Feature: Support Inlay Hint

CHANGELOG.md

@@ -12,6 +12,9 @@
 
 ## master
 
+#### :rocket: New Feature
+
+- Inlay Hints (experimetal). `rescript.settings.inlayHints.enable: true`
 ## v1.4.2
 
 #### :bug: Bug Fix

README.md

@@ -105,6 +105,18 @@ The extension will look for the existence of a `/node_modules/.bin/rescript` fil
 
 To override this lookup process, the path can be configured explicitly using the setting `rescript.settings.binaryPath`.
 
+### Inlay Hints (experimental)
+
+This allows an editor to place annotations inline with text to display type hints.
+
+```jsonc
+// Enable (experimental) inlay hints.
+rescript.settings.inlayHints.enable: true
+
+// Maximum length of character for inlay hints. Set to null to have an unlimited length. Inlay hints that exceed the maximum length will not be shown
+rescript.settings.inlayHints.maxLength: 25
+```
+
 ### Hide generated files
 
 You can configure VSCode to collapse the JavaScript files ReScript generates under its source ReScript file. This will "hide" the generated files in the VSCode file explorer, but still leaving them accessible by expanding the source ReScript file they belong to.

analysis/examples/larger-project/.merlin

@@ -1,12 +1,12 @@
 ####{BSB GENERATED: NO EDIT
-FLG -ppx '/Users/cristianocalcagno/GitHub/rescript-vscode/analysis/examples/larger-project/node_modules/rescript/darwin/bsc.exe -as-ppx -bs-jsx 3'
-S /Users/cristianocalcagno/GitHub/rescript-vscode/analysis/examples/larger-project/node_modules/rescript/lib/ocaml
-B /Users/cristianocalcagno/GitHub/rescript-vscode/analysis/examples/larger-project/node_modules/rescript/lib/ocaml
+FLG -ppx '/home/pedro/Desktop/Projects/rescript-vscode/analysis/examples/larger-project/node_modules/rescript/linux/bsc.exe -as-ppx -bs-jsx 3'
+S /home/pedro/Desktop/Projects/rescript-vscode/analysis/examples/larger-project/node_modules/rescript/lib/ocaml
+B /home/pedro/Desktop/Projects/rescript-vscode/analysis/examples/larger-project/node_modules/rescript/lib/ocaml
 FLG -w +a-4-9-20-40-41-42-50-61-102
-S /Users/cristianocalcagno/GitHub/rescript-vscode/analysis/examples/larger-project/node_modules/@rescript/react/lib/ocaml
-B /Users/cristianocalcagno/GitHub/rescript-vscode/analysis/examples/larger-project/node_modules/@rescript/react/lib/ocaml
-S /Users/cristianocalcagno/GitHub/rescript-vscode/analysis/examples/larger-project/node_modules/@glennsl/bs-json/lib/ocaml
-B /Users/cristianocalcagno/GitHub/rescript-vscode/analysis/examples/larger-project/node_modules/@glennsl/bs-json/lib/ocaml
+S /home/pedro/Desktop/Projects/rescript-vscode/analysis/examples/larger-project/node_modules/@rescript/react/lib/ocaml
+B /home/pedro/Desktop/Projects/rescript-vscode/analysis/examples/larger-project/node_modules/@rescript/react/lib/ocaml
+S /home/pedro/Desktop/Projects/rescript-vscode/analysis/examples/larger-project/node_modules/@glennsl/bs-json/lib/ocaml
+B /home/pedro/Desktop/Projects/rescript-vscode/analysis/examples/larger-project/node_modules/@glennsl/bs-json/lib/ocaml
 S src
 B lib/bs/src
 S src/exception

analysis/src/Cli.ml

@@ -11,6 +11,7 @@ API examples:
   ./rescript-editor-analysis.exe references src/MyFile.res 10 2
   ./rescript-editor-analysis.exe rename src/MyFile.res 10 2 foo
   ./rescript-editor-analysis.exe diagnosticSyntax src/MyFile.res
+  /rescript-editor-analysis.exe inlayHint src/MyFile.res 0 3 25
 
 Dev-time examples:
   ./rescript-editor-analysis.exe dump src/MyFile.res src/MyFile2.res
@@ -65,6 +66,10 @@ Options:
 
     ./rescript-editor-analysis.exe diagnosticSyntax src/MyFile.res
 
+  inlayHint: get all inlay Hint between line 0 and 3 declared in MyFile.res. Last argument is maximum of character length for inlay hints
+
+    ./rescript-editor-analysis.exe inlayHint src/MyFile.res 0 3 25
+
   test: run tests specified by special comments in file src/MyFile.res
 
     ./rescript-editor-analysis.exe test src/src/MyFile.res
@@ -89,6 +94,10 @@ let main () =
     Commands.hover ~path
       ~pos:(int_of_string line, int_of_string col)
       ~currentFile ~debug:false
+  | [_; "inlayHint"; path; line_start; line_end; maxLength] ->
+    Commands.inlayhint ~path
+      ~pos:(int_of_string line_start, int_of_string line_end)
+      ~maxLength ~debug:false
   | [_; "codeAction"; path; line; col; currentFile] ->
     Commands.codeAction ~path
       ~pos:(int_of_string line, int_of_string col)

analysis/src/Commands.ml

@@ -28,6 +28,10 @@ let completion ~debug ~path ~pos ~currentFile =
     |> List.map Protocol.stringifyCompletionItem
     |> Protocol.array)
 
+let inlayhint ~path ~pos ~maxLength ~debug =
+  let result = Hint.inlay ~path ~pos ~maxLength ~debug |> Protocol.array in
+  print_endline result
+
 let hover ~path ~pos ~currentFile ~debug =
   let result =
     match Cmt.fullFromPath ~path with
@@ -382,6 +386,11 @@ let test ~path =
                                    (Protocol.stringifyRange range)
                                    indent indent newText)))
           | "dia" -> diagnosticSyntax ~path
+          | "hin" -> (
+            let line_start = 0 in
+            let line_end = 6 in
+            print_endline ("Inlay Hint " ^ path ^ " " ^ string_of_int line_start ^ ":" ^ string_of_int line_end);
+            inlayhint ~path ~pos:(line_start, line_end) ~maxLength:"25" ~debug:false)
           | _ -> ());
           print_newline ())
     in

analysis/src/Hint.ml

@@ -0,0 +1,122 @@
+open SharedTypes
+
+type inlayHintKind = Type | Parameter
+let inlayKindToNumber = function
+  | Type -> 1
+  | Parameter -> 2
+
+let locItemToTypeHint ~full:{file; package} locItem =
+  match locItem.locType with
+  | Constant t ->
+    Some
+      (match t with
+      | Const_int _ -> "int"
+      | Const_char _ -> "char"
+      | Const_string _ -> "string"
+      | Const_float _ -> "float"
+      | Const_int32 _ -> "int32"
+      | Const_int64 _ -> "int64"
+      | Const_nativeint _ -> "int")
+  | Typed (_, t, locKind) ->
+    let fromType typ =
+      typ |> Shared.typeToString
+      |> Str.global_replace (Str.regexp "[\r\n\t]") ""
+    in
+    Some
+      (match References.definedForLoc ~file ~package locKind with
+      | None -> fromType t
+      | Some (_, res) -> (
+        match res with
+        | `Declared -> fromType t
+        | `Constructor _ -> fromType t
+        | `Field -> fromType t))
+  | _ -> None
+
+let inlay ~path ~pos ~maxLength ~debug =
+  let maxlen = try Some (int_of_string maxLength) with Failure _ -> None in
+  let hints = ref [] in
+  let start_line, end_line = pos in
+  let push loc kind =
+    let range = Utils.cmtLocToRange loc in
+    if start_line <= range.end_.line && end_line >= range.start.line then
+      hints := (range, kind) :: !hints
+  in
+  let rec processFunction (exp : Parsetree.expression) =
+    match exp.pexp_desc with
+    | Pexp_fun (_, _, pat_exp, e) -> (
+      match pat_exp with
+      | {ppat_desc = Ppat_var _} ->
+        push pat_exp.ppat_loc Type;
+        processFunction e
+      | _ -> processFunction e)
+    | _ -> ()
+  in
+  let value_binding (iterator : Ast_iterator.iterator)
+      (vb : Parsetree.value_binding) =
+    (match vb with
+    | {
+     pvb_pat = {ppat_desc = Ppat_var _};
+     pvb_expr =
+       {
+         pexp_desc =
+           ( Pexp_constant _ | Pexp_tuple _ | Pexp_record _ | Pexp_variant _
+           | Pexp_apply _ | Pexp_match _ | Pexp_construct _ | Pexp_ifthenelse _
+           | Pexp_array _ | Pexp_ident _ | Pexp_try _ | Pexp_lazy _
+           | Pexp_send _ | Pexp_field _ | Pexp_open _ );
+       };
+    } ->
+      push vb.pvb_pat.ppat_loc Type
+    | {pvb_pat = {ppat_desc = Ppat_tuple tuples}} ->
+      List.iter
+        (fun (tuple : Parsetree.pattern) -> push tuple.ppat_loc Type)
+        tuples
+    | {
+     pvb_pat = {ppat_desc = Ppat_var _};
+     pvb_expr = {pexp_desc = Pexp_fun (_, _, pat, e)};
+    } ->
+      (match pat with
+      | {ppat_desc = Ppat_var _} -> push pat.ppat_loc Type
+      | _ -> ());
+      processFunction e
+    | _ -> ());
+    Ast_iterator.default_iterator.value_binding iterator vb
+  in
+  let iterator = {Ast_iterator.default_iterator with value_binding} in
+  (if Filename.check_suffix path ".res" then
+   let parser =
+     Res_driver.parsingEngine.parseImplementation ~forPrinter:false
+   in
+   let {Res_driver.parsetree = structure} = parser ~filename:path in
+   iterator.structure iterator structure |> ignore);
+  !hints
+  |> List.filter_map (fun ((range : Protocol.range), hintKind) ->
+         match Cmt.fullFromPath ~path with
+         | None -> None
+         | Some full -> (
+           match
+             References.getLocItem ~full
+               ~pos:(range.start.line, range.start.character + 1)
+               ~debug
+           with
+           | None -> None
+           | Some locItem -> (
+             let position : Protocol.position =
+               {line = range.start.line; character = range.end_.character}
+             in
+             match locItemToTypeHint locItem ~full with
+             | Some label -> (
+               let result =
+                 Protocol.stringifyHint
+                   {
+                     kind = inlayKindToNumber hintKind;
+                     position;
+                     paddingLeft = true;
+                     paddingRight = false;
+                     label = ": " ^ label;
+                   }
+               in
+               match maxlen with
+               | Some value ->
+                 if String.length label > value then None else Some result
+               | None -> Some result)
+             | None -> None)))

analysis/src/Protocol.ml

@@ -1,6 +1,13 @@
 type position = {line: int; character: int}
 type range = {start: position; end_: position}
 type markupContent = {kind: string; value: string}
+type inlayHint = {
+  position: position;
+  label: string;
+  kind: int;
+  paddingLeft: bool;
+  paddingRight: bool;
+}
 
 type completionItem = {
   label: string;
@@ -128,6 +135,18 @@ let stringifyCodeAction ca =
     (codeActionKindToString ca.codeActionKind)
     (ca.edit |> stringifyCodeActionEdit)
 
+let stringifyHint hint =
+  Printf.sprintf
+    {|{
+    "position": %s,
+    "label": "%s",
+    "kind": %i,
+    "paddingLeft": %b,
+    "paddingRight": %b
+}|}
+    (stringifyPosition hint.position)
+    (Json.escape hint.label) hint.kind hint.paddingLeft hint.paddingRight
+
 (* https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#diagnostic *)
 let stringifyDiagnostic d =
   Printf.sprintf

analysis/tests/src/InlayHint.res

@@ -0,0 +1,20 @@
+let string = "ReScript"
+let number = 1
+let float = 1.1
+let char = 'c'
+
+let add = (x, y) => x + y
+
+let my_sum = 3->add(1)->add(1)->add(1)->add(8)
+
+let withAs = (~xx as yyy) => yyy + 1
+
+
+@react.component
+let make = (~name) => React.string(name)
+
+let tuple = ("ReScript", "lol")
+
+let (lang, _) = tuple
+
+//^hin

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

@@ -1,3 +1,3 @@
 DCE src/Dce.res
-issues:235
+issues:243
 

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

@@ -4,7 +4,7 @@ Dependencies: @rescript/react
 Source directories: ./node_modules/@rescript/react/src ./node_modules/@rescript/react/src/legacy
 Source files: ./node_modules/@rescript/react/src/React.res ./node_modules/@rescript/react/src/ReactDOM.res ./node_modules/@rescript/react/src/ReactDOMServer.res ./node_modules/@rescript/react/src/ReactDOMStyle.res ./node_modules/@rescript/react/src/ReactEvent.res ./node_modules/@rescript/react/src/ReactEvent.resi ./node_modules/@rescript/react/src/ReactTestUtils.res ./node_modules/@rescript/react/src/ReactTestUtils.resi ./node_modules/@rescript/react/src/RescriptReactErrorBoundary.res ./node_modules/@rescript/react/src/RescriptReactErrorBoundary.resi ./node_modules/@rescript/react/src/RescriptReactRouter.res ./node_modules/@rescript/react/src/RescriptReactRouter.resi ./node_modules/@rescript/react/src/legacy/ReactDOMRe.res ./node_modules/@rescript/react/src/legacy/ReasonReact.res
 Source directories: ./src ./src/expected
-Source files: ./src/Auto.res ./src/CompletePrioritize1.res ./src/CompletePrioritize2.res ./src/Completion.res ./src/Component.res ./src/Component.resi ./src/CreateInterface.res ./src/Cross.res ./src/Dce.res ./src/Debug.res ./src/Definition.res ./src/DefinitionWithInterface.res ./src/DefinitionWithInterface.resi ./src/Div.res ./src/DocumentSymbol.res ./src/Fragment.res ./src/Highlight.res ./src/Hover.res ./src/Jsx.res ./src/Jsx.resi ./src/LongIdentTest.res ./src/Object.res ./src/Patterns.res ./src/RecModules.res ./src/RecordCompletion.res ./src/RecoveryOnProp.res ./src/References.res ./src/ReferencesWithInterface.res ./src/ReferencesWithInterface.resi ./src/Rename.res ./src/RenameWithInterface.res ./src/RenameWithInterface.resi ./src/TableclothMap.ml ./src/TableclothMap.mli ./src/TypeDefinition.res ./src/Xform.res
+Source files: ./src/Auto.res ./src/CompletePrioritize1.res ./src/CompletePrioritize2.res ./src/Completion.res ./src/Component.res ./src/Component.resi ./src/CreateInterface.res ./src/Cross.res ./src/Dce.res ./src/Debug.res ./src/Definition.res ./src/DefinitionWithInterface.res ./src/DefinitionWithInterface.resi ./src/Div.res ./src/DocumentSymbol.res ./src/Fragment.res ./src/Highlight.res ./src/Hover.res ./src/InlayHint.res ./src/Jsx.res ./src/Jsx.resi ./src/LongIdentTest.res ./src/Object.res ./src/Patterns.res ./src/RecModules.res ./src/RecordCompletion.res ./src/RecoveryOnProp.res ./src/References.res ./src/ReferencesWithInterface.res ./src/ReferencesWithInterface.resi ./src/Rename.res ./src/RenameWithInterface.res ./src/RenameWithInterface.resi ./src/TableclothMap.ml ./src/TableclothMap.mli ./src/TypeDefinition.res ./src/Xform.res
 Impl cmt:./lib/bs/src/Auto.cmt res:./src/Auto.res
 Impl cmt:./lib/bs/src/CompletePrioritize1.cmt res:./src/CompletePrioritize1.res
 Impl cmt:./lib/bs/src/CompletePrioritize2.cmt res:./src/CompletePrioritize2.res
@@ -21,6 +21,7 @@ Impl cmt:./lib/bs/src/DocumentSymbol.cmt res:./src/DocumentSymbol.res
 Impl cmt:./lib/bs/src/Fragment.cmt res:./src/Fragment.res
 Impl cmt:./lib/bs/src/Highlight.cmt res:./src/Highlight.res
 Impl cmt:./lib/bs/src/Hover.cmt res:./src/Hover.res
+Impl cmt:./lib/bs/src/InlayHint.cmt res:./src/InlayHint.res
 IntfAndImpl cmti:./lib/bs/src/Jsx.cmti resi:./src/Jsx.resi cmt:./lib/bs/src/Jsx.cmt res:./src/Jsx.res
 Impl cmt:./lib/bs/src/LongIdentTest.cmt res:./src/LongIdentTest.res
 Impl cmt:./lib/bs/src/Object.cmt res:./src/Object.res

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

@@ -0,0 +1,39 @@
+Inlay Hint src/InlayHint.res 0:6
+[{
+    "position": {"line": 5, "character": 15},
+    "label": ": int",
+    "kind": 1,
+    "paddingLeft": true,
+    "paddingRight": false
+}, {
+    "position": {"line": 5, "character": 12},
+    "label": ": int",
+    "kind": 1,
+    "paddingLeft": true,
+    "paddingRight": false
+}, {
+    "position": {"line": 3, "character": 8},
+    "label": ": char",
+    "kind": 1,
+    "paddingLeft": true,
+    "paddingRight": false
+}, {
+    "position": {"line": 2, "character": 9},
+    "label": ": float",
+    "kind": 1,
+    "paddingLeft": true,
+    "paddingRight": false
+}, {
+    "position": {"line": 1, "character": 10},
+    "label": ": int",
+    "kind": 1,
+    "paddingLeft": true,
+    "paddingRight": false
+}, {
+    "position": {"line": 0, "character": 10},
+    "label": ": string",
+    "kind": 1,
+    "paddingLeft": true,
+    "paddingRight": false
+}]
+

client/src/extension.ts

@@ -235,6 +235,17 @@ export function activate(context: ExtensionContext) {
   // Start the client. This will also launch the server
   client.start();
 
+  // Restart the language client automatically when certain configuration
+  // changes. These are typically settings that affect the capabilities of the
+  // language client, and because of that requires a full restart.
+  context.subscriptions.push(
+    workspace.onDidChangeConfiguration(({ affectsConfiguration }) => {
+      if (affectsConfiguration("rescript.settings.inlayHints")) {
+        commands.executeCommand("rescript-vscode.restart_language_server");
+      }
+    })
+  );
+
   // Autostart code analysis if wanted
   if (
     workspace

package.json

@@ -132,6 +132,20 @@
 					"default": false,
 					"description": "Automatically start ReScript's code analysis."
 				},
+				"rescript.settings.inlayHints.enable": {
+					"type": "boolean",
+					"default": false,
+					"description": "Enable (experimental) inlay hints."
+				},
+				"rescript.settings.inlayHints.maxLength": {
+					"markdownDescription": "Maximum length of character for inlay hints. Set to null to have an unlimited length. Inlay hints that exceed the maximum length will not be shown.",
+                    "default": 25,
+                    "type": [
+                        "null",
+                        "integer"
+                    ],
+                    "minimum": 0
+				},
 				"rescript.settings.binaryPath": {
 					"type": ["string", "null"],
 					"default": null,