[SR-11513] Package Manager Reports Bogus “Cyclic Dependency”

[swift-ci]

Previous ID	SR-11513
Radar	rdar://problem/55665943
Original Reporter	SDGGiesbrecht (JIRA User)
Type	Bug

Environment

The same thing occurs on both macOS 10.14 (Mojave) and Ubuntu 18 (Bionic). The bug is completely new to Swift 5.1. Earlier versions of Swift handled this situation just fine.

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Package Manager | |Labels | Bug | |Assignee | None | |Priority | Medium | md5: 091f476a2b16b059d29fb51e98572f8a

Issue Description:

If the directory name of the package under development collides with the final path component of a dependency, the package manager refuses to do anything, falsely reporting a cyclic dependency.

This three‐line script triggers it using the package manager’s own demonstration packages:

git clone https://github.com/apple/example-package-deckofplayingcards example-package-fisheryates
cd example-package-fisheryates
swift build

And this is the resulting complaint:

error: the package example-package-fisheryates[[...]/example-package-fisheryates] depends on itself
error: cyclic dependency declaration found: DeckOfPlayingCards -> DeckOfPlayingCards

The first half of the error does not always appear.

With --enable-pubgrub-resolver the only output is “Illegal instruction: 4” instead.

[aciidgh]

This is used for the overriding behavior for path-based dependencies. Perhaps we can do something better here but PubGrub shouldn't crash at the very least.

[aciidgh]

@swift-ci create