Clippy is a Scala compiler plugin which enriches compilation errors with additional advices. Last few months brought some new cool features. The most important are:

Colored diffs in type mismatch errors

Type-driven development gets more and more popular and sophisticated. Libraries like Shapeless and techniques like free monads become widespread, making type mismatch errors frequent and challenging. Sometimes it takes a moment to see differences between actual and expected type, especially for long signatures. Try for yourself and spot where's the difference in following example:

Clippy 0.4.1 offers a new feature - diff highlighting:

This option is disabled by default, so that CI logs and other outputs which don't support ANSI colors won't get affected when you update to the newest version. To turn highlighting on, add "-P:clippy:colors=true" to your scalac options. See the docs for more details.

Local advices

Sometimes you may want to have project-specific advices. New developers joining a project may risk struggling with some vague compiler errors related to particular internal types. Clippy now allows defining a custom set of advices and keeping it in .clippy.json file in the project directory. Read more here.

Future plans

We are looking into further possibilities of leveraging ANSI colors in the output, like syntax highlighting. There may be also further enhancements to the presentantion of long type signatures. Contributions are very welcome, both code updates or new advice submissions, so don't hesitate to join the project!


Special thanks to Łukasz Żuchowski and Shane Delmore for these awesome contributions.

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