Prioritize non-ghost nodes when looking for best node. (ocaml#1664)

from voodoos/issue1660 Fixes ocaml#1660

CHANGES.md

@@ -14,6 +14,7 @@ unreleased
     - Fix construct not working with inline records (#1658)
     - Improve behavior of `type-enclosing` on let/and operators (#1653)
     - Fix occurrences of extension constructors (#1662)
+    - Improve node selection when ghosts are present (#1664, fixes #1660)
   + editor modes
     - emacs: call merlin-client-logger with "interrupted" if the
       merlin binary itself is interrupted, not just the parsing of the

src/kernel/mbrowse.ml

@@ -123,6 +123,9 @@ let compare_locations pos l1 l2 =
   with
   | 0, 0 ->
     (* Cursor inside both locations: favor closer to the end *)
+    if l1.Location.loc_ghost then 1
+    else if l2.Location.loc_ghost then -1
+    else
     Lexing.compare_pos l1.Location.loc_end l2.Location.loc_end
   (* Cursor inside one location: it has priority *)
   | 0, _ -> t1_first

tests/test-dirs/with-ppx/dune

@@ -1,3 +1,7 @@
 (cram
  (applies_to :whole_subtree)
  (locks ../server-tests/merlin_server))
+
+(cram
+ (applies_to issue1660-deriving-compare)
+ (enabled_if (= %{env:MERLIN_TESTS=default} all)))

tests/test-dirs/with-ppx/issue1660-deriving-compare.t

@@ -0,0 +1,36 @@
+  $ cat >dune-project <<EOF
+  > (lang dune 2.0)
+  > EOF
+
+  $ cat >main.ml <<EOF
+  > module M = struct
+  >   type t =
+  >     | Foo
+  >     | Bar
+  > end
+  > EOF
+
+  $ $MERLIN single type-enclosing -position 2:7 \
+  > -filename main.ml < main.ml |  jq '.value[0].type'
+  "type t = Foo | Bar"
+
+
+  $ cat >main.ml <<EOF
+  > module M = struct
+  >   type t =
+  >     | Foo
+  >     | Bar
+  >   [@@deriving compare]
+  > end
+  > EOF
+
+  $ cat >dune <<EOF
+  > (library
+  >  (name main)
+  >  (preprocess (pps ppx_compare)))
+
+  $ dune build
+
+  $ $MERLIN single type-enclosing -position 2:7 \
+  > -filename main.ml < main.ml |  jq '.value[0].type'
+  "type t =o | Bar"