handle optional args as well

Author: ulugbekna

ocaml-lsp-server/src/compl.ml

@@ -31,7 +31,7 @@ let completion_kind kind : CompletionItemKind.t option =
 let prefix_of_position ~short_path source position =
   match Msource.text source with
   | "" -> ""
-  | text -> (
+  | text ->
     let from =
       let (`Offset index) = Msource.get_offset source position in
       min (String.length text - 1) (index - 1)
@@ -89,13 +89,17 @@ let prefix_of_position ~short_path source position =
     in
     let len = from - pos + 1 in
     let reconstructed_prefix = String.sub text ~pos ~len in
-    (* if we reconstructed [~f:ignore], we should take only [ignore], so: *)
-    if not (String.is_prefix reconstructed_prefix ~prefix:"~") then
-      reconstructed_prefix
-    else
+    (* if we reconstructed [~f:ignore] or [?f:ignore], we should take only
+       [ignore], so: *)
+    if
+      String.is_prefix reconstructed_prefix ~prefix:"~"
+      || String.is_prefix reconstructed_prefix ~prefix:"?"
+    then
       match String.lsplit2 reconstructed_prefix ~on:':' with
       | Some (_, s) -> s
-      | None -> reconstructed_prefix)
+      | None -> reconstructed_prefix
+    else
+      reconstructed_prefix
 
 let suffix_of_position source position =
   match Msource.text source with

ocaml-lsp-server/test/e2e/__tests__/textDocument-completion.test.ts

@@ -136,6 +136,65 @@ g ~f:M.ig
     `);
   });
 
+  it("can complete symbol passed as an optional argument", async () => {
+    await openDocument(outdent`
+let g ?f = f in
+g ?f:ig
+    `);
+
+    let items = await queryCompletion(Types.Position.create(1, 7));
+    expect(items).toMatchInlineSnapshot(`
+      Array [
+        Object {
+          "label": "ignore",
+          "textEdit": Object {
+            "newText": "ignore",
+            "range": Object {
+              "end": Object {
+                "character": 7,
+                "line": 1,
+              },
+              "start": Object {
+                "character": 5,
+                "line": 1,
+              },
+            },
+          },
+        },
+      ]
+    `);
+  });
+
+  it("can complete symbol passed as a optional argument - 2", async () => {
+    await openDocument(outdent`
+module M = struct let igfoo _x = () end
+let g ?f = f in
+g ?f:M.ig
+    `);
+
+    let items = await queryCompletion(Types.Position.create(2, 9));
+    expect(items).toMatchInlineSnapshot(`
+      Array [
+        Object {
+          "label": "igfoo",
+          "textEdit": Object {
+            "newText": "igfoo",
+            "range": Object {
+              "end": Object {
+                "character": 9,
+                "line": 2,
+              },
+              "start": Object {
+                "character": 7,
+                "line": 2,
+              },
+            },
+          },
+        },
+      ]
+    `);
+  });
+
   it("completes identifier at top level", async () => {
     await openDocument(outdent`
       let somenum = 42