Add numpy encoder class for json.dumps and add test

Author: ericpre

zarr/tests/test_creation.py

@@ -540,3 +540,8 @@ def test_create_read_only():
     assert z.read_only
     with pytest.raises(PermissionError):
         z[:] = 42
+
+
+def test_json_dumps_chunks_numpy_dtype():
+    z = zeros((10,), chunks=(np.int64(2),))
+    assert np.all(z[...] == 0)

zarr/tests/test_util.py

@@ -4,8 +4,9 @@
 import numpy as np
 import pytest
 
-from zarr.util import (all_equal, flatten, guess_chunks, human_readable_size, info_html_report,
-                       info_text_report, is_total_slice, normalize_chunks,
+from zarr.util import (all_equal, flatten, guess_chunks, human_readable_size,
+                       info_html_report, info_text_report, is_total_slice,
+                       json_dumps, normalize_chunks,
                        normalize_dimension_separator,
                        normalize_fill_value, normalize_order,
                        normalize_resize_args, normalize_shape, retry_call,
@@ -238,3 +239,7 @@ def test_all_equal():
     # all_equal(None, *) always returns False
     assert not all_equal(None, np.array([None, None]))
     assert not all_equal(None, np.array([None, 10]))
+
+
+def test_json_dumps_numpy_dtype():
+    assert json_dumps(np.int64(0)) == json_dumps(0)

zarr/util.py

@@ -33,10 +33,23 @@ def flatten(arg: Iterable) -> Iterable:
 }
 
 
+class NumpyEncoder(json.JSONEncoder):
+
+    def default(self, o):
+        # See https://github.com/python/cpython/blob/e0ec08dc49f8e6f94a735bc9946ef7a3fd898a44/Lib/json/encoder.py#L160
+        if isinstance(o, np.integer):
+            return int(o)
+        if isinstance(o, np.floating):
+            return float(o)
+        if isinstance(o, np.ndarray):
+            return o.tolist()
+        return json.JSONEncoder.default(self, o)
+
+
 def json_dumps(o: Any) -> bytes:
     """Write JSON in a consistent, human-readable way."""
     return json.dumps(o, indent=4, sort_keys=True, ensure_ascii=True,
-                      separators=(',', ': ')).encode('ascii')
+                      separators=(',', ': '), cls=NumpyEncoder).encode('ascii')
 
 
 def json_loads(s: str) -> Dict[str, Any]: