Signature help

README.md

@@ -68,6 +68,7 @@ The only 2 themes we don't (and can't) support, due to their lack of coloring, a
 - Find references.
 - Rename.
 - Inlay Hints.
+- Signature help.
 - Code lenses.
 - Snippets to ease a few syntaxes:
   - `external` features such as `@bs.module` and `@bs.val`
@@ -85,14 +86,15 @@ ext install chenglou92.rescript-vscode
 The plugin activates on `.res` and `.resi` files. If you've already got Reason-Language-Server installed, it's possible that the latter took precedence over this one. Make sure you're using this plugin ("ReScript syntax") rather than Reason-Language-Server ("BuckleScript syntax").
 
 ### Pre-release channel
+
 There is a pre-release channel available. It is intended for testing new and therefore possibly unstable features. You can activate it by clicking on the "Switch to Pre-Release Version" button on the `rescript-vscode` extension page in VSCode. From this point on, pre-release versions will always have an odd version minor (1.5.x, 1.7.x, 2.1.x, etc.) while stable releases have even version minor numbers (1.4.x, 1.6.x, 2.0.0, etc.).
 
 Even if the pre-release channel seems too experimental to you, we still suggest you to give it a try and submit any issues that you run into. In the long run it will give us a better editor experience overall.
 
 ## 📦 Commands
 
 | Command                                                          | Description                                                                                                                                                                                                                                                                                           |
-|------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| ---------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
 | ReScript: Create an interface file for this implementation file  | Creates an interface file (`.resi`) for the current `.res` file, automatically filling in all types and values in the current file.                                                                                                                                                                   |
 | ReScript: Open the compiled JS file for this implementation file | Opens the compiled JS file for the current ReScript file.                                                                                                                                                                                                                                             |
 | ReScript: Switch implementation/interface                        | Switches between the implementation and interface file. If you're in a `.res` file, the command will open the corresponding `.resi` file (if it exists), and if you're in a `.resi` file the command will open the corresponding `.res` file. This can also be triggered with the keybinding `Alt+O`. |
@@ -104,10 +106,10 @@ You'll find all ReScript specific settings under the scope `rescript.settings`.
 
 | Setting                        | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
 | ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
-| Prompt to Start Build  | If there's no ReScript build running already in the opened project, the extension will prompt you and ask if you want to start a build automatically. You can turn off this automatic prompt via the setting `rescript.settings.askToStartBuild`.                                                                                                                                                                                                                                    |
+| Prompt to Start Build          | If there's no ReScript build running already in the opened project, the extension will prompt you and ask if you want to start a build automatically. You can turn off this automatic prompt via the setting `rescript.settings.askToStartBuild`.                                                                                                                                                                                                                                    |
 | ReScript Binary Path           | The extension will look for the existence of a `/node_modules/.bin/rescript` file and use its directory as the `binaryPath`. If it does not find it at the project root (which is where the nearest `bsconfig.json` resides), it goes up folders in the filesystem recursively until it either finds it (often the case in monorepos) or hits the top level. 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. Enable using `rescript.settings.inlayHints.enable: true` |
-| Code Lens (experimental) | This tells the editor to add code lenses to function definitions, showing its full type above the definition. Enable using `rescript.settings.codeLens: true` |
+| Inlay Hints (experimental)     | This allows an editor to place annotations inline with text to display type hints. Enable using `rescript.settings.inlayHints.enable: true`                                                                                                                                                                                                                                                                                                                                          |
+| Code Lens (experimental)       | This tells the editor to add code lenses to function definitions, showing its full type above the definition. Enable using `rescript.settings.codeLens: true`                                                                                                                                                                                                                                                                                                                        |
 | Autostarting the Code Analyzer | The Code Analyzer needs to be started manually by default. However, you can configure the extension to start the Code Analyzer automatically via the setting `rescript.settings.autoRunCodeAnalysis`.                                                                                                                                                                                                                                                                                |
 
 **Default settings:**

analysis/src/Cli.ml

@@ -75,6 +75,10 @@ Options:
 
     ./rescript-editor-analysis.exe codeLens src/MyFile.res
 
+  signatureHelp: get signature help if available for position at line 10 column 2 in src/MyFile.res
+
+    ./rescript-editor-analysis.exe signatureHelp src/MyFile.res 10 2
+
   test: run tests specified by special comments in file src/MyFile.res
 
     ./rescript-editor-analysis.exe test src/src/MyFile.res
@@ -99,6 +103,10 @@ let main () =
     Commands.hover ~path
       ~pos:(int_of_string line, int_of_string col)
       ~currentFile ~debug:false
+  | [_; "signatureHelp"; path; line; col; currentFile] ->
+    Commands.signatureHelp ~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)

analysis/src/Commands.ml

@@ -88,6 +88,15 @@ let hover ~path ~pos ~currentFile ~debug =
   in
   print_endline result
 
+let signatureHelp ~path ~pos ~currentFile ~debug =
+  let result =
+    match SignatureHelp.signatureHelp ~path ~pos ~currentFile ~debug with
+    | None ->
+      {Protocol.signatures = []; activeSignature = None; activeParameter = None}
+    | Some res -> res
+  in
+  print_endline (Protocol.stringifySignatureHelp result)
+
 let codeAction ~path ~pos ~currentFile ~debug =
   Xform.extractCodeActions ~path ~pos ~currentFile ~debug
   |> CodeActions.stringifyCodeActions |> print_endline
@@ -343,6 +352,13 @@ let test ~path =
             let currentFile = createCurrentFile () in
             hover ~path ~pos:(line, col) ~currentFile ~debug:true;
             Sys.remove currentFile
+          | "she" ->
+            print_endline
+              ("Signature help " ^ path ^ " " ^ string_of_int line ^ ":"
+             ^ string_of_int col);
+            let currentFile = createCurrentFile () in
+            signatureHelp ~path ~pos:(line, col) ~currentFile ~debug:true;
+            Sys.remove currentFile
           | "int" ->
             print_endline ("Create Interface " ^ path);
             let cmiFile =

analysis/src/Files.ml

@@ -102,3 +102,9 @@ let classifySourceFile path =
   if Filename.check_suffix path ".res" && exists path then Res
   else if Filename.check_suffix path ".resi" && exists path then Resi
   else Other
+
+let writeTempFile ~prefix ~suffix contents =
+  let tempFile, outChannel = Filename.open_temp_file prefix suffix in
+  Printf.fprintf outChannel "%s" contents;
+  close_out outChannel;
+  tempFile

analysis/src/Loc.ml

@@ -8,3 +8,5 @@ let toString (loc : t) =
   (if loc.loc_ghost then "__ghost__" else "") ^ (loc |> range |> Range.toString)
 
 let hasPos ~pos loc = start loc <= pos && pos < end_ loc
+
+let hasPosInclusive ~pos loc = start loc <= pos && pos <= end_ loc

analysis/src/Protocol.ml

@@ -16,6 +16,23 @@ type inlayHint = {
   paddingRight: bool;
 }
 
+(* https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#parameterInformation *)
+type parameterInformation = {label: int * int}
+
+(* https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#signatureInformation *)
+type signatureInformation = {
+  label: string;
+  parameters: parameterInformation list;
+  documentation: markupContent option;
+}
+
+(* https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#signatureHelp *)
+type signatureHelp = {
+  signatures: signatureInformation list;
+  activeSignature: int option;
+  activeParameter: int option;
+}
+
 type completionItem = {
   label: string;
   kind: int;
@@ -170,6 +187,44 @@ let stringifyCodeLens (codeLens : codeLens) =
     | None -> ""
     | Some command -> stringifyCommand command)
 
+let stringifyParameterInformation (parameterInformation : parameterInformation)
+    =
+  Printf.sprintf {|{"label": %s}|}
+    (let line, chr = parameterInformation.label in
+     "[" ^ string_of_int line ^ ", " ^ string_of_int chr ^ "]")
+
+let stringifySignatureInformation (signatureInformation : signatureInformation)
+    =
+  Printf.sprintf
+    {|{
+    "label": "%s",
+    "parameters": %s%s
+  }|}
+    (Json.escape signatureInformation.label)
+    (signatureInformation.parameters
+    |> List.map stringifyParameterInformation
+    |> array)
+    (match signatureInformation.documentation with
+    | None -> ""
+    | Some docs ->
+      Printf.sprintf ",\n    \"documentation\": %s"
+        (stringifyMarkupContent docs))
+
+let stringifySignatureHelp (signatureHelp : signatureHelp) =
+  Printf.sprintf
+    {|{
+  "signatures": %s,
+  "activeSignature": %s,
+  "activeParameter": %s
+}|}
+    (signatureHelp.signatures |> List.map stringifySignatureInformation |> array)
+    (match signatureHelp.activeSignature with
+    | None -> null
+    | Some activeSignature -> activeSignature |> string_of_int)
+    (match signatureHelp.activeParameter with
+    | None -> null
+    | Some activeParameter -> activeParameter |> string_of_int)
+
 (* https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#diagnostic *)
 let stringifyDiagnostic d =
   Printf.sprintf

analysis/src/SharedTypes.ml

@@ -1,3 +1,8 @@
+let str s = if s = "" then "\"\"" else s
+let list l = "[" ^ (l |> List.map str |> String.concat ", ") ^ "]"
+
+let ident i = i |> List.map str |> String.concat "."
+
 type modulePath =
   | File of Uri.t * string
   | NotVisible
@@ -435,8 +440,6 @@ module Completable = struct
         (** E.g. (["M", "Comp"], "id", ["id1", "id2"]) for <M.Comp id1=... id2=... ... id *)
 
   let toString =
-    let str s = if s = "" then "\"\"" else s in
-    let list l = "[" ^ (l |> List.map str |> String.concat ", ") ^ "]" in
     let completionContextToString = function
       | Value -> "Value"
       | Type -> "Type"