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.

Monday, April 11, 2016

GHCid 0.6 Released

Summary: I've released a new version of GHCid, which can interrupt running tests.

I've just released version 0.6.1 of GHCid. To a first approximation, ghcid opens ghci and runs :reload whenever your source code changes, formatting the output to fit a fixed height console. Unlike other Haskell development tools, ghcid is intended to be incredibly simple - it works when nothing else does. This new version features:

Much faster: Since version 0.5 GHCid passes -fno-code to ghci when it makes sense, which is about twice as fast.

Interruptible test commands: Since version 0.4 ghcid has supported a --test flag to pass a test command (e.g. :main) which is run whenever the code is warning free. As of version 0.6 that command will be interrupted if it needs to :reload, allowing long running tests and persistent "tests" - e.g. spawning web servers or GUIs. Thanks to Reid Draper for showing it was possible as part of his ordeal project and Luigy Leon for merging that with GHCid.

Stack integration: If you have a stack.yaml function and a .stack-work directory it will use stack commands to run your project. Thanks to the Stack Team, in particular Michael Sloan, for helping get through all the hoops and providing the necessary functionality in Stack.

More restart/reload flags: It's been possible for a while to pass --restart to restart ghci if certain files change (e.g. the .cabal file). Now there is a separate --reload flag to cause :reload instead of a full restart, and both flags can take directories instead of individual files.

Major relayering: For 0.6 I significantly refactored much of the GHCid code. There has always been an underlying Language.Haskell.Ghcid API, and GHCid was built on top. With the new version the underlying library has been given a significant refactoring, mostly so that interruptions are handled properly without race conditions and with a sane multithreading story. On top of that is a new Session layer, which provides a session abstraction - a ghci instance which tracks more state (e.g. which warnings have been emitted for already loaded files). Then the Ghcid module builds on top, with much less state management. By simplifying and clarifying the responsibility of each layer certain issues such as leaking old ghci processes and obscure race conditions disappeared.

I've been making use of many of these features in the Shake website generator, which I invoke with:

ghcid --test=":main debug" --reload=parts --reload=../docs

This project uses Stack, so relies on the new stack integration. It runs :main debug as the test suite, which generates the website whenever the code reloads. Furthermore, if any of the parts (template files) or docs (Markdown pages) change the website regenerates. I can now edit the website, and saving it automatically regenerates the web pages within a second.

Wednesday, April 06, 2016

Github Offline Issues with IssueSync

For a while I've been looking for something to download the GitHub issues for a project. I do a lot of development work on a train with no internet, so referring to the tickets offline is very useful. I've tried lot of tools, in a very wide variety of languages (Ruby, Python, Perl, Javascript, PHP) - but most of them don't seem to work - and the only one I did manage to get working only gave a curses UI.

Finally, I've found one that works - IssueSync. Installing it worked as described. Running it worked as described. I raised tickets for the author and they fixed them. I even sent a pull request and the author discussed and merged it. It downloads all your issues to Markdown files in an issues directory. I then "list" my issues using:

head -n1 -q issues/*.md | grep -v CLOSED

It's simple and works nicely.