eval/typval: Add tv_dict_add_allocated_str() function

src/nvim/eval/typval.c

@@ -1386,12 +1386,33 @@ int tv_dict_add_str(dict_T *const d,
                     const char *const key, const size_t key_len,
                     const char *const val)
   FUNC_ATTR_NONNULL_ALL
+{
+  return tv_dict_add_allocated_str(d, key, key_len, xstrdup(val));
+}
+
+/// Add a string entry to dictionary
+///
+/// Unlike tv_dict_add_str() saves val to the new dictionary item in place of
+/// creating a new copy.
+///
+/// @warning String will be freed even in case addition fails.
+///
+/// @param[out]  d  Dictionary to add entry to.
+/// @param[in]  key  Key to add.
+/// @param[in]  key_len  Key length.
+/// @param[in]  val  String to add.
+///
+/// @return OK in case of success, FAIL when key already exists.
+int tv_dict_add_allocated_str(dict_T *const d,
+                              const char *const key, const size_t key_len,
+                              char *const val)
+  FUNC_ATTR_NONNULL_ALL
 {
   dictitem_T *const item = tv_dict_item_alloc_len(key, key_len);
 
   item->di_tv.v_lock = VAR_UNLOCKED;
   item->di_tv.v_type = VAR_STRING;
-  item->di_tv.vval.v_string = (char_u *)xstrdup(val);
+  item->di_tv.vval.v_string = (char_u *)val;
   if (tv_dict_add(d, item) == FAIL) {
     tv_dict_item_free(item);
     return FAIL;

test/unit/eval/typval_spec.lua

@@ -1963,6 +1963,38 @@ describe('typval.c', function()
           alloc_log:check({})
         end)
       end)
+      describe('allocated_str()', function()
+        itp('works', function()
+          local d = dict({test=10})
+          eq({test=10}, dct2tbl(d))
+          alloc_log:clear()
+          local s1 = lib.xstrdup('TEST')
+          local s2 = lib.xstrdup('TEST')
+          local s3 = lib.xstrdup('TEST')
+          alloc_log:check({
+            a.str(s1, 'TEST'),
+            a.str(s2, 'TEST'),
+            a.str(s3, 'TEST'),
+          })
+          eq(OK, lib.tv_dict_add_allocated_str(d, 'testt', 3, s1))
+          local dis = dict_items(d)
+          alloc_log:check({
+            a.di(dis.tes, 'tes'),
+          })
+          eq({test=10, tes='TEST'}, dct2tbl(d))
+          eq(FAIL, check_emsg(function() return lib.tv_dict_add_allocated_str(d, 'testt', 3, s2) end,
+                              'E685: Internal error: hash_add()'))
+          alloc_log:clear()
+          lib.emsg_skip = lib.emsg_skip + 1
+          eq(FAIL, check_emsg(function() return lib.tv_dict_add_allocated_str(d, 'testt', 3, s3) end,
+                              nil))
+          lib.emsg_skip = lib.emsg_skip - 1
+          alloc_log:clear_tmp_allocs()
+          alloc_log:check({
+            a.freed(s3),
+          })
+        end)
+      end)
     end)
     describe('clear()', function()
       itp('works', function()