vim-patch:8.2.3848: cannot use reduce() for a string

Problem:    Cannot use reduce() for a string.
Solution:   Make reduce() work with a string. (Naruhiko Nishino, closes vim/vim#9366)

0ccb5842f5

Omit tv_get_first_char() as it doesn't really save much code.

Co-authored-by: rbtnn <naru123456789@gmail.com>

runtime/doc/builtin.txt

@@ -5514,9 +5514,9 @@ readfile({fname} [, {type} [, {max}]])                              *readfile()*
 
 reduce({object}, {func} [, {initial}])                           *reduce()* *E998*
 		{func} is called for every item in {object}, which can be a
-		|List| or a |Blob|.  {func} is called with two arguments: the
+		|String|, |List| or a |Blob|.  {func} is called with two arguments:
-		result so far and current item.  After processing all items
+		the result so far and current item.  After processing all
-		the result is returned.
+		items the result is returned.
 
 		{initial} is the initial result.  When omitted, the first item
 		in {object} is used and {func} is first called for the second
@@ -5527,6 +5527,7 @@ reduce({object}, {func} [, {initial}])                           *reduce()* *E99
 			echo reduce([1, 3, 5], { acc, val -> acc + val })
 			echo reduce(['x', 'y'], { acc, val -> acc .. val }, 'a')
 			echo reduce(0z1122, { acc, val -> 2 * acc + val })
+			echo reduce('xyz', { acc, val -> acc .. ',' .. val })
 <
 
 reg_executing()                                                *reg_executing()*

runtime/lua/vim/_meta/vimfn.lua

@@ -6551,9 +6551,9 @@ function vim.fn.readdir(directory, expr) end
 function vim.fn.readfile(fname, type, max) end
 
 --- {func} is called for every item in {object}, which can be a
---- |List| or a |Blob|.  {func} is called with two arguments: the
+--- |String|, |List| or a |Blob|.  {func} is called with two arguments:
---- result so far and current item.  After processing all items
+--- the result so far and current item.  After processing all
---- the result is returned.
+--- items the result is returned.
 ---
 --- {initial} is the initial result.  When omitted, the first item
 --- in {object} is used and {func} is first called for the second
@@ -6564,6 +6564,7 @@ function vim.fn.readfile(fname, type, max) end
 ---   echo reduce([1, 3, 5], { acc, val -> acc + val })
 ---   echo reduce(['x', 'y'], { acc, val -> acc .. val }, 'a')
 ---   echo reduce(0z1122, { acc, val -> 2 * acc + val })
+---   echo reduce('xyz', { acc, val -> acc .. ',' .. val })
 --- <
 ---
 --- @param object any

src/nvim/eval.c

@@ -108,7 +108,7 @@ static const char e_dot_can_only_be_used_on_dictionary_str[]
   = N_("E1203: Dot can only be used on a dictionary: %s");
 static const char e_empty_function_name[]
   = N_("E1192: Empty function name");
-static char e_argument_of_str_must_be_list_string_dictionary_or_blob[]
+static const char e_argument_of_str_must_be_list_string_dictionary_or_blob[]
   = N_("E1250: Argument of %s must be a List, String, Dictionary or Blob");
 
 static char * const namespace_char = "abglstvw";
@@ -5206,7 +5206,6 @@ static void filter_map(typval_T *argvars, typval_T *rettv, filtermap_T filtermap
       int len;
       for (const char *p = tv_get_string(&argvars[0]); *p != NUL; p += len) {
         len = utfc_ptr2len(p);
-
         typval_T tv = {
           .v_type = VAR_STRING,
           .v_lock = VAR_UNLOCKED,

src/nvim/eval.lua

@@ -7876,9 +7876,9 @@ M.funcs = {
     tags = { 'E998' },
     desc = [=[
       {func} is called for every item in {object}, which can be a
-      |List| or a |Blob|.  {func} is called with two arguments: the
+      |String|, |List| or a |Blob|.  {func} is called with two arguments:
-      result so far and current item.  After processing all items
+      the result so far and current item.  After processing all
-      the result is returned.
+      items the result is returned.
 
       {initial} is the initial result.  When omitted, the first item
       in {object} is used and {func} is first called for the second
@@ -7889,6 +7889,7 @@ M.funcs = {
       	echo reduce([1, 3, 5], { acc, val -> acc + val })
       	echo reduce(['x', 'y'], { acc, val -> acc .. val }, 'a')
       	echo reduce(0z1122, { acc, val -> 2 * acc + val })
+      	echo reduce('xyz', { acc, val -> acc .. ',' .. val })
       <
     ]=],
     name = 'reduce',

src/nvim/eval/funcs.c

@@ -150,8 +150,12 @@ static const char *e_invalwindow = N_("E957: Invalid window number");
 static const char e_invalid_submatch_number_nr[]
   = N_("E935: Invalid submatch number: %d");
 static const char *e_reduceempty = N_("E998: Reduce of an empty %s with no initial value");
+static const char e_string_list_or_blob_required[]
+  = N_("E1098: String, List or Blob required");
 static const char e_missing_function_argument[]
   = N_("E1132: Missing function argument");
+static const char e_string_expected_for_argument_nr[]
+  = N_("E1253: String expected for argument %d");
 
 /// Dummy va_list for passing to vim_snprintf
 ///
@@ -6168,11 +6172,16 @@ static void f_reverse(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 }
 
 /// "reduce(list, { accumulator, element -> value } [, initial])" function
+/// "reduce(blob, { accumulator, element -> value } [, initial])" function
+/// "reduce(string, { accumulator, element -> value } [, initial])" function
 static void f_reduce(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
-  if (argvars[0].v_type != VAR_LIST && argvars[0].v_type != VAR_BLOB) {
+  const int called_emsg_start = called_emsg;
-    emsg(_(e_listblobreq));
+
-    return;
+  if (argvars[0].v_type != VAR_STRING
+      && argvars[0].v_type != VAR_LIST
+      && argvars[0].v_type != VAR_BLOB) {
+    emsg(_(e_string_list_or_blob_required));
   }
 
   const char *func_name;
@@ -6217,7 +6226,6 @@ static void f_reduce(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
     if (l != NULL) {
       const VarLockStatus prev_locked = tv_list_locked(l);
-      const int called_emsg_start = called_emsg;
 
       tv_list_set_lock(l, VAR_FIXED);  // disallow the list changing here
       for (; li != NULL; li = TV_LIST_ITEM_NEXT(l, li)) {
@@ -6232,6 +6240,44 @@ static void f_reduce(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
       }
       tv_list_set_lock(l, prev_locked);
     }
+  } else if (argvars[0].v_type == VAR_STRING) {
+    const char *p = tv_get_string(&argvars[0]);
+    int len;
+
+    if (argvars[2].v_type == VAR_UNKNOWN) {
+      if (*p == NUL) {
+        semsg(_(e_reduceempty), "String");
+        return;
+      }
+      len = utfc_ptr2len(p);
+      *rettv = (typval_T){
+        .v_type = VAR_STRING,
+        .v_lock = VAR_UNLOCKED,
+        .vval.v_string = xstrnsave(p, (size_t)len),
+      };
+      p += len;
+    } else if (argvars[2].v_type != VAR_STRING) {
+      semsg(_(e_string_expected_for_argument_nr), 3);
+      return;
+    } else {
+      tv_copy(&argvars[2], rettv);
+    }
+
+    for (; *p != NUL; p += len) {
+      argv[0] = *rettv;
+      len = utfc_ptr2len(p);
+      argv[1] = (typval_T){
+        .v_type = VAR_STRING,
+        .v_lock = VAR_UNLOCKED,
+        .vval.v_string = xstrnsave(p, (size_t)len),
+      };
+      const int r = call_func(func_name, -1, rettv, 2, argv, &funcexe);
+      tv_clear(&argv[0]);
+      tv_clear(&argv[1]);
+      if (r == FAIL || called_emsg != called_emsg_start) {
+        break;
+      }
+    }
   } else {
     const blob_T *const b = argvars[0].vval.v_blob;
     int i;

test/old/testdir/test_listdict.vim

@@ -1,4 +1,5 @@
 " Tests for the List and Dict types
+scriptencoding utf-8
 
 source vim9.vim
 
@@ -900,7 +901,7 @@ func Test_reverse_sort_uniq()
   call assert_fails("call sort([1, 2], function('min'))", "E118:")
 endfunc
 
-" reduce a list or a blob
+" reduce a list, blob or string
 func Test_reduce()
   let lines =<< trim END
       call assert_equal(1, reduce([], LSTART acc, val LMIDDLE acc + val LEND, 1))
@@ -923,6 +924,16 @@ func Test_reduce()
 
       call assert_equal(0xff, reduce(0zff, LSTART acc, val LMIDDLE acc + val LEND))
       call assert_equal(2 * (2 * 0xaf + 0xbf) + 0xcf, reduce(0zAFBFCF, LSTART acc, val LMIDDLE 2 * acc + val LEND))
+
+      call assert_equal('x,y,z', 'xyz'->reduce(LSTART acc, val LMIDDLE acc .. ',' .. val LEND))
+      call assert_equal('', ''->reduce(LSTART acc, val LMIDDLE acc .. ',' .. val LEND, ''))
+      call assert_equal('あ,い,う,え,お,😊,💕', 'あいうえお😊💕'->reduce(LSTART acc, val LMIDDLE acc .. ',' .. val LEND))
+      call assert_equal('😊,あ,い,う,え,お,💕', 'あいうえお💕'->reduce(LSTART acc, val LMIDDLE acc .. ',' .. val LEND, '😊'))
+      call assert_equal('ऊ,ॠ,ॡ', reduce('ऊॠॡ', LSTART acc, val LMIDDLE acc .. ',' .. val LEND))
+      call assert_equal('c,à,t', reduce('càt', LSTART acc, val LMIDDLE acc .. ',' .. val LEND))
+      call assert_equal('Å,s,t,r,ö,m', reduce('Åström', LSTART acc, val LMIDDLE acc .. ',' .. val LEND))
+      call assert_equal('Å,s,t,r,ö,m', reduce('Åström', LSTART acc, val LMIDDLE acc .. ',' .. val LEND))
+      call assert_equal(',a,b,c', reduce('abc', LSTART acc, val LMIDDLE acc .. ',' .. val LEND, v:_null_string))
   END
   call CheckLegacyAndVim9Success(lines)
 
@@ -931,13 +942,23 @@ func Test_reduce()
 
   call assert_fails("call reduce([], { acc, val -> acc + val })", 'E998: Reduce of an empty List with no initial value')
   call assert_fails("call reduce(0z, { acc, val -> acc + val })", 'E998: Reduce of an empty Blob with no initial value')
+  call assert_fails("call reduce('', { acc, val -> acc + val })", 'E998: Reduce of an empty String with no initial value')
+  call assert_fails("call reduce(v:_null_string, { acc, val -> acc + val })", 'E998: Reduce of an empty String with no initial value')
 
-  call assert_fails("call reduce({}, { acc, val -> acc + val }, 1)", 'E897:')
+  call assert_fails("call reduce({}, { acc, val -> acc + val }, 1)", 'E1098:')
-  call assert_fails("call reduce(0, { acc, val -> acc + val }, 1)", 'E897:')
+  call assert_fails("call reduce(0, { acc, val -> acc + val }, 1)", 'E1098:')
-  call assert_fails("call reduce('', { acc, val -> acc + val }, 1)", 'E897:')
   call assert_fails("call reduce([1, 2], 'Xdoes_not_exist')", 'E117:')
   call assert_fails("echo reduce(0z01, { acc, val -> 2 * acc + val }, '')", 'E39:')
 
+  " call assert_fails("vim9 reduce(0, (acc, val) => (acc .. val), '')", 'E1252:')
+  " call assert_fails("vim9 reduce({}, (acc, val) => (acc .. val), '')", 'E1252:')
+  " call assert_fails("vim9 reduce(0.1, (acc, val) => (acc .. val), '')", 'E1252:')
+  " call assert_fails("vim9 reduce(function('tr'), (acc, val) => (acc .. val), '')", 'E1252:')
+  call assert_fails("call reduce('', { acc, val -> acc + val }, 1)", 'E1253:')
+  call assert_fails("call reduce('', { acc, val -> acc + val }, {})", 'E1253:')
+  call assert_fails("call reduce('', { acc, val -> acc + val }, 0.1)", 'E1253:')
+  call assert_fails("call reduce('', { acc, val -> acc + val }, function('tr'))", 'E1253:')
+
   let g:lut = [1, 2, 3, 4]
   func EvilRemove()
     call remove(g:lut, 1)