3 files changed, 54 insertions, 18 deletions

diff --git a/src/nvim/regexp_nfa.c b/src/nvim/regexp_nfa.c
index 474f3df32a..3f4e12af4a 100644
--- a/src/nvim/regexp_nfa.c
+++ b/src/nvim/regexp_nfa.c
@@ -3893,21 +3893,25 @@ state_in_list (
   return FALSE;
 }
 
-/*
- * Add "state" and possibly what follows to state list ".".
- * Returns "subs_arg", possibly copied into temp_subs.
- */
+// Offset used for "off" by addstate_here().
+#define ADDSTATE_HERE_OFFSET 10
 
+// Add "state" and possibly what follows to state list ".".
+// Returns "subs_arg", possibly copied into temp_subs.
 static regsubs_T *
 addstate (
     nfa_list_T *l,             /* runtime state list */
     nfa_state_T *state,         /* state to update */
     regsubs_T *subs_arg,      /* pointers to subexpressions */
     nfa_pim_T *pim,           /* postponed look-behind match */
-    int off                            /* byte offset, when -1 go to next line */
-)
+    int off_arg)    /* byte offset, when -1 go to next line */
 {
   int subidx;
+  int off = off_arg;
+  int add_here = FALSE;
+  int listindex = 0;
+  int k;
+  int found = FALSE;
   nfa_thread_T        *thread;
   lpos_T save_lpos;
   int save_in_use;
@@ -3920,6 +3924,12 @@ addstate (
   int did_print = FALSE;
 #endif
 
+  if (off_arg <= -ADDSTATE_HERE_OFFSET) {
+    add_here = true;
+    off = 0;
+    listindex = -(off_arg + ADDSTATE_HERE_OFFSET);
+  }
+
   switch (state->c) {
   case NFA_NCLOSE:
   case NFA_MCLOSE:
@@ -3996,13 +4006,28 @@ addstate (
        * lower position is preferred. */
       if (!nfa_has_backref && pim == NULL && !l->has_pim
           && state->c != NFA_MATCH) {
+
+        /* When called from addstate_here() do insert before
+         * existing states. */
+        if (add_here) {
+          for (k = 0; k < l->n && k < listindex; ++k) {
+            if (l->t[k].state->id == state->id) {
+              found = TRUE;
+              break;
+            }
+          }
+        }
+
+        if (!add_here || found) {
 skip_add:
 #ifdef REGEXP_DEBUG
-        nfa_set_code(state->c);
-        fprintf(log_fd, "> Not adding state %d to list %d. char %d: %s\n",
-            abs(state->id), l->id, state->c, code);
+          nfa_set_code(state->c);
+          fprintf(log_fd, "> Not adding state %d to list %d. char %d: %s pim: %s has_pim: %d found: %d\n",
+                  abs(state->id), l->id, state->c, code,
+                  pim == NULL ? "NULL" : "yes", l->has_pim, found);
 #endif
         return subs;
+        }
       }
 
       /* Do not add the state again when it exists with the same
@@ -4058,14 +4083,14 @@ skip_add:
 
   case NFA_SPLIT:
     /* order matters here */
-    subs = addstate(l, state->out, subs, pim, off);
-    subs = addstate(l, state->out1, subs, pim, off);
+    subs = addstate(l, state->out, subs, pim, off_arg);
+    subs = addstate(l, state->out1, subs, pim, off_arg);
     break;
 
   case NFA_EMPTY:
   case NFA_NOPEN:
   case NFA_NCLOSE:
-    subs = addstate(l, state->out, subs, pim, off);
+    subs = addstate(l, state->out, subs, pim, off_arg);
     break;
 
   case NFA_MOPEN:
@@ -4145,7 +4170,7 @@ skip_add:
       sub->list.line[subidx].start = reginput + off;
     }
 
-    subs = addstate(l, state->out, subs, pim, off);
+    subs = addstate(l, state->out, subs, pim, off_arg);
     /* "subs" may have changed, need to set "sub" again */
     if (state->c >= NFA_ZOPEN && state->c <= NFA_ZOPEN9)
       sub = &subs->synt;
@@ -4168,7 +4193,7 @@ skip_add:
                          ? subs->norm.list.multi[0].end_lnum >= 0
                          : subs->norm.list.line[0].end != NULL)) {
       /* Do not overwrite the position set by \ze. */
-      subs = addstate(l, state->out, subs, pim, off);
+      subs = addstate(l, state->out, subs, pim, off_arg);
       break;
     }
   case NFA_MCLOSE1:
@@ -4228,7 +4253,7 @@ skip_add:
       save_lpos.col = 0;
     }
 
-    subs = addstate(l, state->out, subs, pim, off);
+    subs = addstate(l, state->out, subs, pim, off_arg);
     /* "subs" may have changed, need to set "sub" again */
     if (state->c >= NFA_ZCLOSE && state->c <= NFA_ZCLOSE9)
       sub = &subs->synt;
@@ -4266,8 +4291,10 @@ addstate_here (
   int count;
   int listidx = *ip;
 
-  /* first add the state(s) at the end, so that we know how many there are */
-  addstate(l, state, subs, pim, 0);
+  /* First add the state(s) at the end, so that we know how many there are.
+   * Pass the listidx as offset (avoids adding another argument to
+   * addstate(). */
+  addstate(l, state, subs, pim, -listidx - ADDSTATE_HERE_OFFSET);
 
   /* when "*ip" was at the end of the list, nothing to do */
   if (listidx + 1 == tlen)
diff --git a/src/nvim/testdir/test_regexp_utf8.vim b/src/nvim/testdir/test_regexp_utf8.vim
index 9e9a3de500..7f3b31575d 100644
--- a/src/nvim/testdir/test_regexp_utf8.vim
+++ b/src/nvim/testdir/test_regexp_utf8.vim
@@ -97,3 +97,12 @@ func Test_recursive_substitute()
   call setwinvar(1, 'myvar', 1)
   bwipe!
 endfunc
+
+func Test_eow_with_optional()
+  let expected = ['abc def', 'abc', 'def', '', '', '', '', '', '', '']
+  for re in range(0, 2)
+    exe 'set re=' . re
+    let actual = matchlist('abc def', '\(abc\>\)\?\s*\(def\)')
+    call assert_equal(expected, actual)
+  endfor
+endfunc
diff --git a/src/nvim/version.c b/src/nvim/version.c
index d1d3e5a3c9..1b6e513c49 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -86,7 +86,7 @@ static int included_patches[] = {
   // 2358 NA
   // 2357,
   // 2356,
-  // 2355,
+  2355,
   // 2354,
   2353,
   // 2352 NA