Better error checking and tests for xarray.set_options (pydata#1066)

Author: shoyer

xarray/core/options.py

@@ -2,7 +2,7 @@
 
 
 class set_options(object):
-    """Set global state within a controlled context
+    """Set options for xarray in a controlled context.
 
     Currently, the only supported option is ``display_width``, which has a
     default value of 80.
@@ -24,6 +24,10 @@ class set_options(object):
     >>> xr.set_options(display_width=80)
     """
     def __init__(self, **kwargs):
+        invalid_options = {k for k in kwargs if k not in OPTIONS}
+        if invalid_options:
+            raise ValueError('argument names %r are not in the set of valid '
+                             'options %r' % (invalid_options, set(OPTIONS)))
         self.old = OPTIONS.copy()
         OPTIONS.update(kwargs)
 

xarray/test/test_options.py

@@ -0,0 +1,19 @@
+import xarray
+import pytest
+
+from xarray.core.options import OPTIONS
+
+
+def test_invalid_option_raises():
+    with pytest.raises(ValueError):
+        xarray.set_options(not_a_valid_options=True)
+
+
+def test_nested_options():
+    original = OPTIONS['display_width']
+    with xarray.set_options(display_width=1):
+        assert OPTIONS['display_width'] == 1
+        with xarray.set_options(display_width=2):
+            assert OPTIONS['display_width'] == 2
+        assert OPTIONS['display_width'] == 1
+    assert OPTIONS['display_width'] == original