vim-patch:9.1.1178: not possible to generate completion candidates using fuzzy matching

Problem:  not possible to generate completion candidates using fuzzy
          matching
Solution: add the 'completefuzzycollect' option for (some) ins-completion
          modes (glepnir)

fixes vim/vim#15296
fixes vim/vim#15295
fixes vim/vim#15294
closes: vim/vim#16032

https://github.com/vim/vim/commit/f31cfa29bf72b0cdf6fa1b60346ea4e187bcafd1

Co-authored-by: glepnir <glephunter@gmail.com>

14 files changed, 555 insertions, 187 deletions

diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index c0f3b31cf7..7bdacd73bf 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -131,7 +131,8 @@ LUA
 
 OPTIONS
 
-• todo
+• 'completefuzzycollect' enables fuzzy collection of candidates for (some)
+  |ins-completion| modes.
 
 PERFORMANCE
 
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index d477130a29..f44ea926b2 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1517,6 +1517,18 @@ A jump table for the options with a short description can be found at |Q_op|.
 	This option cannot be set from a |modeline| or in the |sandbox|, for
 	security reasons.
 
+					*'completefuzzycollect'* *'cfc'*
+'completefuzzycollect' 'cfc'	string	(default "")
+			global
+	This option enables fuzzy collection for (only some) specific
+	|ins-completion| modes, adjusting how items are gathered for fuzzy
+	matching based on input.
+	The option can contain the following values (separated by commas),
+	each enabling fuzzy collection for a specific completion mode:
+	files		file names
+	keyword		keyword completion in 'complete' and current file
+	whole_line	whole lines
+
 					*'completeitemalign'* *'cia'*
 'completeitemalign' 'cia'	string	(default "abbr,kind,menu")
 			global
@@ -1536,7 +1548,12 @@ A jump table for the options with a short description can be found at |Q_op|.
 	   fuzzy    Enable |fuzzy-matching| for completion candidates. This
 		    allows for more flexible and intuitive matching, where
 		    characters can be skipped and matches can be found even
-		    if the exact sequence is not typed.
+		    if the exact sequence is not typed. Note: This option
+		    does not affect the collection of candidate list, it only
+		    controls how completion candidates are reduced from the
+		    list of alternatives. If you want to use |fuzzy-matching|
+		    to gather more alternatives for your candidate list,
+		    see |'completefuzzycollect'|.
 
 	   longest  Only insert the longest common text of the matches.  If
 		    the menu is displayed you can use CTRL-L to add more
diff --git a/runtime/lua/vim/_meta/options.lua b/runtime/lua/vim/_meta/options.lua
index 58a8da4f26..cb199231c7 100644
--- a/runtime/lua/vim/_meta/options.lua
+++ b/runtime/lua/vim/_meta/options.lua
@@ -1044,6 +1044,21 @@ vim.o.cfu = vim.o.completefunc
 vim.bo.completefunc = vim.o.completefunc
 vim.bo.cfu = vim.bo.completefunc
 
+--- This option enables fuzzy collection for (only some) specific
+--- `ins-completion` modes, adjusting how items are gathered for fuzzy
+--- matching based on input.
+--- The option can contain the following values (separated by commas),
+--- each enabling fuzzy collection for a specific completion mode:
+--- files		file names
+--- keyword		keyword completion in 'complete' and current file
+--- whole_line	whole lines
+---
+--- @type string
+vim.o.completefuzzycollect = ""
+vim.o.cfc = vim.o.completefuzzycollect
+vim.go.completefuzzycollect = vim.o.completefuzzycollect
+vim.go.cfc = vim.go.completefuzzycollect
+
 --- A comma-separated list of strings that controls the alignment and
 --- display order of items in the popup menu during Insert mode
 --- completion.  The supported values are "abbr", "kind", and "menu".
@@ -1063,7 +1078,12 @@ vim.go.cia = vim.go.completeitemalign
 ---    fuzzy    Enable `fuzzy-matching` for completion candidates. This
 --- 	    allows for more flexible and intuitive matching, where
 --- 	    characters can be skipped and matches can be found even
---- 	    if the exact sequence is not typed.
+--- 	    if the exact sequence is not typed. Note: This option
+--- 	    does not affect the collection of candidate list, it only
+--- 	    controls how completion candidates are reduced from the
+--- 	    list of alternatives. If you want to use `fuzzy-matching`
+--- 	    to gather more alternatives for your candidate list,
+--- 	    see `'completefuzzycollect'`.
 ---
 ---    longest  Only insert the longest common text of the matches.  If
 --- 	    the menu is displayed you can use CTRL-L to add more
diff --git a/runtime/optwin.vim b/runtime/optwin.vim
index dff3ce39a4..bfeb3367a7 100644
--- a/runtime/optwin.vim
+++ b/runtime/optwin.vim
@@ -725,6 +725,8 @@ endif
 if has("insert_expand")
   call <SID>AddOption("complete", gettext("specifies how Insert mode completion works for CTRL-N and CTRL-P"))
   call append("$", "\t" .. s:local_to_buffer)
+  call <SID>OptionL("cfc")
+  call <SID>AddOption("completefuzzycollect", gettext("using fuzzy collect for defaule completion mode"))
   call <SID>OptionL("cpt")
   call <SID>AddOption("completeopt", gettext("whether to use a popup menu for Insert mode completion"))
   call <SID>OptionL("cot")
diff --git a/src/nvim/insexpand.c b/src/nvim/insexpand.c
index 226cfeb322..fc4c9c9807 100644
--- a/src/nvim/insexpand.c
+++ b/src/nvim/insexpand.c
@@ -215,6 +215,13 @@ static compl_T *compl_curr_match = NULL;
 static compl_T *compl_shown_match = NULL;
 static compl_T *compl_old_match = NULL;
 
+/// list used to store the compl_T which have the max score
+/// used for completefuzzycollect
+static compl_T **compl_best_matches = NULL;
+static int compl_num_bests = 0;
+/// inserted a longest when completefuzzycollect enabled
+static bool compl_cfc_longest_ins = false;
+
 /// After using a cursor key <Enter> selects a match in the popup menu,
 /// otherwise it inserts a line break.
 static bool compl_enter_selects = false;
@@ -732,7 +739,7 @@ static char *ins_compl_infercase_gettext(const char *str, int char_len, int comp
 ///
 /// @param[in]  cont_s_ipos  next ^X<> will set initial_pos
 int ins_compl_add_infercase(char *str_arg, int len, bool icase, char *fname, Direction dir,
-                            bool cont_s_ipos)
+                            bool cont_s_ipos, int score)
   FUNC_ATTR_NONNULL_ARG(1)
 {
   char *str = str_arg;
@@ -777,11 +784,26 @@ int ins_compl_add_infercase(char *str_arg, int len, bool icase, char *fname, Dir
     flags |= CP_ICASE;
   }
 
-  int res = ins_compl_add(str, len, fname, NULL, false, NULL, dir, flags, false, NULL);
+  int res = ins_compl_add(str, len, fname, NULL, false, NULL, dir, flags, false, NULL, score);
   xfree(tofree);
   return res;
 }
 
+/// Check if ctrl_x_mode has been configured in 'completefuzzycollect'
+static bool cfc_has_mode(void)
+{
+  switch (ctrl_x_mode) {
+  case CTRL_X_NORMAL:
+    return (cfc_flags & kOptCfcFlagKeyword) != 0;
+  case CTRL_X_FILES:
+    return (cfc_flags & kOptCfcFlagFiles) != 0;
+  case CTRL_X_WHOLE_LINE:
+    return (cfc_flags & kOptCfcFlagWholeLine) != 0;
+  default:
+    return false;
+  }
+}
+
 /// free cptext
 static inline void free_cptext(char *const *const cptext)
 {
@@ -818,12 +840,13 @@ static inline void free_cptext(char *const *const cptext)
 ///         returned in case of error.
 static int ins_compl_add(char *const str, int len, char *const fname, char *const *const cptext,
                          const bool cptext_allocated, typval_T *user_data, const Direction cdir,
-                         int flags_arg, const bool adup, const int *user_hl)
+                         int flags_arg, const bool adup, const int *user_hl, const int score)
   FUNC_ATTR_NONNULL_ARG(1)
 {
   compl_T *match;
   const Direction dir = (cdir == kDirectionNotSet ? compl_direction : cdir);
   int flags = flags_arg;
+  bool inserted = false;
 
   if (flags & CP_FAST) {
     fast_breakcheck();
@@ -864,6 +887,7 @@ static int ins_compl_add(char *const str, int len, char *const fname, char *cons
   match = xcalloc(1, sizeof(compl_T));
   match->cp_number = flags & CP_ORIGINAL_TEXT ? 0 : -1;
   match->cp_str = cbuf_to_string(str, (size_t)len);
+  match->cp_score = score;
 
   // match-fname is:
   // - compl_curr_match->cp_fname if it is a string equal to fname.
@@ -907,6 +931,33 @@ static int ins_compl_add(char *const str, int len, char *const fname, char *cons
   // current match in the list of matches .
   if (compl_first_match == NULL) {
     match->cp_next = match->cp_prev = NULL;
+  } else if (cfc_has_mode() && score > 0 && compl_get_longest) {
+    compl_T *current = compl_first_match->cp_next;
+    compl_T *prev = compl_first_match;
+    inserted = false;
+    // The direction is ignored when using longest and
+    // completefuzzycollect, because matches are inserted
+    // and sorted by score.
+    while (current != NULL && current != compl_first_match) {
+      if (current->cp_score < score) {
+        match->cp_next = current;
+        match->cp_prev = current->cp_prev;
+        if (current->cp_prev) {
+          current->cp_prev->cp_next = match;
+        }
+        current->cp_prev = match;
+        inserted = true;
+        break;
+      }
+      prev = current;
+      current = current->cp_next;
+    }
+    if (!inserted) {
+      prev->cp_next = match;
+      match->cp_prev = prev;
+      match->cp_next = compl_first_match;
+      compl_first_match->cp_prev = match;
+    }
   } else if (dir == FORWARD) {
     match->cp_next = compl_curr_match->cp_next;
     match->cp_prev = compl_curr_match;
@@ -925,7 +976,7 @@ static int ins_compl_add(char *const str, int len, char *const fname, char *cons
   compl_curr_match = match;
 
   // Find the longest common string if still doing that.
-  if (compl_get_longest && (flags & CP_ORIGINAL_TEXT) == 0) {
+  if (compl_get_longest && (flags & CP_ORIGINAL_TEXT) == 0 && !cfc_has_mode()) {
     ins_compl_longest_match(match);
   }
 
@@ -1013,9 +1064,7 @@ static void ins_compl_longest_match(compl_T *match)
     compl_leader = copy_string(match->cp_str, NULL);
 
     bool had_match = (curwin->w_cursor.col > compl_col);
-    ins_compl_delete(false);
-    ins_compl_insert_bytes(compl_leader.data + get_compl_len(), -1);
-    ins_redraw(false);
+    ins_compl_longest_insert(compl_leader.data);
 
     // When the match isn't there (to avoid matching itself) remove it
     // again after redrawing.
@@ -1049,9 +1098,7 @@ static void ins_compl_longest_match(compl_T *match)
     compl_leader.size = (size_t)(p - compl_leader.data);
 
     bool had_match = (curwin->w_cursor.col > compl_col);
-    ins_compl_delete(false);
-    ins_compl_insert_bytes(compl_leader.data + get_compl_len(), -1);
-    ins_redraw(false);
+    ins_compl_longest_insert(compl_leader.data);
 
     // When the match isn't there (to avoid matching itself) remove it
     // again after redrawing.
@@ -1072,7 +1119,7 @@ static void ins_compl_add_matches(int num_matches, char **matches, int icase)
 
   for (int i = 0; i < num_matches && add_r != FAIL; i++) {
     add_r = ins_compl_add(matches[i], -1, NULL, NULL, false, NULL, dir,
-                          CP_FAST | (icase ? CP_ICASE : 0), false, NULL);
+                          CP_FAST | (icase ? CP_ICASE : 0), false, NULL, 0);
     if (add_r == OK) {
       // If dir was BACKWARD then honor it just once.
       dir = FORWARD;
@@ -1238,6 +1285,7 @@ static int ins_compl_build_pum(void)
   bool compl_no_select = (cur_cot_flags & kOptCotFlagNoselect) != 0;
   bool fuzzy_filter = (cur_cot_flags & kOptCotFlagFuzzy) != 0;
   bool fuzzy_sort = fuzzy_filter && !(cur_cot_flags & kOptCotFlagNosort);
+
   compl_T *match_head = NULL, *match_tail = NULL;
 
   // If the current match is the original text don't find the first
@@ -1554,7 +1602,7 @@ static void ins_compl_dictionaries(char *dict_start, char *pat, int flags, bool
       spell_dump_compl(ptr, regmatch.rm_ic, &dir, 0);
     } else if (count > 0) {  // avoid warning for using "files" uninit
       ins_compl_files(count, files, thesaurus, flags,
-                      &regmatch, buf, &dir);
+                      (cfc_has_mode() ? NULL : &regmatch), buf, &dir);
       if (flags != DICT_EXACT) {
         FreeWild(count, files);
       }
@@ -1605,7 +1653,7 @@ static int thesaurus_add_words_in_line(char *fname, char **buf_arg, int dir, con
     // Add the word. Skip the regexp match.
     if (wstart != skip_word) {
       status = ins_compl_add_infercase(wstart, (int)(ptr - wstart), p_ic,
-                                       fname, dir, false);
+                                       fname, dir, false, 0);
       if (status == FAIL) {
         break;
       }
@@ -1622,6 +1670,11 @@ static void ins_compl_files(int count, char **files, bool thesaurus, int flags,
                             regmatch_T *regmatch, char *buf, Direction *dir)
   FUNC_ATTR_NONNULL_ARG(2, 7)
 {
+  bool in_fuzzy_collect = cfc_has_mode() && ctrl_x_mode_normal();
+
+  char *leader = in_fuzzy_collect ? ins_compl_leader() : NULL;
+  int leader_len = in_fuzzy_collect ? (int)ins_compl_leader_len() : 0;
+
   for (int i = 0; i < count && !got_int && !compl_interrupted; i++) {
     FILE *fp = os_fopen(files[i], "r");  // open dictionary file
     if (flags != DICT_EXACT && !shortmess(SHM_COMPLETIONSCAN)) {
@@ -1640,27 +1693,51 @@ static void ins_compl_files(int count, char **files, bool thesaurus, int flags,
     // Check each line for a match.
     while (!got_int && !compl_interrupted && !vim_fgets(buf, LSIZE, fp)) {
       char *ptr = buf;
-      while (vim_regexec(regmatch, buf, (colnr_T)(ptr - buf))) {
-        ptr = regmatch->startp[0];
-        ptr = ctrl_x_mode_line_or_eval() ? find_line_end(ptr) : find_word_end(ptr);
-        int add_r = ins_compl_add_infercase(regmatch->startp[0],
-                                            (int)(ptr - regmatch->startp[0]),
-                                            p_ic, files[i], *dir, false);
-        if (thesaurus) {
-          // For a thesaurus, add all the words in the line
-          ptr = buf;
-          add_r = thesaurus_add_words_in_line(files[i], &ptr, *dir, regmatch->startp[0]);
-        }
-        if (add_r == OK) {
-          // if dir was BACKWARD then honor it just once
-          *dir = FORWARD;
-        } else if (add_r == FAIL) {
-          break;
+      if (regmatch != NULL) {
+        while (vim_regexec(regmatch, buf, (colnr_T)(ptr - buf))) {
+          ptr = regmatch->startp[0];
+          ptr = ctrl_x_mode_line_or_eval() ? find_line_end(ptr) : find_word_end(ptr);
+          int add_r = ins_compl_add_infercase(regmatch->startp[0],
+                                              (int)(ptr - regmatch->startp[0]),
+                                              p_ic, files[i], *dir, false, 0);
+          if (thesaurus) {
+            // For a thesaurus, add all the words in the line
+            ptr = buf;
+            add_r = thesaurus_add_words_in_line(files[i], &ptr, *dir, regmatch->startp[0]);
+          }
+          if (add_r == OK) {
+            // if dir was BACKWARD then honor it just once
+            *dir = FORWARD;
+          } else if (add_r == FAIL) {
+            break;
+          }
+          // avoid expensive call to vim_regexec() when at end
+          // of line
+          if (*ptr == '\n' || got_int) {
+            break;
+          }
         }
-        // avoid expensive call to vim_regexec() when at end
-        // of line
-        if (*ptr == '\n' || got_int) {
-          break;
+      } else if (in_fuzzy_collect && leader_len > 0) {
+        char *line_end = find_line_end(ptr);
+        while (ptr < line_end) {
+          int score = 0;
+          int len = 0;
+          if (fuzzy_match_str_in_line(&ptr, leader, &len, NULL, &score)) {
+            char *end_ptr = ctrl_x_mode_line_or_eval() ? find_line_end(ptr) : find_word_end(ptr);
+            int add_r = ins_compl_add_infercase(ptr, (int)(end_ptr - ptr),
+                                                p_ic, files[i], *dir, false, score);
+            if (add_r == FAIL) {
+              break;
+            }
+            ptr = end_ptr;  // start from next word
+            if (compl_get_longest && ctrl_x_mode_normal()
+                && compl_first_match->cp_next
+                && score == compl_first_match->cp_next->cp_score) {
+              compl_num_bests++;
+            }
+          } else if (find_word_end(ptr) == line_end) {
+            break;
+          }
         }
       }
       line_breakcheck();
@@ -1746,6 +1823,7 @@ void ins_compl_clear(void)
 {
   compl_cont_status = 0;
   compl_started = false;
+  compl_cfc_longest_ins = false;
   compl_matches = 0;
   compl_selected_item = -1;
   compl_ins_end_col = 0;
@@ -2744,7 +2822,7 @@ static int ins_compl_add_tv(typval_T *const tv, const Direction dir, bool fast)
     return FAIL;
   }
   int status = ins_compl_add((char *)word, -1, NULL, cptext, true,
-                             &user_data, dir, flags, dup, user_hl);
+                             &user_data, dir, flags, dup, user_hl, 0);
   if (status != OK) {
     tv_clear(&user_data);
   }
@@ -2840,7 +2918,7 @@ static void set_completion(colnr_T startcol, list_T *list)
   }
   if (ins_compl_add(compl_orig_text.data, (int)compl_orig_text.size,
                     NULL, NULL, false, NULL, 0,
-                    flags | CP_FAST, false, NULL) != OK) {
+                    flags | CP_FAST, false, NULL, 0) != OK) {
     return;
   }
 
@@ -3310,6 +3388,87 @@ static int compare_scores(const void *a, const void *b)
                             : (score_a > score_b ? -1 : 1);
 }
 
+/// insert prefix with redraw
+static void ins_compl_longest_insert(char *prefix)
+{
+  ins_compl_delete(false);
+  ins_compl_insert_bytes(prefix + get_compl_len(), -1);
+  ins_redraw(false);
+}
+
+/// Calculate the longest common prefix among the best fuzzy matches
+/// stored in compl_best_matches, and insert it as the longest.
+static void fuzzy_longest_match(void)
+{
+  if (compl_num_bests == 0) {
+    return;
+  }
+
+  compl_T *nn_compl = compl_first_match->cp_next->cp_next;
+  bool more_candidates = nn_compl && nn_compl != compl_first_match;
+
+  compl_T *compl = ctrl_x_mode_whole_line() ? compl_first_match
+                                            : compl_first_match->cp_next;
+  if (compl_num_bests == 1) {
+    // no more candidates insert the match str
+    if (!more_candidates) {
+      ins_compl_longest_insert(compl->cp_str.data);
+      compl_num_bests = 0;
+    }
+    compl_num_bests = 0;
+    return;
+  }
+
+  compl_best_matches = (compl_T **)xmalloc((size_t)compl_num_bests * sizeof(compl_T *));
+
+  for (int i = 0; compl != NULL && i < compl_num_bests; i++) {
+    compl_best_matches[i] = compl;
+    compl = compl->cp_next;
+  }
+
+  char *prefix = compl_best_matches[0]->cp_str.data;
+  int prefix_len = (int)strlen(prefix);
+
+  for (int i = 1; i < compl_num_bests; i++) {
+    char *match_str = compl_best_matches[i]->cp_str.data;
+    char *prefix_ptr = prefix;
+    char *match_ptr = match_str;
+    int j = 0;
+
+    while (j < prefix_len && *match_ptr != NUL && *prefix_ptr != NUL) {
+      if (strncmp(prefix_ptr, match_ptr, (size_t)utfc_ptr2len(prefix_ptr)) != 0) {
+        break;
+      }
+
+      MB_PTR_ADV(prefix_ptr);
+      MB_PTR_ADV(match_ptr);
+      j++;
+    }
+
+    if (j > 0) {
+      prefix_len = j;
+    }
+  }
+
+  char *leader = ins_compl_leader();
+  size_t leader_len = leader != NULL ? strlen(leader) : 0;
+
+  // skip non-consecutive prefixes
+  if (strncmp(prefix, leader, leader_len) != 0) {
+    goto end;
+  }
+
+  prefix = xmemdupz(compl_best_matches[0]->cp_str.data, (size_t)prefix_len);
+  ins_compl_longest_insert(prefix);
+  compl_cfc_longest_ins = true;
+  xfree(prefix);
+
+end:
+  xfree(compl_best_matches);
+  compl_best_matches = NULL;
+  compl_num_bests = 0;
+}
+
 /// Get the next set of filename matching "compl_pattern".
 static void get_next_filename_completion(void)
 {
@@ -3317,7 +3476,10 @@ static void get_next_filename_completion(void)
   int num_matches;
   char *leader = ins_compl_leader();
   size_t leader_len = ins_compl_leader_len();
-  bool in_fuzzy = ((get_cot_flags() & kOptCotFlagFuzzy) != 0 && leader_len > 0);
+  bool in_fuzzy_collect = (cfc_has_mode() && leader_len > 0);
+  bool need_collect_bests = in_fuzzy_collect && compl_get_longest;
+  int max_score = 0;
+  Direction dir = compl_direction;
 
 #ifdef BACKSLASH_IN_FILENAME
   char pathsep = (curbuf->b_p_csl[0] == 's')
@@ -3326,7 +3488,7 @@ static void get_next_filename_completion(void)
   char pathsep = PATHSEP;
 #endif
 
-  if (in_fuzzy) {
+  if (in_fuzzy_collect) {
 #ifdef BACKSLASH_IN_FILENAME
     if (curbuf->b_p_csl[0] == 's') {
       for (size_t i = 0; i < leader_len; i++) {
@@ -3349,7 +3511,7 @@ static void get_next_filename_completion(void)
       API_CLEAR_STRING(compl_pattern);
       compl_pattern = cbuf_to_string("*", 1);
     } else if (*(last_sep + 1) == NUL) {
-      in_fuzzy = false;
+      in_fuzzy_collect = false;
     } else {
       // Split leader into path and file parts
       size_t path_len = (size_t)(last_sep - leader) + 1;
@@ -3389,7 +3551,7 @@ static void get_next_filename_completion(void)
   }
 #endif
 
-  if (in_fuzzy) {
+  if (in_fuzzy_collect) {
     garray_T fuzzy_indices;
     ga_init(&fuzzy_indices, sizeof(int), 10);
     compl_fuzzy_scores = (int *)xmalloc(sizeof(int) * (size_t)num_matches);
@@ -3408,14 +3570,24 @@ static void get_next_filename_completion(void)
       int *fuzzy_indices_data = (int *)fuzzy_indices.ga_data;
       qsort(fuzzy_indices_data, (size_t)fuzzy_indices.ga_len, sizeof(int), compare_scores);
 
-      char **sorted_matches = (char **)xmalloc(sizeof(char *) * (size_t)fuzzy_indices.ga_len);
       for (int i = 0; i < fuzzy_indices.ga_len; i++) {
-        sorted_matches[i] = xstrdup(matches[fuzzy_indices_data[i]]);
+        char *match = matches[fuzzy_indices_data[i]];
+        int current_score = compl_fuzzy_scores[fuzzy_indices_data[i]];
+        if (ins_compl_add(match, -1, NULL, NULL, false, NULL, dir,
+                          CP_FAST | ((p_fic || p_wic) ? CP_ICASE : 0),
+                          false, NULL, current_score) == OK) {
+          dir = FORWARD;
+        }
+
+        if (need_collect_bests) {
+          if (i == 0 || current_score == max_score) {
+            compl_num_bests++;
+            max_score = current_score;
+          }
+        }
       }
 
       FreeWild(num_matches, matches);
-      matches = sorted_matches;
-      num_matches = fuzzy_indices.ga_len;
     } else if (leader_len > 0) {
       FreeWild(num_matches, matches);
       num_matches = 0;
@@ -3423,6 +3595,11 @@ static void get_next_filename_completion(void)
 
     xfree(compl_fuzzy_scores);
     ga_clear(&fuzzy_indices);
+
+    if (compl_num_bests > 0 && compl_get_longest) {
+      fuzzy_longest_match();
+    }
+    return;
   }
 
   if (num_matches > 0) {
@@ -3552,8 +3729,9 @@ static int get_next_default_completion(ins_compl_next_state_T *st, pos_T *start_
 {
   char *ptr = NULL;
   int len = 0;
-  bool in_fuzzy = (get_cot_flags() & kOptCotFlagFuzzy) != 0 && compl_length > 0;
+  bool in_collect = (cfc_has_mode() && compl_length > 0);
   char *leader = ins_compl_leader();
+  int score = 0;
 
   // If 'infercase' is set, don't use 'smartcase' here
   const int save_p_scs = p_scs;
@@ -3569,7 +3747,7 @@ static int get_next_default_completion(ins_compl_next_state_T *st, pos_T *start_
   const int save_p_ws = p_ws;
   if (st->ins_buf != curbuf) {
     p_ws = false;
-  } else if (*st->e_cpt == '.' && !in_fuzzy) {
+  } else if (*st->e_cpt == '.') {
     p_ws = true;
   }
   bool looped_around = false;
@@ -3578,16 +3756,17 @@ static int get_next_default_completion(ins_compl_next_state_T *st, pos_T *start_
     bool cont_s_ipos = false;
 
     msg_silent++;  // Don't want messages for wrapscan.
-    // ctrl_x_mode_line_or_eval() || word-wise search that
-    // has added a word that was at the beginning of the line.
-    if ((ctrl_x_mode_whole_line() && !in_fuzzy) || ctrl_x_mode_eval()
-        || (compl_cont_status & CONT_SOL)) {
-      found_new_match = search_for_exact_line(st->ins_buf, st->cur_match_pos,
-                                              compl_direction, compl_pattern.data);
-    } else if (in_fuzzy) {
+
+    if (in_collect) {
       found_new_match = search_for_fuzzy_match(st->ins_buf,
                                                st->cur_match_pos, leader, compl_direction,
-                                               start_pos, &len, &ptr, ctrl_x_mode_whole_line());
+                                               start_pos, &len, &ptr, &score);
+      // ctrl_x_mode_line_or_eval() || word-wise search that
+      // has added a word that was at the beginning of the line.
+    } else if (ctrl_x_mode_whole_line() || ctrl_x_mode_eval()
+               || (compl_cont_status & CONT_SOL)) {
+      found_new_match = search_for_exact_line(st->ins_buf, st->cur_match_pos,
+                                              compl_direction, compl_pattern.data);
     } else {
       found_new_match = searchit(NULL, st->ins_buf, st->cur_match_pos,
                                  NULL, compl_direction, compl_pattern.data,
@@ -3635,7 +3814,7 @@ static int get_next_default_completion(ins_compl_next_state_T *st, pos_T *start_
       continue;
     }
 
-    if (!in_fuzzy) {
+    if (!in_collect) {
       ptr = ins_compl_get_next_word_or_line(st->ins_buf, st->cur_match_pos,
                                             &len, &cont_s_ipos);
     }
@@ -3646,7 +3825,10 @@ static int get_next_default_completion(ins_compl_next_state_T *st, pos_T *start_
 
     if (ins_compl_add_infercase(ptr, len, p_ic,
                                 st->ins_buf == curbuf ? NULL : st->ins_buf->b_sfname,
-                                0, cont_s_ipos) != NOTDONE) {
+                                0, cont_s_ipos, score) != NOTDONE) {
+      if (in_collect && score == compl_first_match->cp_next->cp_score) {
+        compl_num_bests++;
+      }
       found_new_match = OK;
       break;
     }
@@ -3725,7 +3907,7 @@ static void get_next_bufname_token(void)
       char *tail = path_tail(b->b_sfname);
       if (strncmp(tail, compl_orig_text.data, compl_orig_text.size) == 0) {
         ins_compl_add(tail, (int)strlen(tail), NULL, NULL, false, NULL, 0,
-                      p_ic ? CP_ICASE : 0, false, NULL);
+                      p_ic ? CP_ICASE : 0, false, NULL, 0);
       }
     }
   }
@@ -3839,6 +4021,10 @@ static int ins_compl_get_exp(pos_T *ini)
     i = ins_compl_make_cyclic();
   }
 
+  if (cfc_has_mode() && compl_get_longest && compl_num_bests > 0) {
+    fuzzy_longest_match();
+  }
+
   if (compl_old_match != NULL) {
     // If several matches were added (FORWARD) or the search failed and has
     // just been made cyclic then we have to move compl_curr_match to the
@@ -4865,9 +5051,9 @@ static int ins_compl_start(void)
   if (p_ic) {
     flags |= CP_ICASE;
   }
-  if (ins_compl_add(compl_orig_text.data, (int)compl_orig_text.size,
+  if (ins_compl_add(compl_orig_text.data, -1,
                     NULL, NULL, false, NULL, 0,
-                    flags, false, NULL) != OK) {
+                    flags, false, NULL, 0) != OK) {
     API_CLEAR_STRING(compl_pattern);
     API_CLEAR_STRING(compl_orig_text);
     kv_destroy(compl_orig_extmarks);
diff --git a/src/nvim/option_vars.h b/src/nvim/option_vars.h
index 3f0445675d..2e5698870f 100644
--- a/src/nvim/option_vars.h
+++ b/src/nvim/option_vars.h
@@ -294,8 +294,10 @@ EXTERN char *p_cms;             ///< 'commentstring'
 EXTERN char *p_cpt;             ///< 'complete'
 EXTERN OptInt p_columns;        ///< 'columns'
 EXTERN int p_confirm;           ///< 'confirm'
+EXTERN char *p_cfc;             ///< 'completefuzzycollect'
+EXTERN unsigned cfc_flags;      ///< flags from 'completefuzzycollect'
 EXTERN char *p_cia;             ///< 'completeitemalign'
-EXTERN unsigned cia_flags;      ///<  order flags of 'completeitemalign'
+EXTERN unsigned cia_flags;      ///< order flags of 'completeitemalign'
 EXTERN char *p_cot;             ///< 'completeopt'
 EXTERN unsigned cot_flags;      ///< flags from 'completeopt'
 #ifdef BACKSLASH_IN_FILENAME
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index c028999d61..8ee9434a60 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -1460,6 +1460,30 @@ local options = {
       varname = 'p_cfu',
     },
     {
+      abbreviation = 'cfc',
+      defaults = '',
+      values = { 'keyword', 'files', 'whole_line' },
+      flags = true,
+      deny_duplicates = true,
+      desc = [=[
+        This option enables fuzzy collection for (only some) specific
+        |ins-completion| modes, adjusting how items are gathered for fuzzy
+        matching based on input.
+        The option can contain the following values (separated by commas),
+        each enabling fuzzy collection for a specific completion mode:
+        files		file names
+        keyword		keyword completion in 'complete' and current file
+        whole_line	whole lines
+      ]=],
+      full_name = 'completefuzzycollect',
+      list = 'onecomma',
+      scope = { 'global' },
+      short_desc = N_('use fuzzy collection for specific completion modes'),
+      type = 'string',
+      varname = 'p_cfc',
+      flags_varname = 'cfc_flags',
+    },
+    {
       abbreviation = 'cia',
       cb = 'did_set_completeitemalign',
       defaults = 'abbr,kind,menu',
@@ -1505,7 +1529,12 @@ local options = {
            fuzzy    Enable |fuzzy-matching| for completion candidates. This
         	    allows for more flexible and intuitive matching, where
         	    characters can be skipped and matches can be found even
-        	    if the exact sequence is not typed.
+        	    if the exact sequence is not typed. Note: This option
+        	    does not affect the collection of candidate list, it only
+        	    controls how completion candidates are reduced from the
+        	    list of alternatives. If you want to use |fuzzy-matching|
+        	    to gather more alternatives for your candidate list,
+        	    see |'completefuzzycollect'|.
 
            longest  Only insert the longest common text of the matches.  If
         	    the menu is displayed you can use CTRL-L to add more
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index 3a6b4c9936..c6cc7af8cd 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -84,6 +84,7 @@ void didset_string_options(void)
   check_str_opt(kOptCasemap, NULL);
   check_str_opt(kOptBackupcopy, NULL);
   check_str_opt(kOptBelloff, NULL);
+  check_str_opt(kOptCompletefuzzycollect, NULL);
   check_str_opt(kOptCompleteopt, NULL);
   check_str_opt(kOptSessionoptions, NULL);
   check_str_opt(kOptViewoptions, NULL);
diff --git a/src/nvim/search.c b/src/nvim/search.c
index 07bc84ba84..b31263e127 100644
--- a/src/nvim/search.c
+++ b/src/nvim/search.c
@@ -3620,11 +3620,18 @@ garray_T *fuzzy_match_str_with_pos(char *const str, const char *const pat)
   return match_positions;
 }
 
-/// This function searches for a fuzzy match of the pattern `pat` within the
-/// line pointed to by `*ptr`. It splits the line into words, performs fuzzy
-/// matching on each word, and returns the length and position of the first
-/// matched word.
-static bool fuzzy_match_str_in_line(char **ptr, char *pat, int *len, pos_T *current_pos)
+/// This function splits the line pointed to by `*ptr` into words and performs
+/// a fuzzy match for the pattern `pat` on each word. It iterates through the
+/// line, moving `*ptr` to the start of each word during the process.
+///
+/// If a match is found:
+/// - `*ptr` points to the start of the matched word.
+/// - `*len` is set to the length of the matched word.
+/// - `*score` contains the match score.
+///
+/// If no match is found, `*ptr` is updated to point beyond the last word
+/// or to the end of the line.
+bool fuzzy_match_str_in_line(char **ptr, char *pat, int *len, pos_T *current_pos, int *score)
 {
   char *str = *ptr;
   char *strBegin = str;
@@ -3649,14 +3656,16 @@ static bool fuzzy_match_str_in_line(char **ptr, char *pat, int *len, pos_T *curr
     *end = NUL;
 
     // Perform fuzzy match
-    int result = fuzzy_match_str(start, pat);
+    *score = fuzzy_match_str(start, pat);
     *end = save_end;
 
-    if (result > 0) {
+    if (*score > 0) {
       *len = (int)(end - start);
-      current_pos->col += (int)(end - strBegin);
       found = true;
       *ptr = start;
+      if (current_pos) {
+        current_pos->col += (int)(end - strBegin);
+      }
       break;
     }
 
@@ -3678,13 +3687,14 @@ static bool fuzzy_match_str_in_line(char **ptr, char *pat, int *len, pos_T *curr
 ///
 /// Return true if a match is found, otherwise false.
 bool search_for_fuzzy_match(buf_T *buf, pos_T *pos, char *pattern, int dir, pos_T *start_pos,
-                            int *len, char **ptr, bool whole_line)
+                            int *len, char **ptr, int *score)
 {
   pos_T current_pos = *pos;
   pos_T circly_end;
   bool found_new_match = false;
   bool looped_around = false;
 
+  bool whole_line = ctrl_x_mode_whole_line();
   if (whole_line) {
     current_pos.lnum += dir;
   }
@@ -3709,11 +3719,13 @@ bool search_for_fuzzy_match(buf_T *buf, pos_T *pos, char *pattern, int dir, pos_
       *ptr = ml_get_buf(buf, current_pos.lnum);
       // If ptr is end of line is reached, move to next line
       // or previous line based on direction
-      if (**ptr != NUL) {
+      if (*ptr != NULL && **ptr != NUL) {
         if (!whole_line) {
           *ptr += current_pos.col;
-          // Try to find a fuzzy match in the current line starting from current position
-          found_new_match = fuzzy_match_str_in_line(ptr, pattern, len, &current_pos);
+          // Try to find a fuzzy match in the current line starting
+          // from current position
+          found_new_match = fuzzy_match_str_in_line(ptr, pattern,
+                                                    len, &current_pos, score);
           if (found_new_match) {
             if (ctrl_x_mode_normal()) {
               if (strncmp(*ptr, pattern, (size_t)(*len)) == 0 && pattern[*len] == NUL) {
@@ -4227,7 +4239,7 @@ search_line:
         const int add_r = ins_compl_add_infercase(aux, i, p_ic,
                                                   curr_fname == curbuf->b_fname
                                                   ? NULL : curr_fname,
-                                                  dir, cont_s_ipos);
+                                                  dir, cont_s_ipos, 0);
         if (add_r == OK) {
           // if dir was BACKWARD then honor it just once
           dir = FORWARD;
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index 7437a7a32f..c8c3622347 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -3483,7 +3483,7 @@ static void dump_word(slang_T *slang, char *word, char *pat, Direction *dir, int
               ? mb_strnicmp(p, pat, strlen(pat)) == 0
               : strncmp(p, pat, strlen(pat)) == 0)
              && ins_compl_add_infercase(p, (int)strlen(p),
-                                        p_ic, NULL, *dir, false) == OK) {
+                                        p_ic, NULL, *dir, false, 0) == OK) {
     // if dir was BACKWARD then honor it just once
     *dir = FORWARD;
   }
diff --git a/test/functional/ui/popupmenu_spec.lua b/test/functional/ui/popupmenu_spec.lua
index 76673c84b8..9403f39ba1 100644
--- a/test/functional/ui/popupmenu_spec.lua
+++ b/test/functional/ui/popupmenu_spec.lua
@@ -6932,25 +6932,48 @@ describe('builtin popupmenu', function()
         ]])
         feed('o<BS><C-R>=Comp()<CR>')
         screen:expect_unchanged(true)
+        feed('<C-E><Esc>')
+
+        command('hi PmenuMatchSel guibg=NONE')
+        command('hi PmenuMatch guibg=NONE')
+        command('set cot=menu,noinsert,fuzzy')
+        feed('S<C-X><C-O>')
+        screen:expect(pum_start)
+        feed('fb')
+        screen:expect([[
+          fb^                              |
+          {ms:f}{s:oo}{ms:B}{s:az  fookind }{1:                }|
+          {mn:f}{n:oo}{mn:b}{n:ar  fookind }{1:                }|
+          {mn:f}{n:oo}{mn:b}{n:ala fookind }{1:                }|
+          {1:~                               }|*15
+          {2:-- }{5:match 1 of 9}                 |
+        ]])
+
+        feed('<C-E><Esc>')
+      end)
+
+      it('completefuzzycollect', function()
+        exec([[
+          set completefuzzycollect=keyword,files
+          set completeopt=menu,menuone
+        ]])
 
-        feed('<Esc>')
-        command('set completeopt+=fuzzy,menu')
         feed('S hello helio hero h<C-X><C-P>')
         screen:expect([[
-           hello helio hero h^             |
-          {1:~                }{n: }{mn:h}{n:ero         }{1: }|
-          {1:~                }{n: }{mn:h}{n:elio        }{1: }|
-          {1:~                }{s: }{ms:h}{s:ello        }{1: }|
+           hello helio hero hello^         |
+          {1:~                }{n: hero         }{1: }|
+          {1:~                }{n: helio        }{1: }|
+          {1:~                }{s: hello        }{1: }|
           {1:~                               }|*15
           {2:-- }{5:match 1 of 3}                 |
         ]])
 
         feed('<Esc>S hello helio hero h<C-X><C-P><C-P>')
         screen:expect([[
-           hello helio hero h^             |
-          {1:~                }{n: }{mn:h}{n:ero         }{1: }|
-          {1:~                }{s: }{ms:h}{s:elio        }{1: }|
-          {1:~                }{n: }{mn:h}{n:ello        }{1: }|
+           hello helio hero helio^         |
+          {1:~                }{n: hero         }{1: }|
+          {1:~                }{s: helio        }{1: }|
+          {1:~                }{n: hello        }{1: }|
           {1:~                               }|*15
           {2:-- }{5:match 2 of 3}                 |
         ]])
@@ -6962,23 +6985,6 @@ describe('builtin popupmenu', function()
           {2:-- }{6:Pattern not found}            |
         ]])
         feed('<C-E><Esc>')
-
-        command('hi PmenuMatchSel guibg=NONE')
-        command('hi PmenuMatch guibg=NONE')
-        command('set cot=menu,noinsert,fuzzy')
-        feed('S<C-X><C-O>')
-        screen:expect(pum_start)
-        feed('fb')
-        screen:expect([[
-          fb^                              |
-          {ms:f}{s:oo}{ms:B}{s:az  fookind }{1:                }|
-          {mn:f}{n:oo}{mn:b}{n:ar  fookind }{1:                }|
-          {mn:f}{n:oo}{mn:b}{n:ala fookind }{1:                }|
-          {1:~                               }|*15
-          {2:-- }{5:match 1 of 9}                 |
-        ]])
-
-        feed('<C-E><Esc>')
       end)
 
       -- oldtest: Test_pum_highlights_match_with_abbr()
diff --git a/test/old/testdir/gen_opt_test.vim b/test/old/testdir/gen_opt_test.vim
index aa4c5ec6e0..2127945624 100644
--- a/test/old/testdir/gen_opt_test.vim
+++ b/test/old/testdir/gen_opt_test.vim
@@ -189,6 +189,9 @@ let test_values = {
       "\ 'completeopt': [['', 'menu', 'menuone', 'longest', 'preview', 'popup',
       "\ "		'popuphidden', 'noinsert', 'noselect', 'fuzzy', 'preinsert', 'menu,longest'],
       "\ "		['xxx', 'menu,,,longest,']],
+      \ 'completefuzzycollect': [['', 'keyword', 'files', 'whole_line',
+      \		'keyword,whole_line', 'files,whole_line', 'keyword,files,whole_line'],
+      \		['xxx', 'keyword,,,whole_line,']],
       \ 'completeitemalign': [['abbr,kind,menu', 'menu,abbr,kind'],
       \		['', 'xxx', 'abbr', 'abbr,menu', 'abbr,menu,kind,abbr',
       \		'abbr1234,kind,menu']],
diff --git a/test/old/testdir/test_ins_complete.vim b/test/old/testdir/test_ins_complete.vim
index 97a02adf0d..cd2f5d9307 100644
--- a/test/old/testdir/test_ins_complete.vim
+++ b/test/old/testdir/test_ins_complete.vim
@@ -2763,7 +2763,7 @@ func Test_completefunc_first_call_complete_add()
   bwipe!
 endfunc
 
-func Test_complete_fuzzy_match()
+func Test_complete_opt_fuzzy()
   func OnPumChange()
     let g:item = get(v:event, 'completed_item', {})
     let g:word = get(g:item, 'word', v:null)
@@ -2819,8 +2819,66 @@ func Test_complete_fuzzy_match()
   call feedkeys("S\<C-x>\<C-o>fb\<C-n>", 'tx')
   call assert_equal('fooBaz', g:word)
 
-  " avoid breaking default completion behavior
-  set completeopt=fuzzy,menu
+  " test case for nosort option
+  set cot=menuone,menu,noinsert,fuzzy,nosort
+  " "fooBaz" should have a higher score when the leader is "fb".
+  " With "nosort", "foobar" should still be shown first in the popup menu.
+  call feedkeys("S\<C-x>\<C-o>fb", 'tx')
+  call assert_equal('foobar', g:word)
+  call feedkeys("S\<C-x>\<C-o>好", 'tx')
+  call assert_equal("你好吗", g:word)
+
+  set cot+=noselect
+  call feedkeys("S\<C-x>\<C-o>好", 'tx')
+  call assert_equal(v:null, g:word)
+  call feedkeys("S\<C-x>\<C-o>好\<C-N>", 'tx')
+  call assert_equal('你好吗', g:word)
+
+  " "nosort" shouldn't enable fuzzy filtering when "fuzzy" isn't present.
+  set cot=menuone,noinsert,nosort
+  call feedkeys("S\<C-x>\<C-o>fooB\<C-Y>", 'tx')
+  call assert_equal('fooBaz', getline('.'))
+
+  set cot=menuone,fuzzy,nosort
+  func CompAnother()
+    call complete(col('.'), [#{word: "do" }, #{word: "echo"}, #{word: "for (${1:expr1}, ${2:expr2}, ${3:expr3}) {\n\t$0\n}", abbr: "for" }, #{word: "foo"}])
+    return ''
+  endfunc
+  call feedkeys("i\<C-R>=CompAnother()\<CR>\<C-N>\<C-N>", 'tx')
+  call assert_equal("for", g:abbr)
+  call assert_equal(2, g:selected)
+
+  set cot+=noinsert
+  call feedkeys("i\<C-R>=CompAnother()\<CR>f", 'tx')
+  call assert_equal("for", g:abbr)
+  call assert_equal(2, g:selected)
+
+  set cot=menu,menuone,noselect,fuzzy
+  call feedkeys("i\<C-R>=CompAnother()\<CR>\<C-N>\<C-N>\<C-N>\<C-N>", 'tx')
+  call assert_equal("foo", g:word)
+  call feedkeys("i\<C-R>=CompAnother()\<CR>\<C-P>", 'tx')
+  call assert_equal("foo", g:word)
+  call feedkeys("i\<C-R>=CompAnother()\<CR>\<C-P>\<C-P>", 'tx')
+  call assert_equal("for", g:abbr)
+
+  " clean up
+  set omnifunc=
+  bw!
+  set complete& completeopt&
+  autocmd! AAAAA_Group
+  augroup! AAAAA_Group
+  delfunc OnPumChange
+  delfunc Omni_test
+  delfunc Comp
+  unlet g:item
+  unlet g:word
+  unlet g:abbr
+endfunc
+
+func Test_complete_fuzzy_collect()
+  new
+  redraw  " need this to prevent NULL dereference in Nvim
+  set completefuzzycollect=keyword,files,whole_line
   call setline(1, ['hello help hero h'])
   " Use "!" flag of feedkeys() so that ex_normal_busy is not set and
   " ins_compl_check_keys() is not skipped.
@@ -2852,16 +2910,6 @@ func Test_complete_fuzzy_match()
   call feedkeys("A\<C-X>\<C-N>\<C-N>\<Esc>0", 'tx!')
   call assert_equal('你的 我的 我的', getline('.'))
 
-  " respect wrapscan
-  set nowrapscan
-  call setline(1, ["xyz", "yxz", ""])
-  call cursor(3, 1)
-  call feedkeys("Sy\<C-X>\<C-N>\<Esc>0", 'tx!')
-  call assert_equal('y', getline('.'))
-  set wrapscan
-  call feedkeys("Sy\<C-X>\<C-N>\<Esc>0", 'tx!')
-  call assert_equal('xyz', getline('.'))
-
   " fuzzy on file
   call writefile([''], 'fobar', 'D')
   call writefile([''], 'foobar', 'D')
@@ -2877,7 +2925,6 @@ func Test_complete_fuzzy_match()
   call assert_match('../testdir', getline('.'))
 
   " can get completion from other buffer
-  set completeopt=fuzzy,menu,menuone
   vnew
   call setline(1, ["completeness,", "compatibility", "Composite", "Omnipotent"])
   wincmd p
@@ -2929,79 +2976,109 @@ func Test_complete_fuzzy_match()
   call assert_equal('你好 他好', getline('.'))
 
   " issue #15526
-  set completeopt=fuzzy,menuone,menu,noselect
+  set completeopt=menuone,menu,noselect
   call setline(1, ['Text', 'ToText', ''])
   call cursor(3, 1)
   call feedkeys("STe\<C-X>\<C-N>x\<CR>\<Esc>0", 'tx!')
   call assert_equal('Tex', getline(line('.') - 1))
 
-  " test case for nosort option
-  set cot=menuone,menu,noinsert,fuzzy,nosort
-  " "fooBaz" should have a higher score when the leader is "fb".
-  " With "nosort", "foobar" should still be shown first in the popup menu.
-  call feedkeys("S\<C-x>\<C-o>fb", 'tx')
-  call assert_equal('foobar', g:word)
-  call feedkeys("S\<C-x>\<C-o>好", 'tx')
-  call assert_equal("你好吗", g:word)
+  bw!
+  bw!
+  set completeopt& cfc& cpt&
+endfunc
+
+func Test_cfc_with_longest()
+  new
+  set completefuzzycollect=keyword,files,whole_line
+  set completeopt=menu,menuone,longest,fuzzy
+
+  " keyword
+  exe "normal ggdGShello helio think h\<C-X>\<C-N>\<ESC>"
+  call assert_equal("hello helio think hel", getline('.'))
+  exe "normal hello helio think h\<C-X>\<C-P>\<ESC>"
+  call assert_equal("hello helio think hel", getline('.'))
+
+  " skip non-consecutive prefixes
+  exe "normal ggdGShello helio heo\<C-X>\<C-N>\<ESC>"
+  call assert_equal("hello helio heo", getline('.'))
+
+  " kdcit
+  call writefile(['help'], 'test_keyword.txt', 'D')
+  set complete=ktest_keyword.txt
+  exe "normal ggdGSh\<C-N>\<ESC>"
+  " auto insert help when only have one match
+  call assert_equal("help", getline('.'))
+  call writefile(['hello', 'help', 'think'], 'xtest_keyword.txt', 'D')
+  set complete=kxtest_keyword.txt
+  " auto insert hel
+  exe "normal ggdGSh\<C-N>\<ESC>"
+  call assert_equal("hel", getline('.'))
+
+  " line start with a space
+  call writefile([' hello'], 'test_case1.txt', 'D')
+  set complete=ktest_case1.txt
+  exe "normal ggdGSh\<C-N>\<ESC>"
+  call assert_equal("hello", getline('.'))
 
-  set cot+=noselect
-  call feedkeys("S\<C-x>\<C-o>好", 'tx')
-  call assert_equal(v:null, g:word)
-  call feedkeys("S\<C-x>\<C-o>好\<C-N>", 'tx')
-  call assert_equal('你好吗', g:word)
+  " multiple matches
+  set complete=ktest_case2.txt
+  call writefile([' hello help what'], 'test_case2.txt', 'D')
+  exe "normal ggdGSh\<C-N>\<C-N>\<C-N>\<C-N>\<ESC>"
+  call assert_equal("what", getline('.'))
+
+  " multiple lines of matches
+  set complete=ktest_case3.txt
+  call writefile([' hello help what', 'hola', '     hey'], 'test_case3.txt', 'D')
+  exe "normal ggdGSh\<C-N>\<C-N>\<ESC>"
+  call assert_equal("hey", getline('.'))
+  exe "normal ggdGSh\<C-N>\<C-N>\<C-N>\<C-N>\<ESC>"
+  call assert_equal("hola", getline('.'))
+
+  set complete=ktest_case4.txt
+  call writefile(['  auto int   enum register', 'why'], 'test_case4.txt', 'D')
+  exe "normal ggdGSe\<C-N>\<C-N>\<ESC>"
+  call assert_equal("enum", getline('.'))
+  set complete&
 
-  " "nosort" shouldn't enable fuzzy filtering when "fuzzy" isn't present.
-  set cot=menuone,noinsert,nosort
-  call feedkeys("S\<C-x>\<C-o>fooB\<C-Y>", 'tx')
-  call assert_equal('fooBaz', getline('.'))
+  " file
+  call writefile([''], 'hello', 'D')
+  call writefile([''], 'helio', 'D')
+  exe "normal ggdGS./h\<C-X>\<C-f>\<ESC>"
+  call assert_equal('./hel', getline('.'))
 
-  set cot=menuone,fuzzy,nosort
-  func CompAnother()
-    call complete(col('.'), [#{word: "do" }, #{word: "echo"}, #{word: "for (${1:expr1}, ${2:expr2}, ${3:expr3}) {\n\t$0\n}", abbr: "for" }, #{word: "foo"}])
-    return ''
-  endfunc
-  call feedkeys("i\<C-R>=CompAnother()\<CR>\<C-N>\<C-N>", 'tx')
-  call assert_equal("for", g:abbr)
-  call assert_equal(2, g:selected)
+  " word
+  call setline(1, ['what do you think', 'why i have that', ''])
+  call cursor(3,1)
+  call feedkeys("Sw\<C-X>\<C-l>\<C-N>\<Esc>0", 'tx!')
+  call assert_equal('wh', getline('.'))
 
-  set cot+=noinsert
-  call feedkeys("i\<C-R>=CompAnother()\<CR>f", 'tx')
-  call assert_equal("for", g:abbr)
-  call assert_equal(2, g:selected)
+  exe "normal ggdG"
+  " auto complete when only one match
+  exe "normal Shello\<CR>h\<C-X>\<C-N>\<esc>"
+  call assert_equal('hello', getline('.'))
+  exe "normal Sh\<C-N>\<C-P>\<esc>"
+  call assert_equal('hello', getline('.'))
 
-  set cot=menu,menuone,noselect,fuzzy
-  call feedkeys("i\<C-R>=CompAnother()\<CR>\<C-N>\<C-N>\<C-N>\<C-N>", 'tx')
-  call assert_equal("foo", g:word)
-  call feedkeys("i\<C-R>=CompAnother()\<CR>\<C-P>", 'tx')
-  call assert_equal("foo", g:word)
-  call feedkeys("i\<C-R>=CompAnother()\<CR>\<C-P>\<C-P>", 'tx')
-  call assert_equal("for", g:abbr)
+  exe "normal Shello\<CR>h\<C-X>\<C-N>\<Esc>cch\<C-X>\<C-N>\<Esc>"
+  call assert_equal('hello', getline('.'))
+
+  " continue search for new leader after insert common prefix
+  exe "normal ohellokate\<CR>h\<C-X>\<C-N>k\<C-y>\<esc>"
+  call assert_equal('hellokate', getline('.'))
 
-  " clean up
-  set omnifunc=
-  bw!
   bw!
-  set complete& completeopt&
-  autocmd! AAAAA_Group
-  augroup! AAAAA_Group
-  delfunc OnPumChange
-  delfunc Omni_test
-  delfunc Comp
-  delfunc CompAnother
-  unlet g:item
-  unlet g:word
-  unlet g:selected
-  unlet g:abbr
+  set completeopt&
+  set completefuzzycollect&
 endfunc
 
-func Test_complete_fuzzy_with_completeslash()
+func Test_completefuzzycollect_with_completeslash()
   CheckMSWindows
 
   call writefile([''], 'fobar', 'D')
   let orig_shellslash = &shellslash
   set cpt&
   new
-  set completeopt+=fuzzy
+  set completefuzzycollect=files
   set noshellslash
 
   " Test with completeslash unset
@@ -3023,6 +3100,7 @@ func Test_complete_fuzzy_with_completeslash()
   " Reset and clean up
   let &shellslash = orig_shellslash
   set completeslash=
+  set completefuzzycollect&
   %bw!
 endfunc
 
diff --git a/test/old/testdir/test_popup.vim b/test/old/testdir/test_popup.vim
index 51b6861e11..8f81db6213 100644
--- a/test/old/testdir/test_popup.vim
+++ b/test/old/testdir/test_popup.vim
@@ -1501,22 +1501,6 @@ func Test_pum_highlights_match()
   call VerifyScreenDump(buf, 'Test_pum_highlights_09', {})
   call term_sendkeys(buf, "o\<BS>\<C-R>=Comp()\<CR>")
   call VerifyScreenDump(buf, 'Test_pum_highlights_09', {})
-
-  " issue #15095 wrong select
-  call term_sendkeys(buf, "\<ESC>:set completeopt=fuzzy,menu\<CR>")
-  call TermWait(buf)
-  call term_sendkeys(buf, "S hello helio hero h\<C-X>\<C-P>")
-  call TermWait(buf, 50)
-  call VerifyScreenDump(buf, 'Test_pum_highlights_10', {})
-
-  call term_sendkeys(buf, "\<ESC>S hello helio hero h\<C-X>\<C-P>\<C-P>")
-  call TermWait(buf, 50)
-  call VerifyScreenDump(buf, 'Test_pum_highlights_11', {})
-
-  " issue #15357
-  call term_sendkeys(buf, "\<ESC>S/non_existing_folder\<C-X>\<C-F>")
-  call TermWait(buf, 50)
-  call VerifyScreenDump(buf, 'Test_pum_highlights_15', {})
   call term_sendkeys(buf, "\<C-E>\<Esc>")
 
   call term_sendkeys(buf, ":hi PmenuMatchSel ctermfg=14 ctermbg=NONE\<CR>")
@@ -1530,7 +1514,34 @@ func Test_pum_highlights_match()
 
   call term_sendkeys(buf, "\<C-E>\<Esc>")
   call TermWait(buf)
+  call StopVimInTerminal(buf)
+endfunc
 
+func Test_pum_completefuzzycollect()
+  CheckScreendump
+  let lines =<< trim END
+    set completefuzzycollect=keyword,files
+    set completeopt=menu,menuone
+  END
+  call writefile(lines, 'Xscript', 'D')
+  let  buf = RunVimInTerminal('-S Xscript', {})
+
+  " issue #15095 wrong select
+  call term_sendkeys(buf, "S hello helio hero h\<C-X>\<C-P>")
+  call TermWait(buf, 50)
+  call VerifyScreenDump(buf, 'Test_pum_completefuzzycollect_01', {})
+
+  call term_sendkeys(buf, "\<ESC>S hello helio hero h\<C-X>\<C-P>\<C-P>")
+  call TermWait(buf, 50)
+  call VerifyScreenDump(buf, 'Test_pum_completefuzzycollect_02', {})
+
+  " issue #15357
+  call term_sendkeys(buf, "\<ESC>S/non_existing_folder\<C-X>\<C-F>")
+  call TermWait(buf, 50)
+  call VerifyScreenDump(buf, 'Test_pum_completefuzzycollect_03', {})
+  call term_sendkeys(buf, "\<C-E>\<Esc>")
+
+  call TermWait(buf)
   call StopVimInTerminal(buf)
 endfunc