[SPARK-48414][PYTHON] Fix breaking change in python's fromJson

### What changes were proposed in this pull request?

Fix breaking change in `fromJson` method by having default param values.

### Why are the changes needed?

In order to not break clients that don't care about collations.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Existing UTs.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes apache#46737 from stefankandic/fromJsonBreakingChange.

Authored-by: Stefan Kandic <stefan.kandic@databricks.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>

python/pyspark/sql/tests/test_types.py

@@ -818,6 +818,38 @@ def test_schema_with_collations_on_non_string_types(self):
             PySparkTypeError, lambda: _parse_datatype_json_string(collations_in_nested_map_json)
         )
 
+    def test_array_type_from_json(self):
+        arrayWithoutCollations = ArrayType(StringType(), True)
+        arrayWithCollations = ArrayType(StringType("UNICODE"), True)
+        array_json = {"type": "array", "elementType": "string", "containsNull": True}
+        collationsMap = {"element": "UNICODE"}
+
+        self.assertEqual(arrayWithoutCollations, ArrayType.fromJson(array_json))
+        self.assertEqual(
+            arrayWithCollations,
+            ArrayType.fromJson(array_json, fieldPath="", collationsMap=collationsMap),
+        )
+        self.assertEqual(
+            arrayWithCollations, ArrayType.fromJson(array_json, collationsMap=collationsMap)
+        )
+
+    def test_map_type_from_json(self):
+        mapWithoutCollations = MapType(StringType(), StringType(), True)
+        mapWithCollations = MapType(StringType("UNICODE"), StringType("UNICODE"), True)
+        map_json = {
+            "type": "map",
+            "keyType": "string",
+            "valueType": "string",
+            "valueContainsNull": True,
+        }
+        collationsMap = {"key": "UNICODE", "value": "UNICODE"}
+
+        self.assertEqual(mapWithoutCollations, MapType.fromJson(map_json))
+        self.assertEqual(
+            mapWithCollations, MapType.fromJson(map_json, fieldPath="", collationsMap=collationsMap)
+        )
+        self.assertEqual(mapWithCollations, MapType.fromJson(map_json, collationsMap=collationsMap))
+
     def test_schema_with_bad_collations_provider(self):
         from pyspark.sql.types import _parse_datatype_json_string, _COLLATIONS_METADATA_KEY
 

python/pyspark/sql/types.py

@@ -762,11 +762,13 @@ def jsonValue(self) -> Dict[str, Any]:
     def fromJson(
         cls,
         json: Dict[str, Any],
-        fieldPath: str,
-        collationsMap: Optional[Dict[str, str]],
+        fieldPath: str = "",
+        collationsMap: Optional[Dict[str, str]] = None,
     ) -> "ArrayType":
         elementType = _parse_datatype_json_value(
-            json["elementType"], fieldPath + ".element", collationsMap
+            json["elementType"],
+            "element" if fieldPath == "" else fieldPath + ".element",
+            collationsMap,
         )
         return ArrayType(elementType, json["containsNull"])
 
@@ -902,12 +904,14 @@ def jsonValue(self) -> Dict[str, Any]:
     def fromJson(
         cls,
         json: Dict[str, Any],
-        fieldPath: str,
-        collationsMap: Optional[Dict[str, str]],
+        fieldPath: str = "",
+        collationsMap: Optional[Dict[str, str]] = None,
     ) -> "MapType":
-        keyType = _parse_datatype_json_value(json["keyType"], fieldPath + ".key", collationsMap)
+        keyType = _parse_datatype_json_value(
+            json["keyType"], "key" if fieldPath == "" else fieldPath + ".key", collationsMap
+        )
         valueType = _parse_datatype_json_value(
-            json["valueType"], fieldPath + ".value", collationsMap
+            json["valueType"], "value" if fieldPath == "" else fieldPath + ".value", collationsMap
         )
         return MapType(
             keyType,