Allow opt out of code discipline (#28588)

.sbt-java-formatter.conf

@@ -10,7 +10,7 @@ ignored-files = [
   "ProtobufProtocol.java"
 ]
 
-//ignore by pacakges:
+//ignore by packages:
 //  1. adated source code
 //  2. protobuf generated messages
 ignored-packages = [

CONTRIBUTING.md

@@ -427,14 +427,21 @@ Preferences > Editor > Code Style > Scala, select Scalafmt as formatter and enab
 IntelliJ will then use the same settings and version as defined in `.scalafmt.conf` file. Then it's
 not needed to use `sbt scalafmtAll` when editing with IntelliJ.
 
+PR validation includes checking that the Scala sources are formatted and will fail if they are not.
+
 ### Java style
 
-Java code is currently not automatically reformatted by sbt (expecting to have a plugin to do this soon).
+Akka uses [the sbt Java Formatter plugin](https://github.com/sbt/sbt-java-formatter) to format Java sources.
-Thus we ask Java contributions to follow these simple guidelines:
 
-- 2 spaces
+PR validation includes checking that the Java sources are formatted and will fail if they are not.
-- `{` on same line as method name
+
-- in all other aspects, follow the [Oracle Java Style Guide](http://www.oracle.com/technetwork/java/codeconvtoc-136057.html)
+### Code discipline opt out
+
+In addition to formatting the Akka build enforces code discipline through a set of compiler flags. While exploring ideas
+the discipline may be more of a hindrance than a help so it is possible to disable it by setting the system property `akka.no.discipline`
+to any non-empty string value when starting up sbt: `sbt -Dakka.no.discipline=youbet`
+
+PR validation includes the discipline flags and therefore may fail if the flags were disabled during development. Make sure you compile your code at least once with discipline enabled before sending a PR.
 
 ### Preferred ways to use timeouts in tests
 

project/AkkaDisciplinePlugin.scala

@@ -16,6 +16,9 @@ object AkkaDisciplinePlugin extends AutoPlugin with ScalafixSupport {
   override def requires: Plugins = JvmPlugin && ScalafixPlugin
   override lazy val projectSettings = disciplineSettings
 
+  // allow toggling for pocs/exploration of ideas without discpline
+  val enabled = !sys.props.contains("akka.no.discipline")
+
   // We allow warnings in docs to get the 'snippets' right
   val nonFatalWarningsFor = Set("akka-docs")
 
@@ -40,8 +43,7 @@ object AkkaDisciplinePlugin extends AutoPlugin with ScalafixSupport {
     "akka-stream-testkit",
     "akka-stream-tests",
     "akka-stream-tests-tck",
-    "akka-testkit",
+    "akka-testkit")
-  )
 
   lazy val scalaFixSettings = Seq(Compile / scalacOptions += "-Yrangepos")
 
@@ -54,40 +56,44 @@ object AkkaDisciplinePlugin extends AutoPlugin with ScalafixSupport {
   }
 
   lazy val disciplineSettings =
-    scalaFixSettings ++
+    if (enabled) {
-    silencerSettings ++ Seq(
+      scalaFixSettings ++
-      Compile / scalacOptions ++= (
+      silencerSettings ++ Seq(
-          if (!nonFatalWarningsFor(name.value)) Seq("-Xfatal-warnings")
+        Compile / scalacOptions ++= (
-          else Seq.empty
+            if (!nonFatalWarningsFor(name.value)) Seq("-Xfatal-warnings")
-        ),
+            else Seq.empty
-      Test / scalacOptions --= testUndicipline,
+          ),
-      Compile / scalacOptions ++= (CrossVersion.partialVersion(scalaVersion.value) match {
+        Test / scalacOptions --= testUndicipline,
-          case Some((2, 13)) =>
+        Compile / scalacOptions ++= (CrossVersion.partialVersion(scalaVersion.value) match {
-            disciplineScalacOptions -- Set(
+            case Some((2, 13)) =>
-              "-Ywarn-inaccessible",
+              disciplineScalacOptions -- Set(
-              "-Ywarn-infer-any",
+                "-Ywarn-inaccessible",
-              "-Ywarn-nullary-override",
+                "-Ywarn-infer-any",
-              "-Ywarn-nullary-unit",
+                "-Ywarn-nullary-override",
-              "-Ypartial-unification",
+                "-Ywarn-nullary-unit",
-              "-Yno-adapted-args")
+                "-Ypartial-unification",
-          case Some((2, 12)) =>
+                "-Yno-adapted-args")
-            disciplineScalacOptions
+            case Some((2, 12)) =>
-          case _ =>
+              disciplineScalacOptions
-            Nil
+            case _ =>
-        }).toSeq,
+              Nil
-      Compile / scalacOptions --=
+          }).toSeq,
-        (if (looseProjects.contains(name.value)) undisciplineScalacOptions.toSeq
+        Compile / scalacOptions --=
-         else Seq.empty),
+          (if (looseProjects.contains(name.value)) undisciplineScalacOptions.toSeq
-      // Discipline is not needed for the docs compilation run (which uses
+           else Seq.empty),
-      // different compiler phases from the regular run), and in particular
+        // Discipline is not needed for the docs compilation run (which uses
-      // '-Ywarn-unused:explicits' breaks 'sbt ++2.13.0-M5 akka-actor/doc'
+        // different compiler phases from the regular run), and in particular
-      // https://github.com/akka/akka/issues/26119
+        // '-Ywarn-unused:explicits' breaks 'sbt ++2.13.0-M5 akka-actor/doc'
-      Compile / doc / scalacOptions --= disciplineScalacOptions.toSeq :+ "-Xfatal-warnings",
+        // https://github.com/akka/akka/issues/26119
-      // having discipline warnings in console is just an annoyance
+        Compile / doc / scalacOptions --= disciplineScalacOptions.toSeq :+ "-Xfatal-warnings",
-      Compile / console / scalacOptions --= disciplineScalacOptions.toSeq)
+        // having discipline warnings in console is just an annoyance
+        Compile / console / scalacOptions --= disciplineScalacOptions.toSeq)
+    } else {
+      // we still need these in opt-out since the annotations are present
+      silencerSettings ++ Seq(Compile / scalacOptions += "-deprecation")
+    }
 
-  val testUndicipline = Seq(
+  val testUndicipline = Seq("-Ywarn-dead-code" // '???' used in compile only specs
-    "-Ywarn-dead-code", // '???' used in compile only specs
   )
 
   /**