Simple api returns don't ignore optional properties

[Martyn Gigg]

The simple API wrappers in the new API are not checking whether a workspace is optional when trying to return it. The old API used to accept the output properties even if they didn’t get produced. Example

from mantid.api import *
from mantid.kernel import *

class OptionalWorkspace(PythonAlgorithm):
    def PyInit(self):
        self.declareProperty(MatrixWorkspaceProperty("RequiredWorkspace", "", Direction.Output))
        self.declareProperty(MatrixWorkspaceProperty("OptionalWorkspace", "", Direction.Output, PropertyMode.Optional))
 
    def PyExec(self):
        ws = WorkspaceFactory.create("Workspace2D", NVectors=1, YLength=1,XLength=1)
        ws.dataY(0)[0] = 5
        self.setProperty("RequiredWorkspace", ws)

        optionalstr = self.getPropertyValue("OptionalWorkspace")
        if optionalstr != "":
          ws = WorkspaceFactory.create("Workspace2D", NVectors=1, YLength=1,XLength=1)
          ws.dataY(0)[0] = 10
          self.setProperty("OptionalWorkspace", ws)
          
        self.getLogger().notice("done!")

result = OptionalWorkspace(RequiredWorkspace="required", OptionalWorkspace="optional")

This should just return the required one as the even though the optional was specified the algorithm didn't create it but it was marked optional so that should be considered okay.

[Martyn Gigg]

Fix Python bug with optional workspace properties.

It now allows an optional output workspace to be specified within the input arguments but still not exist after the algorithm has been executed. Refs #7230

Changeset: 37e5a48a5c16501c7f679f3aed20f3ddc13dbd1b

[Martyn Gigg]

Branch: bugfix/7230_simpleapi_optional_workspace_retvals

Tester: The above test algorithm should allow you to check that the optional output can indeed be ignored.

[Russell Taylor]

My scripts work now...

[Stuart Campbell]

This ticket has been transferred to github issue ​8076