Monday, April 30, 2018

Don't Fear the Monad - T-shirts

Summary: I made some t-shirts.

For Christmas my brother-in-law got me the classic "Don't Fear the Monads" t-shirt, which comes complete with the Monad functions printed on it. Of course, while one adult geeky t-shirt is awesome, a child geeky t-shirt is even better, and a whole family full of them is best. I made some SVG designs for "Don't Fear the Functor" (for my son) and "Don't Fear the Applicative" (for my wife), available here (I followed the style of the Monad one, even if I disagree with some of the technical choices in the original). You can turn these into real t-shirts with the Cafe Press design your own feature. The result is pictured below.

Wednesday, April 18, 2018

Ghcid with colors

Summary: I've just released ghcid-0.7, which provides a much better user experience, including colors.

Ghcid is now over three years old, with 28 versions, but I'm particularly pleased with the improvements in the latest version. The focus has been on better defaults and a more polished user experience, some things you might spot:

Color output: GHC 8.2 added colored output, with important information highlighted. Previously Ghcid would explicitly disable that color. Now Ghcid embraces that color, turning the flag on for GHC versions that support it and ensuring any output munging is aware of the colors. It also enables colors in Hspec and colors the "All good" message green.

Color defaults: While enabling more color, it also provides --color=never to disable colors, and auto-detects when colors are likely to work well.

Error spans: Ghcid has always recommended that people turn on the -ferror-spans flag, but now it does it for you. For people using the VS Code addin that will provide a smoother experience out of the box.

Parallel compilation: Ghcid now passes -j to ghci, which I find speeds up compilation by about one third. Not a huge speedup, but still useful.

Tracking files: Ghcid now tracks both the .ghcid file (which you can use to specify the command line you want to use with ghcid) and .ghci file (which configures ghci). If either change it will cause Ghcid to restart, picking up the changes.

Absolute paths: The internals of Ghcid have been rewritten to always use absolute file paths, rather than relative paths. If your ghci wrapper changes directory (as I believe multi-project cabal new-repl does) Ghcid will continue to work.

Enabling IDE improvements: I have improved the integration features for editor plugins - you can now output a .json file with the parsed messages, including start/end position, and escape codes. There is a new --setup flag for sending initial messages to the underlying ghci. I haven't modified any of the IDE plugins to take advantage of these new features, but that's phase 2.

Ctrl-C and cleaning up processes: Ghcid is a continual fight to deal properly with Ctrl-C and close down all appropriate processes at the right time. In this release I've fought the battle in a few more corners, seemingly with some level of success.

Crazy extensions: GHC 8.4 is now able to deal with both RebindableSyntax and OverloadedStrings and still start ghci. I've modified Ghcid so it can also deal with this composition.

Together these changes make for a much more pleasant user experience.