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https://github.com/typelevel/sbt-tpolecat

scalac options for the enlightened
https://github.com/typelevel/sbt-tpolecat

compiler-options sbt sbt-plugin scala

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scalac options for the enlightened

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## sbt-tpolecat

[![Build Status](https://github.com/typelevel/sbt-tpolecat/workflows/CI/badge.svg)](https://github.com/typelevel/sbt-tpolecat/actions?query=workflow%3ACI)
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[![Latest Version](https://index.scala-lang.org/typelevel/sbt-tpolecat/sbt-tpolecat/latest.svg)](https://index.scala-lang.org/typelevel/sbt-tpolecat/sbt-tpolecat)

### scalac options for the enlightened

sbt-tpolecat is an SBT plugin for automagically configuring scalac options according to the project Scala version, inspired by Rob Norris ([@tpolecat](https://github.com/tpolecat))'s excellent series of blog posts providing [recommended options](https://tpolecat.github.io/2017/04/25/scalac-flags.html) to get the most out of the compiler.

As of version 0.1.11, it also supports setting options for Scala 3.x.

### Usage

Add the following to your project's `project/plugins.sbt`:

```scala
addSbtPlugin("org.typelevel" % "sbt-tpolecat" % "0.5.2")
```

Once you are using this plugin we recommend that you don't manipulate the `scalacOptions` key directly.

Instead you should modify the `tpolecatScalacOptions` key or the options key for the relevant mode, for example `tpolecatDevModeOptions` for the development mode.

### Excluding specific warnings

To exclude an individual warning, say to ignore unused imports during testing, you can add the following to your configuration:

```scala
import org.typelevel.scalacoptions.ScalacOptions

Test / tpolecatExcludeOptions += ScalacOptions.warnUnusedImports
```

If you would like to exclude more than one warning, you can add a `Set` of scalac options, like so:

```scala
import org.typelevel.scalacoptions.ScalacOptions

Test / tpolecatExcludeOptions ++= Set(
ScalacOptions.warnValueDiscard,
ScalacOptions.warnUnusedImports,
ScalacOptions.warnUnusedLocals
)
```

### ScalaTest warnings

One of the options configured by **sbt-tpolecat** (`-Wnonunit-statement`) is designed to warn users about discarded values in their code.

However, Scalatest assertions return a value of type `Assertion` by design, in order to support async testing.

Unfortunately, this means that in synchronous test suites, every assertion discards this `Assertion` value, triggering the `-Wnonunit-statement` compiler warning.

If you find yourself in this situation, you can disable the `-Wnonunit-statement` option in your test suite like so:

```scala
import org.typelevel.scalacoptions.ScalacOptions

Test / tpolecatExcludeOptions += ScalacOptions.warnNonUnitStatement
```

### Configuring the REPL

To filter out scala compiler options that don't work well in the REPL, use the `tpolecatExcludeOptions`.

By default, the plugin only applies this filter to the `console` task in the `Compile` and `Test` configurations.

For example, to apply this filter to the `console` task in the `IntegrationTest` configuration you can do the following:

```scala
IntegrationTest / console / tpolecatExcludeOptions ++= ScalacOptions.defaultConsoleExclude
```

### Modes

This plugin can be used in several modes. The default mode is the continuous integration mode.

Modes can be selected by using mode switching commands, or by setting environment variables.

When multiple mode-setting environment variables are defined, the most restrictive mode is selected. For example, if the `SBT_TPOLECAT_DEV` and `SBT_TPOLECAT_CI` variables are both defined, continuous integration mode will be enabled.

You can customise the default mode by modifying the `ThisBuild / tpolecatDefaultOptionsMode` key. Default is `CiMode`, and the available modes are `org.typelevel.sbt.tpolecat.{CiMode, DevMode, ReleaseMode, VerboseMode}`.

#### Development mode

To enable the development mode, use the `tpolecatDevMode` command or define the environment variable `SBT_TPOLECAT_DEV`.

In this mode a baseline set of scala compiler options are enabled.

You can customise the options that are enabled in this mode by modifying the `tpolecatDevModeOptions` key. Default: `ScalacOptions.default`.

For example, to disable macros you could customise the development mode options as follows:

```scala
tpolecatDevModeOptions ~= { opts =>
opts.filterNot(Set(ScalacOptions.languageExperimentalMacros))
}
```

You can customise the environment variable that is used to enable this mode by modifying the `ThisBuild / tpolecatDevModeEnvVar` key. Default: `"SBT_TPOLECAT_DEV"`.

#### Verbose mode

To enable the verbose mode, use the `tpolecatVerboseMode` command or define the environment variable `SBT_TPOLECAT_VERBOSE`.

In this mode all development mode options are enabled, and several verbose options that are commonly used for debugging implicit resolution and providing detailed compile errors are enabled.

You can customise the options that are enabled in this mode by modifying the `tpolecatVerboseModeOptions` key. Default: `tpolecatDevModeOptions.value ++ ScalacOptions.verboseOptions`.

For example, to disable verbose implicit logging you could customise the verbose mode options as follows:

```scala
tpolecatVerboseModeOptions ~= { opts =>
opts.filterNot(Set(ScalacOptions.verboseImplicits))
}
```

You can customise the environment variable that is used to enable this mode by modifying the `ThisBuild / tpolecatVerboseModeEnvVar` key. Default: `"SBT_TPOLECAT_VERBOSE"`.

#### Continuous integration mode

To enable the continuous integration mode, use the `tpolecatCiMode` command or define the environment variable `SBT_TPOLECAT_CI`.

In this mode all development mode options are enabled, and the fatal warnings option (`-Xfatal-warnings` ) is added.

You can customise the options that are enabled in this mode by modifying the `tpolecatCiModeOptions` key. Default: `tpolecatDevModeOptions.value + ScalacOptions.fatalWarnings`.

For example, to disable unused linting you could customise the CI options as follows:

```scala
tpolecatCiModeOptions ~= { opts =>
opts.filterNot(
ScalacOptions.privateWarnUnusedOptions ++
ScalacOptions.warnUnusedOptions
)
}
```

You can customise the environment variable that is used to enable this mode by modifying the `ThisBuild / tpolecatCiModeEnvVar` key. Default: `"SBT_TPOLECAT_CI"`.

#### Release mode

To enable the release mode, use the `tpolecatReleaseMode` command or define the environment variable `SBT_TPOLECAT_RELEASE`.

In this mode all CI mode options are enabled, and the method-local optimisation option (`-opt:l:method`) is enabled if available for your Scala version.

You can customise the options that are enabled in this mode by modifying the `tpolecatReleaseModeOptions` key. Default: `tpolecatCiModeOptions.value + ScalacOptions.optimizerMethodLocal`.

For example, to enable inlining within your library or application's packages you could customise the release options as follows:

```scala
tpolecatReleaseModeOptions ++= ScalacOptions.optimizerOptions("your.library.**")
```

To understand more about the Scala optimizer read [The Scala 2.12 / 2.13 Inliner and Optimizer](https://docs.scala-lang.org/overviews/compiler-options/optimizer.html).

You can customise the environment variable that is used to enable this mode by modifying the `ThisBuild / tpolecatReleaseModeEnvVar` key. Default: `"SBT_TPOLECAT_RELEASE"`.

### Caveat

I can't promise this plugin will work for old minor releases of Scala.

It is currently tested with Scala 2.x releases:

* 2.13.8
* 2.12.16
* 2.11.12

and Scala 3.x releases:

* 3.0.2
* 3.1.3
* 3.3.0
* 3.3.1

### Conduct

Participants are expected to follow the [Scala Code of Conduct](https://www.scala-lang.org/conduct/) while discussing the project on GitHub and any other venues associated with the project.

### License

All code in this repository is licensed under the Apache License, Version 2.0. See [LICENSE](./LICENSE).