revamp the sbt plugin

[fommil]

The default sbt-scalafmt plugin is not fit for purpose: there is no configuration and it blindly formats everything (no concept of unmanaged sources, etc, etc, although this can all be worked around manually). These problems were addressed in neo-sbt-scalafmt but it is really slow.

Now that sbt 1.0 supports scala 2.12 there is no need for the classloader hacks in https://github.com/lucidsoftware/neo-sbt-scalafmt/blob/master/sbt-scalafmt/src/main/scala/com/lucidchart/sbt/scalafmt/ScalafmtCorePlugin.scala

The 1.0 plugin should depend on scalafmt-core directly, no coursier or CLI nonsense, and retain the following Settings / Tasks (which are scoped per project / config) from the neo plugin:

• scalafmt
• scalafmtOnCompile
• scalafmtConfig
• scalafmt:test but renamed to scalafmtCheck to avoid creating a config
• sbt:scalafmt but renamed to scalafmtSbt with a corresponding scalafmtSbtCheck. This should format *.sbt files (with the appropriate dialect) and the project/*.scala files.
• scalafmtOnly a new task, which could be easily automated from emacs/vim/etc which takes a single file and formats it. This is ideal for "format on save" hooks.

The first cut can skip all the caching and simply do a brute-force format.

[sjrd]

If you plan to base the source detection on unmanagedSources (which I approve), how do you suggest dealing with various configurations? I see two options:

• Either scalafmt and the other tasks are scoped per config (so it's actually compile:scalafmt), which makes it easy to depend on sources in (Compile, scalafmt) itself depending on unmanagedSourceDirectories in (Compile, scalafmt), but means I need to explicitly perform test:scalafmt to format my test suite,
• Or scalafmt and the other tasks are scoped in the Zero config, which means I only need scalafmt to format main/ and test/, but makes it unclear where to fetch the sources from. In particular, how to deal with the it: configuration, or worse, custom configurations?

[fommil]

Yup, first choice... compile:scalafmt etc. In my projects at work I create an alias fmt which formats all known configurations and I use format on compile so I never in reality need to run it (CI runs the fmtTest alias).

[olafurpg]

Very nice! I approve 👍 @leonardehrenfried may also be interested.

Some practicalities, com.geirsson:sbt-scalafmt is currently released for sbt 1.0 without using any classloading/coursier hacks. The plugin does very little however, it only exposes a scalafmt command that invokes the cli.

scalafmt/scalafmt-sbt/src/main/scala/org/scalafmt/sbt/ScalafmtPlugin.scala

Line 10 in 49815ab

Command.args("scalafmt", "run the scalafmt command line interface.") {

The build runs scripted tests on sbt 1.0 and a pre-release of the plugin is released on every merge to bintray. All that is missing is a more idiomatic sbt user experience :) I personally don't use sbt-scalafmt so I will leave it to you to decide how to manage configurations/unmanagedSources/...

[olafurpg]

btw, there may be some utilities in scalafmt-cli that are useful for the sbt plugin. We can move them to the core module or the sbt plugin can depend on the cli module, either way you prefer.

[leonardehrenfried]

I would be quite interested however currently I'm focusing my "speeding up sbt" open source work on trying to bring coursier into sbt itself: coursier/coursier#601 (comment)

I would still be happy to become the plugin's maintainer but cannot actually develop this upgrade myself.

[olafurpg]

Fixed in #1085 @fommil ?