Temporary editor files trigger a server rebuild

[Profpatsch]

Emacs creates so-called lock files on edit, which are files starting with .#, e.g. .#Main.purs.
This causes server to trigger a rebuild on every edit.

I am torn on what the correct solution to this problem is:

• notabug
  • users will have to manage their filechanges and adjust their editors accordingly
• a fixed list of watch exceptions in pulp:
  • will have to be added for all editors on bug reports
  • introduces “magic” that might drive users with special use-cases crazy
• an option to ignore certain files
  • complicates the interface
  • users need to identify all files they don’t like to trigger a rebuild
  • manual work
• a combination of the last two
• parse .gitignore and use that
  • pulp only seems to support git at the moment, so no code for e.g. mercurial necessary
  • might induce lots of overhead (or adhoc parsing)

A verbose option that displays all file changes should be added anyways (for easy debugging).

[hdgarrood]

I think I like the .gitignore option the best, provided that my memory serves correctly and the glob patterns it uses are not particularly difficult to parse and match with. I think we'd only need to provide functions parse :: String -> Maybe Pattern and match :: Pattern -> String -> Boolean to match one file path at a time. I'm also keen on having --verbose do that (see also #31, which is slightly different, but I'd like to have a --verbose option do both of these things).

[Profpatsch]

The pattern format has a description here: https://git-scm.com/docs/gitignore#_pattern_format
One should refer to the git source code though when implementing.

There’s also hundreds of npm packages, probably of wildly varying quality: https://www.npmjs.com/search?q=gitignore

[Profpatsch]

It looks like https://github.com/kaelzhang/node-ignore is a good implementation that is specific to .gitignore syntax and doesn’t have any dependencies.

Most similar packages seem to depend on minimatch (which has a very similar syntax to .gitignore, but:

Pay attention that minimatch does not work in the gitignore way. To filter filenames according to .gitignore file, I recommend this module.

[hdgarrood]

Yep, I’m happy to add a dependency on that.

[Profpatsch]

I started work on this patch: master...Profpatsch:let-watch-honor-gitignore

[Profpatsch]

Okay, I feel a bit dumb now, because there’s also git check-ignore which does the same, but maps 1:1 with the actual git algorithm. I think it is best to wrap that.
Of course that means invoking git for every change (at most once every 100 milliseconds, because of the debounce function). I’d add a debug message if a file is ignored because it is ignored by git.