Merge pull request #316 from mantidproject/11025_plotSlice_crashes_on…

…_peaks_ws

plotSlice on wrong workspace types: prevent crash and give informative error message

Code/Mantid/MantidPlot/pymantidplot/__init__.py

@@ -670,6 +670,8 @@ def plotSlice(source, label="", xydim=None, slicepoint=None,
         SliceViewer, e.g. setting the view and slice point.
     """
     workspace_names = getWorkspaceNames(source)
+    __checkPlotSliceWorkspaces(workspace_names)
+
     try:
         import mantidqtpython
     except:
@@ -1032,4 +1034,37 @@ def __checkPlotMDWorkspaces(workspace_names):
         if not isinstance(mantid.api.mtd[name], mantid.api.IMDWorkspace):
             raise ValueError("Workspace '%s' is not an IMDWorkspace" % name)
 
+
+def __checkPlotSliceWorkspaces(ws_names):
+    """Checks that a list of workspaces is valid as input to plotSlice.
+    That means that the list should not be empty, all the workspaces
+    given must be present in the analysis data service, and all of
+    them must be MDworkspace. If any of these conditions is not met,
+    it raises an exception with specific error message.
+
+    Throws Python-level exceptions (ValueError) if the list is empty
+    or any of the spaces don't exist or are not of IMDWorkspace type.
+
+    Args:
+        ws_names: list of names of workspace(s)
+
+    Returns:
+        Nothing, just throws exceptions in case of error/inconsistent input
+
+    """
+    if len(ws_names) == 0:
+        raise ValueError("No workspace name(s) given. You need to specify at least one.")
+    for name in ws_names:
+        if not mantid.api.mtd.doesExist(name):
+            raise ValueError("Workspace '%s' does not exist in the workspace list" % name)
+
+        if not isinstance(mantid.api.mtd[name], mantid.api.IMDWorkspace):
+            if isinstance(mantid.api.mtd[name], mantid.api.IPeaksWorkspace):
+                raise ValueError("'%s' is not an IMDWorkspace as expected, but an "
+                                 "IPeaksWorkspace instead. Hint: if you want to overlay "
+                                 "peaks and use the Peaks Viewer, maybe "
+                                 "setPeaksWorkspaces is what you need?" % name)
+            else:
+                raise ValueError("%s is not an IMDWorkspace as expected." % name)
+
 #-----------------------------------------------------------------------------

Code/Mantid/MantidQt/SliceViewer/src/LineViewer.cpp

@@ -656,6 +656,8 @@ bool LineViewer::getFixedBinWidthMode() const
  * @param ws :: IMDWorkspace */
 void LineViewer::setWorkspace(Mantid::API::IMDWorkspace_sptr ws)
 {
+  if(!ws)
+    throw std::runtime_error("LineViewer::setWorkspace(): Invalid workspace.");
   m_ws = ws;
   m_thickness = VMD(ws->getNumDims());
   createDimensionWidgets();