build(opentrons): add onchange watch to make format command

[iansolano]

Add onchange lib to conditionally watch files using make format watch=true command and invoke
prettier on changed file

overview

Added onchange library recommended by prettier https://github.com/prettier/prettier/blob/master/docs/watching-files.md.

Initially tried to implement using watchman but proved to be quite difficult / could potentially require additional implied dependencies. Onchange is nice because now it requires no additional setups for engineers to begin watching for changes and running prettier.

Curious about watchman issues / have other ideas? These were my findings:

• Attempted to run the task watchman-wait . -p '**/*.js' -m 0 | xargs prettier --write. -m 0 disables the max-limit, so the task can continue to run but unfortunately did not allow me to pipe the stdout into prettier.
• Watchman-wait docs: https://facebook.github.io/watchman/docs/watchman-wait.html
• Past watchman issues:
• watchman-wait does't work with xargs facebook/watchman#230 (this still is a prob on my machine)
• This gives some insight from the library author as to use cases: https://stackoverflow.com/questions/46881854/when-using-watchmans-watch-make-i-want-to-access-the-name-of-the-changed-files

review requests

Open to different implementation suggestions and there are way to make this work with watchman but the ones I could think of seem unnecessarily burdensome to do a simple task like this.

[codecov]

Codecov Report

Merging #4804 into edge will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             edge    #4804   +/-   ##
=======================================
  Coverage   57.91%   57.91%           
=======================================
  Files         956      956           
  Lines       26235    26235           
=======================================
  Hits        15194    15194           
  Misses      11041    11041

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[mcous]

automatic formatting ftw 👔

[mcous]

Thanks for humoring me and trying out watchman. I foolishly forgot how much it sucks. Looks like onchange is a quality package (and uses chokidar under the hood) so 👍

[iansolano]

Np. Yeah, watchman deep smh 💀🌚

[mcous]

Looks like it might be good to throw these formatted file patterns into an internal Makefile variable