Scala compiler plugin for warning suppression
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Latest commit bb5abf4 Oct 15, 2018

Scala compiler plugin for warning suppression

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Scala has no local warning suppression (see e.g. scala/bug/issues/1781 for discussion). This plugin aims to change the situation. The direct motivation for this plugin is to be able to turn on -Xfatal-warnings option in Scala compiler and enforce zero-warning policy but still be able to consciously silent out warnings which would otherwise be a pointless noise.


If you're using SBT, simply add these lines to your build.sbt to enable the plugin:

val silencerVersion = "1.2.1"

libraryDependencies ++= Seq(
  compilerPlugin("com.github.ghik" %% "silencer-plugin" % silencerVersion),
  "com.github.ghik" %% "silencer-lib" % silencerVersion % Provided

Silencer currently works with Scala 2.11.4+, 2.12.0+ and 2.13.0-M4+. Also note that since both silencer-plugin and silencer-lib are compile time only dependencies, Silencer can also be used in ScalaJS and Scala Native without having to be cross compiled for it.

Annotation-based suppression

With the plugin enabled, warnings can be silenced using the @com.github.ghik.silencer.silent annotation. It can be applied on a single statement or expression, entire def/val/var definition or entire class/object/trait definition.

import com.github.ghik.silencer.silent

@silent class someClass { ... }
@silent def someMethod() = { ... }
someDeprecatedApi("something"): @silent

The @silent annotation suppresses all warnings in some code fragment. There is currently no way to silent out only specific classes of warnings, like with @SuppressWarnings annotation in Java.

Global regex-based suppression

You can also suppress warnings globally based on a warning message regex. In order to do that, pass this option to scalac:

scalacOptions += "-P:silencer:globalFilters=[semi-colon separated message patterns]"


Silencer is succesfully being used in AVSystem open source and closed projects, e.g. AVSystem Scala Commons Library