add specific tests

Author: jorisvandenbossche

pandas/core/arrays/masked.py

@@ -539,7 +539,7 @@ def to_numpy(
             with warnings.catch_warnings():
                 warnings.filterwarnings("ignore", category=RuntimeWarning)
                 data = self._data.astype(dtype, copy=copy)
-            if self._readonly and astype_is_view(self.dtype, dtype):
+            if self._readonly and not copy and astype_is_view(self.dtype, dtype):
                 data = data.view()
                 data.flags.writeable = False
         return data

pandas/tests/arrays/boolean/test_construction.py

@@ -323,3 +323,13 @@ def test_to_numpy_copy():
     result = arr.to_numpy(dtype=bool, copy=True)
     result[0] = False
     tm.assert_extension_array_equal(arr, pd.array([True, False, True], dtype="boolean"))
+
+
+def test_to_numpy_readonly():
+    arr = pd.array([True, False, True], dtype="boolean")
+    arr._readonly = True
+    result = arr.to_numpy(dtype=bool)
+    assert not result.flags.writeable
+
+    result = arr.to_numpy(dtype="int64")
+    assert result.flags.writeable

pandas/tests/arrays/floating/test_to_numpy.py

@@ -130,3 +130,26 @@ def test_to_numpy_copy():
     result = arr.to_numpy(dtype="float64", copy=True)
     result[0] = 10
     tm.assert_extension_array_equal(arr, pd.array([0.1, 0.2, 0.3], dtype="Float64"))
+
+
+def test_to_numpy_readonly():
+    arr = pd.array([0.1, 0.2, 0.3], dtype="Float64")
+    arr._readonly = True
+    result = arr.to_numpy(dtype="float64")
+    assert not result.flags.writeable
+
+    result = arr.to_numpy(dtype="float64", copy=True)
+    assert result.flags.writeable
+
+    result = arr.to_numpy(dtype="float32")
+    assert result.flags.writeable
+
+    result = arr.to_numpy(dtype="object")
+    assert result.flags.writeable
+
+
+def test_asarray_readonly():
+    arr = pd.array([0.1, 0.2, 0.3], dtype="Float64")
+    arr._readonly = True
+    result = np.asarray(arr, copy=False)
+    assert not result.flags.writeable

pandas/tests/arrays/integer/test_dtypes.py

@@ -276,6 +276,22 @@ def test_to_numpy_na_raises(dtype):
         a.to_numpy(dtype=dtype)
 
 
+def test_to_numpy_readonly():
+    arr = pd.array([0, 1], dtype="Int64")
+    arr._readonly = True
+    result = arr.to_numpy()
+    assert not result.flags.writeable
+
+    result = arr.to_numpy(dtype="int64", copy=True)
+    assert result.flags.writeable
+
+    result = arr.to_numpy(dtype="int32")
+    assert result.flags.writeable
+
+    result = arr.to_numpy(dtype="object")
+    assert result.flags.writeable
+
+
 def test_astype_str(using_infer_string):
     a = pd.array([1, 2, None], dtype="Int64")
 

pandas/tests/arrays/numpy_/test_numpy.py

@@ -155,6 +155,33 @@ def test_to_numpy():
     tm.assert_numpy_array_equal(result, expected)
 
 
+def test_to_numpy_readonly():
+    arr = NumpyExtensionArray(np.array([1, 2, 3]))
+    arr._readonly = True
+    result = arr.to_numpy()
+    assert not result.flags.writeable
+
+    result = arr.to_numpy(copy=True)
+    assert result.flags.writeable
+
+    result = arr.to_numpy(dtype="f8")
+    assert result.flags.writeable
+
+
+@pytest.mark.parametrize("dtype", [None, "int64"])
+def test_asarray_readonly(dtype):
+    arr = NumpyExtensionArray(np.array([1, 2, 3]))
+    arr._readonly = True
+    result = np.asarray(arr, dtype=dtype)
+    assert not result.flags.writeable
+
+    result = np.asarray(arr, dtype=dtype, copy=True)
+    assert result.flags.writeable
+
+    result = np.asarray(arr, dtype=dtype, copy=False)
+    assert not result.flags.writeable
+
+
 # ----------------------------------------------------------------------------
 # Setitem
 

pandas/tests/arrays/string_/test_string.py

@@ -753,6 +753,16 @@ def test_to_numpy_na_value(dtype, nulls_fixture):
     tm.assert_numpy_array_equal(result, expected)
 
 
+def test_to_numpy_readonly(dtype):
+    arr = pd.array(["a", pd.NA, "b"], dtype=dtype)
+    arr._readonly = True
+    result = arr.to_numpy()
+    if dtype.storage == "python":
+        assert not result.flags.writeable
+    else:
+        assert result.flags.writeable
+
+
 def test_isin(dtype, fixed_now_ts):
     s = pd.Series(["a", "b", None], dtype=dtype)
 

pandas/tests/arrays/test_datetimelike.py

@@ -1274,6 +1274,28 @@ def test_to_numpy_extra(arr):
     tm.assert_equal(arr, original)
 
 
+@pytest.mark.parametrize(
+    "arr",
+    [
+        pd.date_range("2000", periods=4)._values,
+        pd.timedelta_range("2000", periods=4)._values,
+    ],
+)
+def test_to_numpy_extra_readonly(arr):
+    arr[0] = NaT
+    original = arr.copy()
+    arr._readonly = True
+
+    result = arr.to_numpy(dtype=object)
+    assert result.flags.writeable
+
+    # numpy does not do zero-copy conversion from M8 to i8
+    result = arr.to_numpy(dtype="int64")
+    assert result.flags.writeable
+
+    tm.assert_equal(arr, original)
+
+
 @pytest.mark.parametrize("as_index", [True, False])
 @pytest.mark.parametrize(
     "values",