Loading a muon file in python creates unwanted output

[Roman Tolchenov]

ws = Load('MUSR15189') creates the data workspace and the grouping table named LoadChildWorkspace.

Loading the same file from the GUI creates only the data.

[Arturs Bekasovs]

LoadMuonNexus has two optional output workspace properties. In the algorithm code, these are returned only if their name is set to something. So it's fine when you run

ws = LoadMuonNexus("MUSR15189") 

Though the generic Load algorithm sets LoadChildWorkspace to all the unset output workspace properties (to make validator happy), even if the workspace is optional, which causes the described behaviour.

The problem could be solved by fixing Load algorithm to check if the WorkspaceProperty is optional first. I've tried that quickly and it seem to work, though I need somebody more senior to take a look at that.

[Arturs Bekasovs]

This doesn't happen if we run it from the dialog, because the dialog sets the workspace properties specifically to input value (which is "" if we leave them empty), after they were set to LoadChildWorkspace (which happens when the filename property is changed). Python caller doesn't do that, neither does C++ invocation of Load, which causes LoadChildWorkspaces to be created.

[Arturs Bekasovs]

Refs #9104. Don't set up optional output ws properties.

Changeset: 748abbddb496ee674f1878a9131ab06b5050f3c3

[Arturs Bekasovs]

Tester:

Somebody senior please, core stuff.

Please make sure you understand the implications behind the change (I've tried to explain my understanding in previous comments) and that the code update is reasonable and not dangerous. Obviously, system/unit tests should be passing.

Then verify that the additional workspaces are not created when loading Muon file both using Load from Python and load dialog.

[Arturs Bekasovs]

An issue related to this one: createChildAlgorithm also sets output workspaces to ChildAlgOutput no matter what their isOptional() status is.

[Arturs Bekasovs]

createChildAlgorithm case is more complicated than the Load one, as suggested by Martyn, so not touching it in this ticket.

Additionally, tests should be added for the Load to check that it is now behaving correctly when optional output workspaces

1. are requested
2. are not requested

[Arturs Bekasovs]

Refs #9104. Tests for new functionality

Changeset: 3d9e6c238dd550af4a3acef4075997fb92102f03

[Arturs Bekasovs]

Tester:

See comment:6.

Additionally, please verify the added tests.

[Martyn Gigg]

I think leaving createChildAlgorithm alone is the correct thing to do as it's a simple utility function that sets up the algorithm appropriately in 99% of circumstances. A caller is free to override what it has created anyway.

[Martyn Gigg]

The code change looks fine and I confirm that now in Python you only get the single output workspace if that was all you specified but you get the extra ones if you have requested them.

[Martyn Gigg]

Merge remote-tracking branch 'origin/feature/9104_load_option_output_ws'

Full changeset: ​eac5434cb5188934659e449ddcf95184b14d0d1d

[Stuart Campbell]

This ticket has been transferred to github issue ​9947