[vcpkg-tool] Cycle detected error message is unhelpful

[horenmar]

Is your feature request related to a problem? Please describe.
Today I messed up my vcpkg.json a bit when trying to make one feature dependent on another, and got this error message:

Error: Cycle detected during onnxruntime:x64-windows-pexlib-custom:
pexlib:x64-windows-pexlib-custom

This is not helpful to debugging the issue.

Proposed solution
Print out packages that are part of the detected cycle. This is relatively easy graph problem, if we do not want to spam too much output to the user in case of failure, we can add a check on the size of the cycle and if the cycle size is e.g. >10, print out something like

Error: Dependency cycle of size XYZ detected, omitting parts of the cycle
Cycle: A -> B -> C -> ... -> foo -> bar -> quux -> A

[autoantwort]

Can you post an example file?

[horenmar]

I finally got around doing this. I built a simple self-contained port set through overlay ports, and played around with different possible cycles.

With a graph root -> A -> B -> C -> B, the output with current (2022-02-03-457b0309cefb58fae0dcb2e4c06de9bd7582967f) version of vcpkg-tool is

Error: Cycle detected during b:x64-windows:
a:x64-windows
b:x64-windows
c:x64-windows

so it tells me which package went wrong, but how do I know that the issue is b -> c -> b? 🤷

This is a toy setup to play with