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Posts tagged: vim

Doing stuff when files change

There’s a common pattern in development tools to help with rapid feedback: you run a long-lived process that does a certain task. At the same time, it watches the filesystem and restarts or re-runs that task whenever a file that you’re monitoring changes.

This is an extremely useful tool for rapid feedback (which is why we’ve integrated nodemon into our Conductance app server), but is not very flexible - most tools are integrated into a web framework or other environment, and can’t easily be used outside of it. There are a few generic tools to do this kind of thing - I personally use watchdog a lot, but it’s sucky in various ways:

  • Configuring it to watch the right file types is hard
  • Configuring it to ignore “junk” files is hard, leading to infinite feedback loops if you get it wrong
  • It sees about 6 events from a single “save file” action, and then insists on running my build script 6 times in a row
  • It takes a bash string, rather than a list of arguments - so you have to deal with double-escaping all your special characters

And yet for all of those issues, I haven’t found a better tool that does what I need.

My build workflow

Lately, I’ve been making heavy use of my relatively-new build system, gup. It’s a bit like make, but way better in my humble-and-totally-biased-opinion. But going to a terminal window and typing up, enter (or the wrist-saving alternative crtl-p, ctrl-m) to rebuild things is tedious. But there’s no way I’m going to implement yet another watch-the-filesystem-and-then-re-run-something gup-specific tool, at least not until the lazy alternatives have been exhausted.

Obviously, my workflow isn’t just up, enter. It’s (frequently):

  • save file in vim
  • go to terminal
  • press up, enter
  • go to browser
  • refresh

And you know what? Monitoring every file is kind of dumb for this workflow. I don’t have gremlins running around changing files in my working tree at random (I hope), I almost always want to reload in response to me changing a file (with vim, of course). So why not just cooperate?

The simple fix

So I’ve written a stupid-dumb vim plugin, and a stupid-dumb python script. The vim plugin touches a file in $XDG_USER_DIR whenever vim saves a file. And then the script monitors just this file, and does whatever you told it to do each time the file is modified. The script automatically communicates with vim to enable / disable the plugin as needed, so it has no overhead when you’re not using it.

It’s called vim-watch, and I just gave you the link.

Addendum: restarting servers

While writing this post, I was a little disappointed that it still doesn’t quite replace tools that automatically restart a server when something changes, because it expects to run a build-style command that exits when it’s done - but servers run forever. Some unix daemons (like apache) restart themselves when you send them a HUP signal, but that’s not so common in app servers. So now huppy exists, too.

It’s a tiny utility that’ll run whatever long-lived process you tell it to, and when it receives a HUP signal it’ll kill that process (with SIGINT) if it’s still running, then restart it. It seems surprising that this didn’t exist before (maybe my google-fu is failing me) but on the other hand it’s less than 60 lines of code - hardly an expensive wheel to reinvent.

You can use it like:

$ # step 1: start your server
$ huppy run-my-server

$ # step 2: use vim-watch to reload the server on changes
$ vim-watch killall -HUP huppy

$ # Or, if you need to rebuild stuff before restarting the server,
$ vim-watch bash -c 'gup && killall -HUP huppy'

New GVim Icon

The official gvim icon (left) is showing its age. The palette seems to be from the days of 256color, there is no anti-aliasing to speak of in many variants, and it’s just generally bland. I have found a few more modern variants, most notably the tango version, but none of them looked terribly great to me.

So I set out to create a more modern rendering of the classic logo. I exchanged the round serifs for a round diamond, added some psuedo-3d shading, gradients and shadows. All in all I’m quite pleased with how it’s turned out: 128px / svg

If you’d like to use this for gvim, you should do something like this1:

mkdir -p ~/.icons
cd ~/.icons
wget http://gfxmonk.net/misc/gvim-icon-gfxmonk.tgz
tar zxf gvim-icon-gfxmonk.tgz
rm gvim-icon-gfxmonk.tgz

Then go to your system’s theme selector and pick the “gfxmonk” icon theme.

If all the other (non-gvim) icons have now reverted to the system default and you didn’t want that, you will need to edit ~/.icons/gfxmonk/index.theme and set the inherits value to the name of your preferred icon set2.

Note: the svg icon may need the norasi font installed to display properly.

  1. These instructions have been tested to work on fedora, but I fear other distros may have wildly different mechanisms for overriding icons.

  2. Forgive me if there is a better way for packaging/installing icons, this is my first attempt.

Background Make for GVim

I haven’t used vim’s :make command much, mostly because I don’t often use compiled languages, and setting :errorformat correctly for nonstandard programs is a dark, dark art.

Recently I got :make and :errorformat working well enough with sbt, so the only remaining problem is that vim completely locks up while the make task is going. That really sucks, as sbt can take a good 20 seconds to even just compile and install an android app.

Enter background-make (for GVim only, sorry terminal freaks). It’s not perfect, but for non-pathological makeprg settings it seems to work very reliably. It adds a :Make command that does exactly what :make does, except it does it in the background.

And it tries its very best to not disrupt you - by default, it’ll send a system notification the moment that make finishes. But it will then wait until you are in either insert or normal mode, at which point it’ll take the opportunity to pop up the error window and restore your cursor position / mode. (It has to wait for normal or insert mode because these are the only ones I can figure out how to restore ;))

It’s implemented by firing off a background make process with the current vim instance’s v:servername so that it knows where to send the results (thus the GVim requirement). Once complete, it uses --remote-send to tell the originating vim instance to open the now-complete errorfile. Oh, and it also requires a python-enabled vim, because vimscript makes me wince.