vim-patch:9.1.0810: cannot easily adjust the |:find| command

Problem:  cannot easily adjust the |:find| command
Solution: Add support for the 'findexpr' option (Yegappan Lakshmanan)

closes: vim/vim#15901
closes: vim/vim#15905

https://github.com/vim/vim/commit/aeb1c97db5b9de4f4903e7f288f2aa5ad6c49440

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

11 files changed, 202 insertions, 30 deletions

diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 2142b5b298..42cc745fe6 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -2049,6 +2049,7 @@ void free_buf_options(buf_T *buf, bool free_p_ff)
   clear_string_option(&buf->b_p_indk);
   clear_string_option(&buf->b_p_fp);
   clear_string_option(&buf->b_p_fex);
+  clear_string_option(&buf->b_p_fexpr);
   clear_string_option(&buf->b_p_kp);
   clear_string_option(&buf->b_p_mps);
   clear_string_option(&buf->b_p_fo);
diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index 134d69de96..88e8d59faa 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -608,6 +608,7 @@ struct file_buffer {
   char *b_p_mp;                 ///< 'makeprg' local value
   char *b_p_efm;                ///< 'errorformat' local value
   char *b_p_ep;                 ///< 'equalprg' local value
+  char *b_p_fexpr;              ///< 'findexpr' local value
   char *b_p_path;               ///< 'path' local value
   int b_p_ar;                   ///< 'autoread' local value
   char *b_p_tags;               ///< 'tags' local value
diff --git a/src/nvim/errors.h b/src/nvim/errors.h
index 39095db952..bea56541a2 100644
--- a/src/nvim/errors.h
+++ b/src/nvim/errors.h
@@ -156,6 +156,11 @@ EXTERN const char e_luv_api_disabled[] INIT(= N_("E5560: %s must not be called i
 EXTERN const char e_floatonly[] INIT(= N_("E5601: Cannot close window, only floating window would remain"));
 EXTERN const char e_floatexchange[] INIT(= N_("E5602: Cannot exchange or rotate float"));
 
+EXTERN const char e_cant_find_directory_str_in_cdpath[] INIT(= N_("E344: Can't find directory \"%s\" in cdpath"));
+EXTERN const char e_cant_find_file_str_in_path[] INIT(= N_("E345: Can't find file \"%s\" in path"));
+EXTERN const char e_no_more_directory_str_found_in_cdpath[] INIT(= N_("E346: No more directory \"%s\" found in cdpath"));
+EXTERN const char e_no_more_file_str_found_in_path[] INIT(= N_("E347: No more file \"%s\" found in path"));
+
 EXTERN const char e_cannot_define_autocommands_for_all_events[] INIT(= N_("E1155: Cannot define autocommands for ALL events"));
 
 EXTERN const char e_resulting_text_too_long[] INIT(= N_("E1240: Resulting text too long"));
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 93cff80bd4..6a455f70a6 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -2631,7 +2631,7 @@ static int may_call_simple_func(const char *arg, typval_T *rettv)
 
 /// Handle zero level expression with optimization for a simple function call.
 /// Same arguments and return value as eval0().
-static int eval0_simple_funccal(char *arg, typval_T *rettv, exarg_T *eap, evalarg_T *const evalarg)
+int eval0_simple_funccal(char *arg, typval_T *rettv, exarg_T *eap, evalarg_T *const evalarg)
 {
   int r = may_call_simple_func(arg, rettv);
 
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 293aaac036..5c61399003 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -5165,6 +5165,90 @@ static void ex_wrongmodifier(exarg_T *eap)
   eap->errmsg = _(e_invcmd);
 }
 
+/// Evaluate the 'findexpr' expression and return the result.  When evaluating
+/// the expression, v:fname is set to the ":find" command argument.
+static list_T *eval_findexpr(const char *ptr, size_t len)
+{
+  const sctx_T saved_sctx = current_sctx;
+  bool use_sandbox = false;
+
+  char *findexpr;
+  if (*curbuf->b_p_fexpr == NUL) {
+    use_sandbox = was_set_insecurely(curwin, kOptFindexpr, OPT_GLOBAL);
+    findexpr = p_fexpr;
+  } else {
+    use_sandbox = was_set_insecurely(curwin, kOptFindexpr, OPT_LOCAL);
+    findexpr = curbuf->b_p_fexpr;
+  }
+
+  set_vim_var_string(VV_FNAME, ptr, (ptrdiff_t)len);
+  current_sctx = curbuf->b_p_script_ctx[BV_FEXPR].script_ctx;
+
+  char *arg = skipwhite(findexpr);
+
+  if (use_sandbox) {
+    sandbox++;
+  }
+  textlock++;
+
+  // Evaluate the expression.  If the expression is "FuncName()" call the
+  // function directly.
+  typval_T tv;
+  list_T *retlist = NULL;
+  if (eval0_simple_funccal(arg, &tv, NULL, &EVALARG_EVALUATE) == FAIL) {
+    retlist = NULL;
+  } else {
+    if (tv.v_type == VAR_LIST) {
+      retlist = tv_list_copy(NULL, tv.vval.v_list, true, get_copyID());
+    }
+    tv_clear(&tv);
+  }
+  if (use_sandbox) {
+    sandbox--;
+  }
+  textlock--;
+  clear_evalarg(&EVALARG_EVALUATE, NULL);
+
+  set_vim_var_string(VV_FNAME, NULL, 0);
+  current_sctx = saved_sctx;
+
+  return retlist;
+}
+
+/// Use 'findexpr' to find file 'findarg'.  The 'count' argument is used to find
+/// the n'th matching file.
+static char *findexpr_find_file(char *findarg, size_t findarg_len, int count)
+{
+  char *ret_fname = NULL;
+
+  const char cc = findarg[findarg_len];
+  findarg[findarg_len] = NUL;
+
+  list_T *fname_list = eval_findexpr(findarg, findarg_len);
+  int fname_count = tv_list_len(fname_list);
+
+  if (fname_count == 0) {
+    semsg(_(e_cant_find_file_str_in_path), findarg);
+  } else {
+    if (count > fname_count) {
+      semsg(_(e_no_more_file_str_found_in_path), findarg);
+    } else {
+      listitem_T *li = tv_list_find(fname_list, count - 1);
+      if (li != NULL && TV_LIST_ITEM_TV(li)->v_type == VAR_STRING) {
+        ret_fname = xstrdup(TV_LIST_ITEM_TV(li)->vval.v_string);
+      }
+    }
+  }
+
+  if (fname_list != NULL) {
+    tv_list_free(fname_list);
+  }
+
+  findarg[findarg_len] = cc;
+
+  return ret_fname;
+}
+
 /// :sview [+command] file       split window with new file, read-only
 /// :split [[+command] file]     split window with current or new file
 /// :vsplit [[+command] file]    split window vertically with current or new file
@@ -5196,13 +5280,17 @@ void ex_splitview(exarg_T *eap)
   }
 
   if (eap->cmdidx == CMD_sfind || eap->cmdidx == CMD_tabfind) {
-    char *file_to_find = NULL;
-    char *search_ctx = NULL;
-    fname = find_file_in_path(eap->arg, strlen(eap->arg),
-                              FNAME_MESS, true, curbuf->b_ffname,
-                              &file_to_find, &search_ctx);
-    xfree(file_to_find);
-    vim_findfile_cleanup(search_ctx);
+    if (*get_findexpr() != NUL) {
+      fname = findexpr_find_file(eap->arg, strlen(eap->arg),
+                                 eap->addr_count > 0 ? eap->line2 : 1);
+    } else {
+      char *file_to_find = NULL;
+      char *search_ctx = NULL;
+      fname = find_file_in_path(eap->arg, strlen(eap->arg), FNAME_MESS, true,
+                                curbuf->b_ffname, &file_to_find, &search_ctx);
+      xfree(file_to_find);
+      vim_findfile_cleanup(search_ctx);
+    }
     if (fname == NULL) {
       goto theend;
     }
@@ -5398,23 +5486,28 @@ static void ex_find(exarg_T *eap)
     return;
   }
 
-  char *file_to_find = NULL;
-  char *search_ctx = NULL;
-  char *fname = find_file_in_path(eap->arg, strlen(eap->arg),
-                                  FNAME_MESS, true, curbuf->b_ffname,
-                                  &file_to_find, &search_ctx);
-  if (eap->addr_count > 0) {
-    // Repeat finding the file "count" times.  This matters when it appears
-    // several times in the path.
-    linenr_T count = eap->line2;
-    while (fname != NULL && --count > 0) {
-      xfree(fname);
-      fname = find_file_in_path(NULL, 0, FNAME_MESS, false, curbuf->b_ffname,
-                                &file_to_find, &search_ctx);
+  char *fname = NULL;
+  if (*get_findexpr() != NUL) {
+    fname = findexpr_find_file(eap->arg, strlen(eap->arg),
+                               eap->addr_count > 0 ? eap->line2 : 1);
+  } else {
+    char *file_to_find = NULL;
+    char *search_ctx = NULL;
+    fname = find_file_in_path(eap->arg, strlen(eap->arg), FNAME_MESS, true,
+                              curbuf->b_ffname, &file_to_find, &search_ctx);
+    if (eap->addr_count > 0) {
+      // Repeat finding the file "count" times.  This matters when it appears
+      // several times in the path.
+      linenr_T count = eap->line2;
+      while (fname != NULL && --count > 0) {
+        xfree(fname);
+        fname = find_file_in_path(NULL, 0, FNAME_MESS, false,
+                                  curbuf->b_ffname, &file_to_find, &search_ctx);
+      }
     }
+    xfree(file_to_find);
+    vim_findfile_cleanup(search_ctx);
   }
-  xfree(file_to_find);
-  vim_findfile_cleanup(search_ctx);
 
   if (fname == NULL) {
     return;
diff --git a/src/nvim/file_search.c b/src/nvim/file_search.c
index cdfd281718..aeaf448a05 100644
--- a/src/nvim/file_search.c
+++ b/src/nvim/file_search.c
@@ -1489,15 +1489,15 @@ char *find_file_in_path_option(char *ptr, size_t len, int options, int first, ch
   if (file_name == NULL && (options & FNAME_MESS)) {
     if (first == true) {
       if (find_what == FINDFILE_DIR) {
-        semsg(_("E344: Can't find directory \"%s\" in cdpath"), *file_to_find);
+        semsg(_(e_cant_find_directory_str_in_cdpath), *file_to_find);
       } else {
-        semsg(_("E345: Can't find file \"%s\" in path"), *file_to_find);
+        semsg(_(e_cant_find_file_str_in_path), *file_to_find);
       }
     } else {
       if (find_what == FINDFILE_DIR) {
-        semsg(_("E346: No more directory \"%s\" found in cdpath"), *file_to_find);
+        semsg(_(e_no_more_directory_str_found_in_cdpath), *file_to_find);
       } else {
-        semsg(_("E347: No more file \"%s\" found in path"), *file_to_find);
+        semsg(_(e_no_more_file_str_found_in_path), *file_to_find);
       }
     }
   }
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 7c32c99d0e..65f03ca77f 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -4530,6 +4530,8 @@ void *get_varp_scope_from(vimoption_T *p, int scope, buf_T *buf, win_T *win)
     switch ((int)p->indir) {
     case PV_FP:
       return &(buf->b_p_fp);
+    case PV_FEXPR:
+      return &(buf->b_p_fexpr);
     case PV_EFM:
       return &(buf->b_p_efm);
     case PV_GP:
@@ -4651,6 +4653,8 @@ void *get_varp_from(vimoption_T *p, buf_T *buf, win_T *win)
     return *buf->b_p_tsrfu != NUL ? &(buf->b_p_tsrfu) : p->var;
   case PV_FP:
     return *buf->b_p_fp != NUL ? &(buf->b_p_fp) : p->var;
+  case PV_FEXPR:
+    return *buf->b_p_fexpr != NUL ? &(buf->b_p_fexpr) : p->var;
   case PV_EFM:
     return *buf->b_p_efm != NUL ? &(buf->b_p_efm) : p->var;
   case PV_GP:
@@ -4922,6 +4926,15 @@ char *get_equalprg(void)
   return curbuf->b_p_ep;
 }
 
+/// Get the value of 'findexpr', either the buffer-local one or the global one.
+char *get_findexpr(void)
+{
+  if (*curbuf->b_p_fexpr == NUL) {
+    return p_fexpr;
+  }
+  return curbuf->b_p_fexpr;
+}
+
 /// Copy options from one window to another.
 /// Used when splitting a window.
 void win_copy_options(win_T *wp_from, win_T *wp_to)
@@ -5320,6 +5333,8 @@ void buf_copy_options(buf_T *buf, int flags)
       buf->b_p_mp = empty_string_option;
       buf->b_p_efm = empty_string_option;
       buf->b_p_ep = empty_string_option;
+      buf->b_p_fexpr = xstrdup(p_fexpr);
+      COPY_OPT_SCTX(buf, BV_FEXPR);
       buf->b_p_kp = empty_string_option;
       buf->b_p_path = empty_string_option;
       buf->b_p_tags = empty_string_option;
diff --git a/src/nvim/option_vars.h b/src/nvim/option_vars.h
index 5b630117ab..a88b51dae7 100644
--- a/src/nvim/option_vars.h
+++ b/src/nvim/option_vars.h
@@ -451,6 +451,7 @@ EXTERN char *p_ffs;             ///< 'fileformats'
 EXTERN int p_fic;               ///< 'fileignorecase'
 EXTERN char *p_ft;              ///< 'filetype'
 EXTERN char *p_fcs;             ///< 'fillchar'
+EXTERN char *p_fexpr;           ///< 'findexpr'
 EXTERN int p_fixeol;            ///< 'fixendofline'
 EXTERN char *p_fcl;             ///< 'foldclose'
 EXTERN OptInt p_fdls;           ///< 'foldlevelstart'
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index a891d18364..65401fb3a9 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -2906,6 +2906,59 @@ return {
       varname = 'p_fcs',
     },
     {
+      abbreviation = 'fexpr',
+      cb = 'did_set_optexpr',
+      defaults = { if_true = '' },
+      desc = [=[
+        Expression that is evaluated to obtain the filename(s) for the |:find|
+        command.  When this option is empty, the internal |file-searching|
+        mechanism is used.
+
+        While evaluating the expression, the |v:fname| variable is set to the
+        argument of the |:find| command.
+
+        The expression is evaluated only once per |:find| command invocation.
+        The expression can process all the directories specified in 'path'.
+
+        If a match is found, the expression should return a |List| containing
+        one or more file names.  If a match is not found, the expression
+        should return an empty List.
+
+        If any errors are encountered during the expression evaluation, an
+        empty List is used as the return value.
+
+        Using a function call without arguments is faster |expr-option-function|
+
+        It is not allowed to change text or jump to another window while
+        evaluating 'findexpr' |textlock|.
+
+        This option cannot be set from a |modeline| or in the |sandbox|, for
+        security reasons.
+
+        Examples:
+        >vim
+            " Use glob()
+            func FindExprGlob()
+        	return glob(v:fname, v:false, v:true)
+            endfunc
+            set findexpr=FindExprGlob()
+
+            " Use the 'git ls-files' output
+            func FindGitFiles()
+        	let fnames = systemlist('git ls-files')
+        	return fnames->filter('v:val =~? v:fname')
+            endfunc
+            set findexpr=FindGitFiles()
+        <
+      ]=],
+      full_name = 'findexpr',
+      scope = { 'global', 'buffer' },
+      secure = true,
+      short_desc = N_('expression used for :find'),
+      type = 'string',
+      varname = 'p_fexpr',
+    },
+    {
       abbreviation = 'fixeol',
       cb = 'did_set_eof_eol_fixeol_bomb',
       defaults = { if_true = true },
diff --git a/src/nvim/optionstr.c b/src/nvim/optionstr.c
index e07fcf2f0e..c66849800c 100644
--- a/src/nvim/optionstr.c
+++ b/src/nvim/optionstr.c
@@ -233,6 +233,7 @@ void check_buf_options(buf_T *buf)
   check_string_option(&buf->b_p_mp);
   check_string_option(&buf->b_p_efm);
   check_string_option(&buf->b_p_ep);
+  check_string_option(&buf->b_p_fexpr);
   check_string_option(&buf->b_p_path);
   check_string_option(&buf->b_p_tags);
   check_string_option(&buf->b_p_tfu);
@@ -1885,8 +1886,9 @@ int expand_set_nrformats(optexpand_T *args, int *numMatches, char ***matches)
                                matches);
 }
 
-/// One of the '*expr' options is changed:, 'diffexpr', 'foldexpr', 'foldtext',
-/// 'formatexpr', 'includeexpr', 'indentexpr', 'patchexpr' and 'charconvert'.
+/// One of the '*expr' options is changed:, 'diffexpr', 'findexpr',
+/// 'foldexpr', 'foldtext', 'formatexpr', 'includeexpr', 'indentexpr',
+/// 'patchexpr' and 'charconvert'.
 const char *did_set_optexpr(optset_T *args)
 {
   char **varp = (char **)args->os_varp;
diff --git a/src/nvim/vvars.lua b/src/nvim/vvars.lua
index ad139bbbfe..5c9f0f9e27 100644
--- a/src/nvim/vvars.lua
+++ b/src/nvim/vvars.lua
@@ -284,7 +284,8 @@ M.vars = {
     type = 'string',
     desc = [=[
       When evaluating 'includeexpr': the file name that was
-      detected.  Empty otherwise.
+      detected.  When evaluating 'findexpr': the argument passed to
+      the |:find| command.  Empty otherwise.
     ]=],
   },
   fname_diff = {