Support LSP function parameter auto-completion.

src/common/flow_lsp_conversions.ml

@@ -18,31 +18,35 @@ let flow_completion_to_lsp
     let params = Core_list.map ~f:(fun p -> p.param_name ^ ": " ^ p.param_ty) params in
     "(" ^ (String.concat ", " params) ^ ")"
   in
-  let kind, itemType, inlineDetail, detail = match item.func_details with
+  let flow_params_to_lsp_snippet name params =
+    let params = Core_list.mapi ~f:(fun i p -> "${" ^ string_of_int (i +1 ) ^ ":" ^ p.param_name ^ "}") params in
+      name ^ "(" ^ (String.concat ", " params) ^ ")"
+  in
+  let kind, itemType, inlineDetail, detail, insertText, insertTextFormat, label = match item.func_details with
     | Some func_details ->
       let kind = Some Function in
       let itemType = Some (trunc 30 func_details.return_ty) in
       let inlineDetail = Some (trunc 40 (flow_params_to_string func_details.param_tys)) in
       let detail = Some (trunc80 item.res_ty) in
-      kind, itemType, inlineDetail, detail
+      kind, itemType, inlineDetail, detail, Some (flow_params_to_lsp_snippet item.res_name func_details.param_tys), Some SnippetFormat, item.res_name
     | None ->
       let kind = None in
       let itemType = None in
       let inlineDetail = Some (trunc80 item.res_ty) in
       let detail = Some (trunc80 item.res_ty) in
-      kind, itemType, inlineDetail, detail
+      kind, itemType, inlineDetail, detail, None, Some PlainText, item.res_name
   in
   {
-    label = item.res_name;
     kind;
+    label;
     detail = detail;
     inlineDetail;
     itemType;
     documentation = None; (* This will be filled in by completionItem/resolve. *)
     sortText = None;
     filterText = None;
-    insertText = None;
-    insertTextFormat = Some PlainText;
+    insertText;
+    insertTextFormat;
     textEdits = [];
     command = None;
     data = None;