vim-patch:8.2.2336: Vim9: not possible to extend dictionary with different type (#22425)

Problem:    Vim9: it is not possible to extend a dictionary with different
            item types.
Solution:   Add extendnew(). (closes vim/vim#7666)

https://github.com/vim/vim/commit/b0e6b513648db7035046613431a4aa9d71ef4653

Co-authored-by: Bram Moolenaar <Bram@vim.org>

5 files changed, 82 insertions, 14 deletions

diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 35f1b7cd6f..3ff4e47a45 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -138,6 +138,9 @@ expandcmd({string} [, {options}])
 				String	expand {string} like with `:edit`
 extend({expr1}, {expr2} [, {expr3}])
 				List/Dict insert items of {expr2} into {expr1}
+extendnew({expr1}, {expr2} [, {expr3}])
+				List/Dict like |extend()| but creates a new
+					List or Dictionary
 feedkeys({string} [, {mode}])	Number	add key sequence to typeahead buffer
 filereadable({file})		Number	|TRUE| if {file} is a readable file
 filewritable({file})		Number	|TRUE| if {file} is a writable file
@@ -2119,6 +2122,14 @@ extend({expr1}, {expr2} [, {expr3}])			*extend()*
 		Can also be used as a |method|: >
 			mylist->extend(otherlist)
 
+
+extendnew({expr1}, {expr2} [, {expr3}])			*extendnew()*
+		Like |extend()| but instead of adding items to {expr1} a new
+		List or Dictionary is created and returned.  {expr1} remains
+		unchanged.  Items can still be changed by {expr2}, if you
+		don't want that use |deepcopy()| first.
+
+
 feedkeys({string} [, {mode}])				*feedkeys()*
 		Characters in {string} are queued for processing as if they
 		come from a mapping or were typed by the user.
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 77b1795a57..0f2cfdd2ac 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -650,6 +650,7 @@ List manipulation:					*list-functions*
 	insert()		insert an item somewhere in a List
 	add()			append an item to a List
 	extend()		append a List to a List
+	extendnew()		make a new List and append items
 	remove()		remove one or more items from a List
 	copy()			make a shallow copy of a List
 	deepcopy()		make a full copy of a List
@@ -681,6 +682,7 @@ Dictionary manipulation:				*dict-functions*
 	empty()			check if Dictionary is empty
 	remove()		remove an entry from a Dictionary
 	extend()		add entries from one Dictionary to another
+	extendnew()		make a new Dictionary and append items
 	filter()		remove selected entries from a Dictionary
 	map()			change each Dictionary entry
 	keys()			get List of Dictionary keys
diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index 0c6912a702..a476e20339 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -120,6 +120,7 @@ return {
     expand={args={1, 3}, base=1},
     expandcmd={args={1, 2}, base=1},
     extend={args={2, 3}, base=1},
+    extendnew={args={2, 3}, base=1},
     feedkeys={args={1, 2}, base=1},
     file_readable={args=1, base=1, func='f_filereadable'},  -- obsolete
     filereadable={args=1, base=1, fast=true},
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 13d8f52768..1baf96e281 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -1929,18 +1929,22 @@ static void f_flattennew(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   flatten_common(argvars, rettv, true);
 }
 
-/// "extend(list, list [, idx])" function
-/// "extend(dict, dict [, action])" function
-static void f_extend(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+/// "extend()" or "extendnew()" function.  "is_new" is true for extendnew().
+static void extend(typval_T *argvars, typval_T *rettv, char *arg_errmsg, bool is_new)
 {
-  const char *const arg_errmsg = N_("extend() argument");
-
   if (argvars[0].v_type == VAR_LIST && argvars[1].v_type == VAR_LIST) {
     bool error = false;
 
-    list_T *const l1 = argvars[0].vval.v_list;
+    list_T *l1 = argvars[0].vval.v_list;
     list_T *const l2 = argvars[1].vval.v_list;
-    if (!value_check_lock(tv_list_locked(l1), arg_errmsg, TV_TRANSLATE)) {
+    if (is_new || !value_check_lock(tv_list_locked(l1), arg_errmsg, TV_TRANSLATE)) {
+      if (is_new) {
+        l1 = tv_list_copy(NULL, l1, false, get_copyID());
+        if (l1 == NULL) {
+          return;
+        }
+      }
+
       listitem_T *item;
       if (argvars[2].v_type != VAR_UNKNOWN) {
         long before = (long)tv_get_number_chk(&argvars[2], &error);
@@ -1962,11 +1966,18 @@ static void f_extend(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
       }
       tv_list_extend(l1, l2, item);
 
-      tv_copy(&argvars[0], rettv);
+      if (is_new) {
+        *rettv = (typval_T){
+          .v_type = VAR_LIST,
+          .v_lock = VAR_UNLOCKED,
+          .vval.v_list = l1,
+        };
+      } else {
+        tv_copy(&argvars[0], rettv);
+      }
     }
-  } else if (argvars[0].v_type == VAR_DICT && argvars[1].v_type ==
-             VAR_DICT) {
-    dict_T *const d1 = argvars[0].vval.v_dict;
+  } else if (argvars[0].v_type == VAR_DICT && argvars[1].v_type == VAR_DICT) {
+    dict_T *d1 = argvars[0].vval.v_dict;
     dict_T *const d2 = argvars[1].vval.v_dict;
     if (d1 == NULL) {
       const bool locked = value_check_lock(VAR_FIXED, arg_errmsg, TV_TRANSLATE);
@@ -1975,7 +1986,14 @@ static void f_extend(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     } else if (d2 == NULL) {
       // Do nothing
       tv_copy(&argvars[0], rettv);
-    } else if (!value_check_lock(d1->dv_lock, arg_errmsg, TV_TRANSLATE)) {
+    } else if (is_new || !value_check_lock(d1->dv_lock, arg_errmsg, TV_TRANSLATE)) {
+      if (is_new) {
+        d1 = tv_dict_copy(NULL, d1, false, get_copyID());
+        if (d1 == NULL) {
+          return;
+        }
+      }
+
       const char *action = "force";
       // Check the third argument.
       if (argvars[2].v_type != VAR_UNKNOWN) {
@@ -1999,13 +2017,37 @@ static void f_extend(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 
       tv_dict_extend(d1, d2, action);
 
-      tv_copy(&argvars[0], rettv);
+      if (is_new) {
+        *rettv = (typval_T){
+          .v_type = VAR_DICT,
+          .v_lock = VAR_UNLOCKED,
+          .vval.v_dict = d1,
+        };
+      } else {
+        tv_copy(&argvars[0], rettv);
+      }
     }
   } else {
-    semsg(_(e_listdictarg), "extend()");
+    semsg(_(e_listdictarg), is_new ? "extendnew()" : "extend()");
   }
 }
 
+/// "extend(list, list [, idx])" function
+/// "extend(dict, dict [, action])" function
+static void f_extend(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  char *errmsg = N_("extend() argument");
+  extend(argvars, rettv, errmsg, false);
+}
+
+/// "extendnew(list, list [, idx])" function
+/// "extendnew(dict, dict [, action])" function
+static void f_extendnew(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+{
+  char *errmsg = N_("extendnew() argument");
+  extend(argvars, rettv, errmsg, true);
+}
+
 /// "feedkeys()" function
 static void f_feedkeys(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
diff --git a/src/nvim/testdir/test_listdict.vim b/src/nvim/testdir/test_listdict.vim
index 37c1ee8307..fa22bad0cb 100644
--- a/src/nvim/testdir/test_listdict.vim
+++ b/src/nvim/testdir/test_listdict.vim
@@ -881,6 +881,18 @@ func Test_listdict_extend()
   call assert_equal([1, 5, 7, 1, 5, 7], l)
 endfunc
 
+func Test_listdict_extendnew()
+  " Test extendnew() with lists
+  let l = [1, 2, 3]
+  call assert_equal([1, 2, 3, 4, 5], extendnew(l, [4, 5]))
+  call assert_equal([1, 2, 3], l)
+
+  " Test extend() with dictionaries.
+  let d = {'a': {'b': 'B'}}
+  call assert_equal({'a': {'b': 'B'}, 'c': 'cc'}, extendnew(d, {'c': 'cc'}))
+  call assert_equal({'a': {'b': 'B'}}, d)
+endfunc
+
 func s:check_scope_dict(x, fixed)
   func s:gen_cmd(cmd, x)
     return substitute(a:cmd, '\<x\ze:', a:x, 'g')