Add prepareRename command

CHANGELOG.md

@@ -38,6 +38,8 @@
 
 #### :house: Internal
 
+- Add a `prepareRename` command the LSP can use for faster renames. https://github.com/rescript-lang/rescript/pull/7847
+
 # 12.0.0-beta.9
 
 #### :boom: Breaking Change

analysis/bin/main.ml

@@ -11,6 +11,7 @@ API examples:
   ./rescript-editor-analysis.exe documentSymbol src/Foo.res
   ./rescript-editor-analysis.exe hover src/MyFile.res 10 2 true
   ./rescript-editor-analysis.exe references src/MyFile.res 10 2
+  ./rescript-editor-analysis.exe prepareRename 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
@@ -49,6 +50,10 @@ Options:
 
     ./rescript-editor-analysis.exe references src/MyFile.res 10 2
 
+  prepareRename: quickly compute the identifier range (and placeholder) for item at line 10 column 2 without scanning references:
+
+    ./rescript-editor-analysis.exe prepareRename src/MyFile.res 10 2
+
   rename: rename all appearances of item in MyFile.res at line 10 column 2 with foo:
 
     ./rescript-editor-analysis.exe rename src/MyFile.res 10 2 foo
@@ -197,6 +202,10 @@ let main () =
     Commands.references ~path
       ~pos:(int_of_string line, int_of_string col)
       ~debug
+  | [_; "prepareRename"; path; line; col] ->
+    Commands.prepareRename ~path
+      ~pos:(int_of_string line, int_of_string col)
+      ~debug
   | [_; "rename"; path; line; col; newName] ->
     Commands.rename ~path
       ~pos:(int_of_string line, int_of_string col)

analysis/src/Commands.ml

@@ -275,6 +275,30 @@ let rename ~path ~pos ~newName ~debug =
   in
   print_endline result
 
+let prepareRename ~path ~pos ~debug =
+  match Cmt.loadFullCmtFromPath ~path with
+  | None -> print_endline Protocol.null
+  | Some full -> (
+    match References.getLocItem ~full ~pos ~debug with
+    | None -> print_endline Protocol.null
+    | Some locItem ->
+      let range = Utils.cmtLocToRange locItem.loc in
+      let placeholderOpt =
+        match locItem.locType with
+        | Typed (name, _, _) | TopLevelModule name | TypeDefinition (name, _, _)
+          ->
+          Some name
+        | _ -> None
+      in
+      let fields =
+        [("range", Some (Protocol.stringifyRange range))]
+        @
+        match placeholderOpt with
+        | None -> []
+        | Some s -> [("placeholder", Some (Protocol.wrapInQuotes s))]
+      in
+      print_endline (Protocol.stringifyObject fields))
+
 let format ~path =
   if Filename.check_suffix path ".res" then
     let {Res_driver.parsetree = structure; comments; diagnostics} =
@@ -415,6 +439,11 @@ let test ~path =
               ("References " ^ path ^ " " ^ string_of_int line ^ ":"
              ^ string_of_int col);
             references ~path ~pos:(line, col) ~debug:true
+          | "pre" ->
+            print_endline
+              ("PrepareRename " ^ path ^ " " ^ string_of_int line ^ ":"
+             ^ string_of_int col);
+            prepareRename ~path ~pos:(line, col) ~debug:true
           | "ren" ->
             let newName = String.sub rest 4 (len - mlen - 4) in
             let () =

tests/analysis_tests/tests/src/PrepareRename.res

@@ -0,0 +1,6 @@
+let x = 12
+//  ^pre
+
+let foo = (~xx) => xx + 1
+//                 ^pre
+

tests/analysis_tests/tests/src/expected/PrepareRename.res.txt

@@ -0,0 +1,12 @@
+PrepareRename src/PrepareRename.res 0:4
+{
+    "range": {"start": {"line": 0, "character": 4}, "end": {"line": 0, "character": 5}},
+    "placeholder": "x"
+  }
+
+PrepareRename src/PrepareRename.res 3:19
+{
+    "range": {"start": {"line": 3, "character": 19}, "end": {"line": 3, "character": 21}},
+    "placeholder": "xx"
+  }
+