Tuesday, April 19, 2016

New Shake with better wildcard patterns

Summary: The new version of Shake supports ** patterns for directory wildcards.

I've just released Shake 0.15.6. Don't be mislead by the 0.0.1 increment of the release, it's got over 50 entries in the changelog since the last release. There are quite a few bug fixes, documentation improvements and optimisations.

One of the most user visible features is the new wildcard patterns. In the previous version Shake supported // for matching any number of directories and * for matching within a path component, so to match all C source files in src you could write:


In the new version of Shake you can also write:


The // patterns remain supported, but I intend to encourage use of ** in new code if these patterns don't end up having any unforeseen problems. The advantages of the patterns in the new version are:

  • The ** patterns seem to be the defacto standard nowadays, being used by rsync, Ant, Gradle, Jenkins etc.
  • People would often write "src" </> "//*.c", which gives the unexpected result of //*.c. With ** you aren't overloading directories at the same time so everything works out as expected.
  • ** patterns only match relative files, not absolute ones, which is what you usually want in a build system. If you want to match absolute files use */**.
  • The semantics of patterns were a bit confusing for things like /// - I've now given them precise semantics, but ** avoids this confusion.
  • I've optimised the pattern matching for both flavours, so there is more precomputation and less backtracking (in practice I don't think that makes any difference).
  • I've optimised directory traversal using a file pattern, so it doesn't list directories that can't possibly match, which gives a significant speedup.

For this release I've also improved the website at shakebuild.com with more documentation - hopefully it is useful.


Noah said...

By semantic versioning, shouldn't this new feature deserve a 0.1 increment?

Neil Mitchell said...

Noah: In a very technical sense, yes. However, I decided it wasn't strictly necessary because the previous syntax didn't mean anything and there were no API changes. In many senses it just makes the API more permissive. I agree it's definitely a judgement call, and I asked a couple of heavy Shake users before making that decision.