add transition from reading key to reading quoted key when double quotes are found

src/Functions/keyvaluepair/impl/StateHandlerImpl.h

@@ -106,6 +106,11 @@ public:
             {
                 return {next_pos, State::WAITING_KEY};
             }
+            else if (isQuotingCharacter(*p))
+            {
+                // +1 to skip quoting character
+                return {next_pos, State::READING_QUOTED_KEY};
+            }
 
             pos = next_pos;
         }

tests/queries/0_stateless/02499_extract_key_value_pairs_multiple_input.reference

@@ -345,6 +345,18 @@ WITH
 SELECT
     x;
 {'argument1':'1','argument2':'2','char':'=','char2':'=','formula':'1+2=3','result':'3','string':'foo=bar'}
+-- https://github.com/ClickHouse/ClickHouse/issues/56357
+WITH
+    extractKeyValuePairs('{"a":"1", "b":"2"}') as s_map,
+    CAST(
+        arrayMap(
+            (x) -> (x, s_map[x]), arraySort(mapKeys(s_map))
+        ),
+        'Map(String,String)'
+    ) AS x
+SELECT
+    x;
+{'a':'1','b':'2'}
 -- check str_to_map alias (it is case-insensitive)
 WITH
     sTr_tO_mAp('name:neymar, age:31 team:psg,nationality:brazil') AS s_map,

tests/queries/0_stateless/02499_extract_key_value_pairs_multiple_input.sql

@@ -481,6 +481,18 @@ WITH
 SELECT
     x;
 
+-- https://github.com/ClickHouse/ClickHouse/issues/56357
+WITH
+    extractKeyValuePairs('{"a":"1", "b":"2"}') as s_map,
+    CAST(
+        arrayMap(
+            (x) -> (x, s_map[x]), arraySort(mapKeys(s_map))
+        ),
+        'Map(String,String)'
+    ) AS x
+SELECT
+    x;
+
 -- check str_to_map alias (it is case-insensitive)
 WITH
     sTr_tO_mAp('name:neymar, age:31 team:psg,nationality:brazil') AS s_map,