Change supertype calculation when combining scatters

[stxue1]

#5055

Changelog Entry

To be copied to the draft changelog by merger:

• Fixed a bug with conditional statements inside a WDL scatter

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[DailyDreaming]

This can be simplified... but I'm not sure that the logic still holds up? optional seems like it will be set to the previous typ in types, if True, and will remain True the entire loop thereafter.

Here's the simplification:

supertype = None
optional = False
for typ in types:
    if isinstance(typ, WDL.Type.Any):
        # ignore an Any type, as we represent a bottom type as Any. See https://miniwdl.readthedocs.io/en/latest/WDL.html#WDL.Type.Any
        # and https://github.com/openwdl/wdl/blob/e43e042104b728df1f1ad6e6145945d2b32331a6/SPEC.md?plain=1#L1484
        optional = optional or typ.optional
    else:
        if supertype is None:
            supertype = typ
            optional = optional or typ.optional
        else:
            # We have conflicting types
            raise RuntimeError(f"Cannot generate a supertype from conflicting types: {types}")

==>

supertype = None
optional = False
for typ in types:
    if isinstance(typ, WDL.Type.Any):
        # ignore an Any type, as we represent a bottom type as Any. See https://miniwdl.readthedocs.io/en/latest/WDL.html#WDL.Type.Any
        # and https://github.com/openwdl/wdl/blob/e43e042104b728df1f1ad6e6145945d2b32331a6/SPEC.md?plain=1#L1484
        optional = optional or typ.optional
    elif supertype is None:
        supertype = typ
        optional = optional or typ.optional
    else:
        # We have conflicting types
        raise RuntimeError(f"Cannot generate a supertype from conflicting types: {types}")

==>

supertype = None
optional = False
for typ in types:
    optional = optional or typ.optional
    if supertype is None and not isinstance(typ, WDL.Type.Any):
        supertype = typ
    elif not isinstance(typ, WDL.Type.Any):
        # We have conflicting types
        raise RuntimeError(f"Cannot generate a supertype from conflicting types: {types}")

Is this still what it needs to do?

[stxue1]

I think this should be functionally similar, I can adjust the comment to give some clarification about the Any type as that is pretty important to keep

[stxue1]

This will actually break when the types list has multiple types in them, so I'll keep it as is

[adamnovak]

I think @DailyDreaming is right that we could factor out this line from the conditional.