Fix bug when changing the number of bins on a histogram with modified/deleted data

glue/core/application_base.py

@@ -93,6 +93,9 @@ def new_data_viewer(self, viewer_class, data=None, state=None):
         self.add_widget(c)
         return c
 
+    def add_widget(self, viewer):
+        pass
+
     @catch_error("Failed to save session")
     def save_session(self, path, include_data=False, absolute_paths=True):
         """

glue/core/state_objects.py

@@ -9,9 +9,10 @@
                                 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']
+           'StateAttributeLimitsHelper', 'StateAttributeSingleValueHelper', 'StateAttributeHistogramHelper']
 
 
 @saver(CallbackList)
@@ -428,9 +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):
-        for att in self._cache:
-            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:

glue/viewers/histogram/tests/test_state.py

@@ -0,0 +1,59 @@
+from glue.viewers.common.viewer import Viewer
+from glue.viewers.histogram.state import HistogramViewerState
+from glue.core.application_base import Application
+from glue.core.data import Data
+
+
+class TestHistogramViewer(Viewer):
+    _state_cls = HistogramViewerState
+
+
+def test_remove_data_collection():
+
+    # Regression test for a bug that caused an IncompatibleAttribute
+    # error when updating the number of bins in a histogram after
+    # removing a dataset from the DataCollection (this was due to
+    # a caching issue)
+
+    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.hist_n_bin = 30
+
+    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