Expand tests and fix bug

glue/core/state_objects.py

@@ -9,6 +9,7 @@
                                 HasCallbackProperties, CallbackList)
 from glue.core.state import saver, loader
 from glue.core.component_id import PixelComponentID
+from glue.core.exceptions import IncompatibleAttribute
 
 __all__ = ['State', 'StateAttributeCacheHelper',
            'StateAttributeLimitsHelper', 'StateAttributeSingleValueHelper', 'StateAttributeHistogramHelper']
@@ -192,6 +193,7 @@ def _update_attribute(self, *args):
             self.update_values(attribute=self.component_id, use_default_modifiers=True)
 
     def _update_values(self, **properties):
+
         if hasattr(self, '_in_set'):
             if self._in_set:
                 return
@@ -427,11 +429,16 @@ def __init__(self, state, attribute, random_subset=10000, max_n_bin=30,
             self._common_n_bin = None
 
     def _apply_common_n_bin(self):
-        print('_apply_common_n_bin')
-        for att in self._cache:
-            print('att', att.label, att.parent.label)
-            if not self.data.get_kind(att) == 'categorical':
-                self._cache[att]['n_bin'] = self._common_n_bin
+        for att in list(self._cache):
+            try:
+                if not self.data.get_kind(att) == 'categorical':
+                    self._cache[att]['n_bin'] = self._common_n_bin
+            except IncompatibleAttribute:
+                # This can indicate that a dataset has been removed from the
+                # data collection or that the attribute has changed to a
+                # new dataset that is not compatible with the previous one.
+                # In this case we should remove the entry
+                self._cache.pop(att)
 
     def _update_common_n_bin(self, common_n_bin):
         if common_n_bin:
@@ -445,8 +452,6 @@ def _update_common_n_bin(self, common_n_bin):
 
     def update_values(self, force=False, use_default_modifiers=False, **properties):
 
-        print('main update_values', properties)
-
         if not force and not any(prop in properties for prop in ('attribute', 'n_bin')) or self.data is None:
             self.set()
             return

glue/viewers/histogram/tests/test_state.py

@@ -31,3 +31,29 @@ def test_remove_data_collection():
     app.data_collection.remove(data1)
 
     viewer.state.hist_n_bin = 20
+
+
+def test_incompatible_datasets():
+
+    # Regression test for a bug that caused an IncompatibleAttribute
+    # error when changing the dataset used in the histogram viewer to one that
+    # is not linked to the first dataset.
+
+    data1 = Data(x=[1, 2, 3], label='data1')
+    data2 = Data(y=[1, 2, 3], label='data2')
+
+    app = Application()
+    app.data_collection.append(data1)
+    app.data_collection.append(data2)
+
+    viewer = app.new_data_viewer(TestHistogramViewer)
+    viewer.add_data(data1)
+    viewer.add_data(data2)
+
+    viewer.state.x_att = data1.id['x']
+
+    viewer.state.hist_n_bin = 30
+
+    viewer.state.x_att = data2.id['y']
+
+    viewer.state.hist_n_bin = 20