Completion for in keyword (ocaml#1217)

feat(auto-completion): auto-complete `in` (in a hacky way) in .ml files

CHANGES.md

@@ -27,6 +27,8 @@
 - Add mark/remove unused actions for open, types, for loop indexes, modules,
   match cases, rec, and constructors (#1141)
 
+- Offer auto-completion for the keyword `in` (#1217)
+
 # 1.16.2
 
 ## Fixes

ocaml-lsp-server/src/compl.ml

@@ -158,6 +158,23 @@ module Complete_by_prefix = struct
       completion_entries
       ~f:(completionItem_of_completion_entry ~deprecated ~range ~compl_params)
 
+  let complete_keywords completion_position prefix =
+    match prefix with
+    | "" | "i" | "in" ->
+      let ci_for_in =
+        CompletionItem.create
+          ~label:"in"
+          ~textEdit:
+            (`TextEdit
+              (TextEdit.create
+                 ~newText:"in"
+                 ~range:(range_prefix completion_position prefix)))
+          ~kind:CompletionItemKind.Keyword
+          ()
+      in
+      [ ci_for_in ]
+    | _ -> []
+
   let complete doc prefix pos ~deprecated ~resolve =
     let+ (completion : Query_protocol.completions) =
       let logical_pos = Position.logical pos in
@@ -166,7 +183,14 @@ module Complete_by_prefix = struct
         doc
         (dispatch_cmd ~prefix logical_pos)
     in
-    process_dispatch_resp ~deprecated ~resolve doc pos completion
+    let keyword_completionItems =
+      (* we complete only keyword 'in' for now *)
+      match Document.Merlin.kind doc with
+      | Intf -> []
+      | Impl -> complete_keywords pos prefix
+    in
+    keyword_completionItems
+    @ process_dispatch_resp ~deprecated ~resolve doc pos completion
 end
 
 module Complete_with_construct = struct

ocaml-lsp-server/test/e2e-new/completion.ml

@@ -595,6 +595,17 @@ let plus_42 (x:int) (y:int) =
   [%expect
     {|
   Completions:
+  {
+    "kind": 14,
+    "label": "in",
+    "textEdit": {
+      "newText": "in",
+      "range": {
+        "end": { "character": 12, "line": 5 },
+        "start": { "character": 12, "line": 5 }
+      }
+    }
+  }
   {
     "detail": "int",
     "kind": 12,
@@ -712,19 +723,6 @@ let plus_42 (x:int) (y:int) =
       }
     }
   }
-  {
-    "detail": "char -> int",
-    "kind": 12,
-    "label": "int_of_char",
-    "sortText": "0009",
-    "textEdit": {
-      "newText": "int_of_char",
-      "range": {
-        "end": { "character": 12, "line": 5 },
-        "start": { "character": 12, "line": 5 }
-      }
-    }
-  }
   .............
   |}]
 
@@ -1162,3 +1160,149 @@ let%expect_test "completion doesn't autocomplete record fields" =
 
   (* We expect 0 completions*)
   [%expect {| No completions |}]
+
+let%expect_test "completion for `in` keyword - no prefix" =
+  let source = {ocaml|
+let foo param1 =
+  let bar = param1 |ocaml} in
+  let position = Position.create ~line:2 ~character:19 in
+  print_completions ~limit:3 source position;
+  [%expect
+    {|
+    Completions:
+    {
+      "kind": 14,
+      "label": "in",
+      "textEdit": {
+        "newText": "in",
+        "range": {
+          "end": { "character": 19, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    {
+      "detail": "'a -> 'b",
+      "kind": 12,
+      "label": "param1",
+      "sortText": "0000",
+      "textEdit": {
+        "newText": "param1",
+        "range": {
+          "end": { "character": 19, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    {
+      "detail": "'a ref -> 'a",
+      "kind": 12,
+      "label": "!",
+      "sortText": "0001",
+      "textEdit": {
+        "newText": "!",
+        "range": {
+          "end": { "character": 19, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    ............. |}]
+
+let%expect_test "completion for `in` keyword - prefix i" =
+  let source = {ocaml|
+let foo param1 =
+  let bar = param1 i
+|ocaml} in
+  let position = Position.create ~line:2 ~character:20 in
+  print_completions ~limit:3 source position;
+  [%expect
+    {|
+    Completions:
+    {
+      "kind": 14,
+      "label": "in",
+      "textEdit": {
+        "newText": "in",
+        "range": {
+          "end": { "character": 20, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    {
+      "detail": "'a -> unit",
+      "kind": 12,
+      "label": "ignore",
+      "sortText": "0000",
+      "textEdit": {
+        "newText": "ignore",
+        "range": {
+          "end": { "character": 20, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    {
+      "detail": "in_channel -> int",
+      "kind": 12,
+      "label": "in_channel_length",
+      "sortText": "0001",
+      "textEdit": {
+        "newText": "in_channel_length",
+        "range": {
+          "end": { "character": 20, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    ............. |}]
+
+let%expect_test "completion for `in` keyword - prefix in" =
+  let source = {ocaml|
+let foo param1 =
+  let bar = param1 in
+|ocaml} in
+  let position = Position.create ~line:2 ~character:21 in
+  print_completions ~limit:3 source position;
+  [%expect
+    {|
+    Completions:
+    {
+      "kind": 14,
+      "label": "in",
+      "textEdit": {
+        "newText": "in",
+        "range": {
+          "end": { "character": 21, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    {
+      "detail": "in_channel -> int",
+      "kind": 12,
+      "label": "in_channel_length",
+      "sortText": "0000",
+      "textEdit": {
+        "newText": "in_channel_length",
+        "range": {
+          "end": { "character": 21, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    {
+      "detail": "int ref -> unit",
+      "kind": 12,
+      "label": "incr",
+      "sortText": "0001",
+      "textEdit": {
+        "newText": "incr",
+        "range": {
+          "end": { "character": 21, "line": 2 },
+          "start": { "character": 19, "line": 2 }
+        }
+      }
+    }
+    ............. |}]