laughedelic / scalafmt-probot

🤖Github bot for checking code formatting with scalafmt

Scalafmt probot 🤖

A GitHub App built with Probot and Scala.js that runs Scalafmt on your pull-requests and reports any problems with code formatting using GitHub Checks API.

🚧 WORK IN PROGRESS 🚧

This project is in active development, it's not ready for usage yet.

scalafmt-probot's Issues

Take into account excludeFilters/includeFilters

The bot parses .scalafmt.conf, but the check is run on the files contents, so the filters in project.excludeFilters should be applied out to the list of files to check. (also project.includeFilters?)

Actions

Here are some ideas for the possible actions:

• when there's no .scalafmt.conf, cancel the check and offer an action to add an empty config
• when the check fails, offer an action to commit fixed formatting
• fail-fast by default, but offer an action to run the full check with a detailed report (see #1)

I think that interactiveness is great, but I don't like that it forces the user to give write permissions to all repos where they install this app.

Check only changed files

Current simple implementation just lists all files in the repo (at a given commit) and checks their formatting. This may take a long time in big repos. So the plan is to check only the files changed in the PR (i.e. assuming that master stays well-formatted).

• https://developer.github.com/v3/repos/commits/#compare-two-commits
• one check suite/run may correspond to different PRs with different base references (not necessarily master)
• when the .scalafmt.conf is among changed files, we still need to (re)check all files

Fail-fast behaviour vs. detailed reports

On one hand Checks API provides some means to make detailed reports with comments on particular lines of sources. So when the formatting check fails, it could generate a diff and comment on the pieces of the mis-formatted code.

On the other hand I personally don't see much value in such detailed reports. I would prefer the check to fail on the first mis-formatted file and report immediately, so that the feedback would be quick. I think that in most cases you don't care what exactly was mis-formatted, you just forgot to do it and as soon as you got this reminder on GitHub, you can just run scalafmt locally (in whatever preferred way) and fix it.

It could be a configuration option, but I would like to avoid a bot-specific configuration and even if there was one, I want to choose a sensible default.