Graph ambiguity given multiple rules with the same intermediate path

[Eric-Arellano]

We would expect this to work:

X -> Z
A -> X -> Z
B -> X -> Z

But, it fails due to multiple ways to compute await Get[Z](X).

Specifically, this is causing graph ambiguity:

StripSnapshotRequest -> SourceRootStrippedSources
StripSourcesFieldRequest -> StripSnapshotRequest -> SourceRootStrippedSources
LegacyStripTargetRequest -> StripSnapshotRequest -> SourceRootStrippedSources

Refer to https://pantsbuild.slack.com/archives/C0D7TNJHL/p1584460732313100.

--

This works as a workaround:

X -> Z
A -> X -> Z
B -> X -> Z -> M

where M is a new type.

[stuhood]

The example in the description doesn't quite make sense to me... it seems like that should work just fine, so grabbing out a failing testcase next time someone encounters this would be helpful.

But I expect that either way this relates to #7710.

[Eric-Arellano]

I believe this was fixed by the new graph algorithm.