Change default format in array editor to ''

Before, the default format in the array editor for non-numeric arrays
was set to 's'. This meant that ArrayModel.data() returned a value of
type numpy.str_ for string arrays instead of a value of type str. The
consequence was that the contents of the array were not shown. Changing
the default format to '' fixes this.

Also add a regression test.

spyder/plugins/variableexplorer/widgets/arrayeditor.py

@@ -71,7 +71,7 @@ class ArrayEditorWidgets:
     ToolbarStretcher = 'toolbar_stretcher'
 
 
-# Note: string and unicode data types will be formatted with 's' (see below)
+# Note: string and unicode data types will be formatted with '' (see below)
 SUPPORTED_FORMATS = {
     'single': '.6g',
     'double': '.6g',
@@ -657,7 +657,10 @@ def __init__(self, parent, data, readonly=False):
             self.old_data_shape = self.data.shape
             self.data.shape = (1, 1)
 
-        format_spec = SUPPORTED_FORMATS.get(data.dtype.name, 's')
+        # Use '' as default format specifier, because 's' does not produce
+        # a `str` for arrays with strings, see spyder-ide/spyder#22466
+        format_spec = SUPPORTED_FORMATS.get(data.dtype.name, '')
+
         self.model = ArrayModel(self.data, format_spec=format_spec,
                                 readonly=readonly, parent=self)
         self.view = ArrayView(self, self.model, data.dtype, data.shape)

spyder/plugins/variableexplorer/widgets/tests/test_arrayeditor.py

@@ -115,6 +115,23 @@ def test_type_errors(setup_arrayeditor, qtbot):
     assert_array_equal(contents, np.ones(10))
 
 
+@pytest.mark.parametrize(
+    'data',
+    [np.array([['a', 'b'], ['c', 'd']])]
+)
+def test_string_array_data_is_str(setup_arrayeditor):
+    """
+    Verify that the displayed data of an array of strings is of type `str`.
+
+    Regression test for spyder-ide/spyder#22466.
+    """
+    dlg = setup_arrayeditor
+    idx = dlg.arraywidget.model.index(0, 0)
+    data = dlg.arraywidget.model.data(idx)
+    assert data == 'a'
+    assert type(data) is str
+
+
 @pytest.mark.skipif(not sys.platform.startswith('linux'),
                     reason="Only works on Linux")
 @pytest.mark.parametrize(