -129,6 +130,7 @@ let newBsPackage ~rootPath =
                      promiseModulePath = ["Js"; "Promise"];
                      listModulePath = ["List"];
                      resultModulePath = ["Result"];
+                     exnModulePath = ["Js"; "Exn"];
                    }
                  else
                    {
@@ -140,6 +142,7 @@ let newBsPackage ~rootPath =
                      promiseModulePath = ["Js"; "Promise"];
                      listModulePath = ["Belt"; "List"];
                      resultModulePath = ["Belt"; "Result"];
+                     exnModulePath = ["Js"; "Exn"];
                    });
              })))
     | None -> None)

analysis/src/SharedTypes.ml

@@ -298,6 +298,7 @@ type polyVariantConstructor = {name: string; args: Types.type_expr list}
 type completionType =
   | Tuple of QueryEnv.t * Types.type_expr list * Types.type_expr
   | Toption of QueryEnv.t * completionType
+  | Texn of QueryEnv.t
   | Tbool of QueryEnv.t
   | Tarray of QueryEnv.t * completionType
   | Tstring of QueryEnv.t
@@ -519,6 +520,7 @@ type builtInCompletionModules = {
   promiseModulePath: string list;
   listModulePath: string list;
   resultModulePath: string list;
+  exnModulePath: string list;
 }
 
 type package = {

analysis/src/TypeUtils.ml

@@ -119,6 +119,7 @@ let rec extractType ~env ~package (t : Types.type_expr) =
     |> Option.map (fun payloadTyp -> Tarray (env, payloadTyp))
   | Tconstr (Path.Pident {name = "bool"}, [], _) -> Some (Tbool env)
   | Tconstr (Path.Pident {name = "string"}, [], _) -> Some (Tstring env)
+  | Tconstr (Path.Pident {name = "exn"}, [], _) -> Some (Texn env)
   | Tconstr (path, _, _) -> (
     match References.digConstructor ~env ~package path with
     | Some (env, {item = {decl = {type_manifest = Some t1}}}) ->
@@ -421,6 +422,7 @@ let rec extractedTypeToString ?(inner = false) = function
   | Trecord {definition = `NameOnly name; fields} ->
     if inner then name else printRecordFromFields ~name fields
   | TinlineRecord {fields} -> printRecordFromFields fields
+  | Texn _ -> "exn"
 
 let unwrapCompletionTypeIfOption (t : SharedTypes.completionType) =
   match t with

analysis/tests/src/CompletionPattern.res

@@ -201,3 +201,8 @@ let ff: recordWithFn = {someFn: () => ()}
 
 // switch ff { | {someFn: }}
 //                       ^com
+
+let xn: exn = Obj.magic()
+
+// switch xn { | }
+//              ^com

analysis/tests/src/expected/CompletionPattern.res.txt

@@ -905,8 +905,19 @@ Completable: Cpattern Value[s]->tuple($1)
   }]
 
 Complete src/CompletionPattern.res 201:25
-posCursor:[201:25] posNoWhite:[201:24] Found expr:[201:3->201:28]
+posCursor:[201:25] posNoWhite:[201:24] Found expr:[201:3->204:25]
 posCursor:[201:25] posNoWhite:[201:24] Found pattern:[201:17->201:28]
 Completable: Cpattern Value[ff]->recordField(someFn)
 []
 
+Complete src/CompletionPattern.res 206:16
+XXX Not found!
+Completable: Cpattern Value[xn]
+[{
+    "label": "Js.Exn.Error(error)",
+    "kind": 4,
+    "tags": [],
+    "detail": "Catches errors from JavaScript errors.",
+    "documentation": {"kind": "markdown", "value": "Matches on a JavaScript error. Read more in the [documentation on catching JS exceptions](https://rescript-lang.org/docs/manual/latest/exception#catching-js-exceptions)."}
+  }]
+