tree 2a356de045da9ff17563c223b4bb1d7857a653f3
parent ff93b19e496513dd78be4b6bcee0f0105cc17d2b
author nharmata <nharmata@google.com> 1550593822 -0800
committer Copybara-Service <copybara-worker@google.com> 1550593936 -0800

Fix long-standing corner case with infinite symlink expansion detection. See the added unit tests for more details.

The approach is to have FileFunction consider the entire logical chain of paths encountered during realpath resolution, not just the physical symlink chain. In order to implement this, we have FileValue instances embed the full logical chain of paths encountered during their own real path resolution. This leads to a natural recursive algorithm.

In addition to the new code being less buggy, I hope it's also either to reason about since the algorithm is more natural. The added code comments should help as well.

Another cool thing is that the error message printed to the user on infinite symlink expansion is much more useful since it shows them the full chain of paths.

While there is a theoretical memory concern (consider a path like 'a/b/c/d/e/f/g' where 'a' is a symlink to 'a1/b/c/d/e/f/g', 'b' is a symlink to 'b1/c/d/e/f/g', etc), in practice there's no noticeable memory increase for many use cases.

RELNOTES: None
PiperOrigin-RevId: 234606705