Fix read_json category dtype

Author: taoufik07

pandas/io/json/_json.py

@@ -12,7 +12,7 @@
 from pandas._typing import JSONSerializable
 from pandas.errors import AbstractMethodError
 
-from pandas.core.dtypes.common import ensure_str, is_period_dtype
+from pandas.core.dtypes.common import ensure_str, is_period_dtype, is_categorical_dtype
 
 from pandas import DataFrame, MultiIndex, Series, isna, to_datetime
 from pandas.core.construction import create_series_with_explicit_dtype
@@ -892,7 +892,8 @@ def _try_convert_data(self, name, data, use_dtypes=True, convert_dates=True):
                 )
                 if dtype is not None:
                     try:
-                        dtype = np.dtype(dtype)
+                        if not is_categorical_dtype(dtype):
+                            dtype = np.dtype(dtype)
                         return data.astype(dtype), True
                     except (TypeError, ValueError):
                         return data, False

pandas/tests/io/json/test_pandas.py

@@ -1197,6 +1197,18 @@ def test_read_local_jsonl(self):
             expected = DataFrame([[1, 2], [1, 2]], columns=["a", "b"])
             tm.assert_frame_equal(result, expected)
 
+    def test_read_json_category_dtype(self):
+        json = (
+            '{"a": 0, "b": "A"}\n'
+            '{"a": 1, "b": "B"}\n'
+            '{"a": 2, "b": "B"}\n'
+            '{"a": 3, "b": "B"}\n'
+        )
+        json = StringIO(json)
+        result = read_json(json, lines=True, dtype={"a": "category"})
+        expected = DataFrame([[0, "foo"], [1, "bar"], [2, "foo"], [3, "bar"]])
+        tm.assert_frame_equal(result, expected)
+
     def test_read_jsonl_unicode_chars(self):
         # GH15132: non-ascii unicode characters
         # \u201d == RIGHT DOUBLE QUOTATION MARK