Drop 2.12 support, add scalafmt, scalafix, MiMa

Source and binary compat preserved.

The code changes:
- scalafmt and scalafix formatting applied
- added type annotations to public members and implicits
- migrated to Scala 3 syntax for imports
- since 2.12 is not supported anymore, replaced CurrentThreadExecutionContext wrapper with direct usage of ExecutionContext.parasitic. This as well leads to removal of the direct dependency on executor-tools as it is not used in the project anymore.

.github/workflows/ci.yml

@@ -11,7 +11,6 @@ jobs:
       matrix:
         scala:
           - 2.13.14
-          - 2.12.19
           - 3.3.3
 
     steps:
@@ -25,7 +24,7 @@ jobs:
           java-version: [email protected]
 
       - name: build ${{ matrix.scala }}
-        run: sbt ++${{ matrix.scala }} clean coverage test
+        run: sbt ++${{ matrix.scala }} clean check coverage test
 
       - name: test coverage
         if: success()

.scalafix.conf

@@ -0,0 +1,7 @@
+rules = [OrganizeImports]
+
+OrganizeImports {
+  preset = INTELLIJ_2020_3
+  removeUnused = false # `true` is not supported in Scala 3.3.0
+  targetDialect = Auto
+}

.scalafmt.conf

@@ -0,0 +1,40 @@
+version = 3.8.3
+
+runner.dialect = scala213source3
+
+maxColumn = 110
+trailingCommas = multiple
+
+align.preset = some
+indent.defnSite = 2
+indent.caseSite = 5
+indent.extendSite = 2
+indentOperator.exclude = "^(&&|\\|\\||~)$"
+newlines.avoidForSimpleOverflow = [punct, tooLong, slc]
+newlines.source = keep
+newlines.implicitParamListModifierForce = [after]
+spaces.beforeContextBoundColon = always
+spaces.inInterpolatedStringCurlyBraces = true
+verticalMultiline.atDefnSite = true
+verticalMultiline.arityThreshold = 3
+verticalMultiline.newlineAfterOpenParen = true
+danglingParentheses.exclude = []
+docstrings.oneline = fold
+docstrings.wrap = no
+importSelectors = singleLine
+
+rewrite.rules = [
+  RedundantParens,
+  SortModifiers,
+]
+
+rewrite.sortModifiers.order = [
+  "override",
+  "private",
+  "protected",
+  "implicit",
+  "final",
+  "sealed",
+  "abstract",
+  "lazy",
+]

benchmark/src/main/scala/com/evolutiongaming/concurrent/sequentially/Common.scala

@@ -1,25 +1,27 @@
 package com.evolutiongaming.concurrent.sequentially
 
-import java.util.concurrent.TimeUnit
+import org.openjdk.jmh.annotations.*
 
-import org.openjdk.jmh.annotations._
+import java.util.concurrent.TimeUnit
 
 @State(Scope.Benchmark)
 @Warmup(iterations = 5)
 @Measurement(iterations = 10)
-@Fork(value = 1, jvmArgs = Array(
-  "-server",
-  "-Xms1g",
-  "-Xmx1g",
-  "-XX:NewSize=512m",
-  "-XX:MaxNewSize=512m",
-  "-XX:InitialCodeCacheSize=256m",
-  "-XX:ReservedCodeCacheSize=256m",
-  "-XX:-UseBiasedLocking",
-  "-XX:+AlwaysPreTouch",
-  "-XX:+UseParallelGC"))
+@Fork(
+  value = 1,
+  jvmArgs = Array(
+    "-server",
+    "-Xms1g",
+    "-Xmx1g",
+    "-XX:NewSize=512m",
+    "-XX:MaxNewSize=512m",
+    "-XX:InitialCodeCacheSize=256m",
+    "-XX:ReservedCodeCacheSize=256m",
+    "-XX:-UseBiasedLocking",
+    "-XX:+AlwaysPreTouch",
+    "-XX:+UseParallelGC",
+  ),
+)
 @BenchmarkMode(Array(Mode.Throughput))
 @OutputTimeUnit(TimeUnit.SECONDS)
-abstract class Common {
-
-}
+abstract class Common {}

benchmark/src/main/scala/com/evolutiongaming/concurrent/sequentially/SequentiallyAsyncBenchmark.scala

@@ -5,7 +5,7 @@ import akka.stream.Materializer
 import org.openjdk.jmh.annotations.{Benchmark, Level, Setup, TearDown}
 
 import scala.concurrent.Await
-import scala.concurrent.duration._
+import scala.concurrent.duration.*
 
 class SequentiallyAsyncBenchmark extends Common {
 

benchmark/src/main/scala/com/evolutiongaming/concurrent/sequentially/SequentiallyBenchmark.scala

@@ -1,11 +1,10 @@
 package com.evolutiongaming.concurrent.sequentially
 
 import akka.actor.ActorSystem
-import org.openjdk.jmh.annotations._
+import org.openjdk.jmh.annotations.*
 
 import scala.concurrent.Await
-import scala.concurrent.duration._
-
+import scala.concurrent.duration.*
 
 class SequentiallyBenchmark extends Common {
 
@@ -28,4 +27,4 @@ class SequentiallyBenchmark extends Common {
     Await.ready(system.terminate(), 15.seconds)
     ()
   }
-}
+}

benchmark/src/main/scala/com/evolutiongaming/concurrent/sequentially/SequentiallyHandlerBenchmark.scala

@@ -5,7 +5,7 @@ import akka.stream.Materializer
 import org.openjdk.jmh.annotations.{Benchmark, Level, Setup, TearDown}
 
 import scala.concurrent.Await
-import scala.concurrent.duration._
+import scala.concurrent.duration.*
 
 class SequentiallyHandlerBenchmark extends Common {
 
@@ -32,4 +32,3 @@ class SequentiallyHandlerBenchmark extends Common {
     ()
   }
 }
-

benchmark/src/main/scala/com/evolutiongaming/concurrent/sequentially/SequentiallyStreamBenchmark.scala

@@ -5,7 +5,7 @@ import akka.stream.Materializer
 import org.openjdk.jmh.annotations.{Benchmark, Level, Setup, TearDown}
 
 import scala.concurrent.Await
-import scala.concurrent.duration._
+import scala.concurrent.duration.*
 
 class SequentiallyStreamBenchmark extends Common {
 

build.sbt

@@ -1,39 +1,50 @@
 lazy val commonSettings = Seq(
   organization := "com.evolutiongaming",
-  homepage := Some(new URL("http://github.com/evolution-gaming/sequentially")),
+  homepage := Some(url("https://github.com/evolution-gaming/sequentially")),
   startYear := Some(2018),
   organizationName := "Evolution",
-  organizationHomepage := Some(url("http://evolution.com")),
+  organizationHomepage := Some(url("https://evolution.com")),
   scalaVersion := crossScalaVersions.value.head,
-  crossScalaVersions := Seq("2.13.14", "2.12.19", "3.3.3"),
+  crossScalaVersions := Seq("2.13.14", "3.3.3"),
+  Compile / scalacOptions ++= {
+    if (scalaBinaryVersion.value == "2.13") {
+      Seq(
+        "-Xsource:3"
+      )
+    } else Seq.empty
+  },
   Compile / doc / scalacOptions += "-no-link-warnings",
   publishTo := Some(Resolver.evolutionReleases),
   licenses := Seq(("MIT", url("https://opensource.org/licenses/MIT"))),
   releaseCrossBuild := true,
-  versionScheme := Some("semver-spec"))
+  versionScheme := Some("semver-spec"),
+)
 
+// Your next release will be binary compatible with the previous one,
+// but it may not be source compatible (ie, it will be a minor release).
+ThisBuild / versionPolicyIntention := Compatibility.BinaryAndSourceCompatible
 
 lazy val root = (project
   in file(".")
   settings (name := "sequentially-root")
   settings commonSettings
   settings (publish / skip := true)
-  aggregate(sequentially, benchmark, `sequentially-metrics`))
+  aggregate (sequentially, benchmark, `sequentially-metrics`))
 
 lazy val sequentially = (project
   in file("sequentially")
   settings (name := "sequentially")
   settings commonSettings
   settings (libraryDependencies ++= Seq(
-    "com.typesafe.akka"   %% "akka-stream"    % "2.6.21",
-    "com.typesafe.akka"   %% "akka-testkit"   % "2.6.21" % Test,
-    "com.evolutiongaming" %% "executor-tools" % "1.0.4",
-    "com.evolutiongaming" %% "future-helper"  % "1.0.7",
-    "org.scalatest"       %% "scalatest"      % "3.2.10" % Test)))
+    "com.typesafe.akka" %% "akka-stream" % "2.6.21",
+    "com.typesafe.akka" %% "akka-testkit" % "2.6.21" % Test,
+    "com.evolutiongaming" %% "future-helper" % "1.0.7",
+    "org.scalatest" %% "scalatest" % "3.2.10" % Test,
+  )))
 
 lazy val benchmark = (project
   in file("benchmark")
-  enablePlugins(JmhPlugin)
+  enablePlugins JmhPlugin
   settings (name := "benchmark")
   settings commonSettings
   dependsOn sequentially)
@@ -47,4 +58,10 @@ lazy val `sequentially-metrics` = (project
     "com.evolutiongaming" %% "prometheus-tools" % "1.0.8"
   )))
 
-addCommandAlias("check", "show version")
+//used by evolution-gaming/scala-github-actions
+addCommandAlias(
+  "check",
+  "all versionPolicyCheck Compile/doc scalafmtCheckAll scalafmtSbtCheck; scalafixEnable; scalafixAll --check",
+)
+
+addCommandAlias("fmtAll", "all scalafmtAll scalafmtSbt; scalafixEnable; scalafixAll")

project/plugins.sbt

@@ -1,11 +1,9 @@
 addSbtPlugin("com.evolution" % "sbt-artifactory-plugin" % "0.0.2")
-
 addSbtPlugin("org.scoverage" % "sbt-scoverage" % "2.0.12")
-
 addSbtPlugin("org.scoverage" % "sbt-coveralls" % "1.3.11")
-
 addSbtPlugin("com.github.sbt" % "sbt-release" % "1.4.0")
-
+addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.4.3")
+addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.12.1")
 addSbtPlugin("com.evolution" % "sbt-scalac-opts-plugin" % "0.0.9")
-
-addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.4.3")
+addSbtPlugin("ch.epfl.scala" % "sbt-version-policy" % "3.2.1")
+addSbtPlugin("pl.project13.scala" % "sbt-jmh" % "0.4.3")

sequentially-metrics/src/main/scala/com/evolutiongaming/concurrent/MeteredSequentiallyAsync.scala

@@ -6,27 +6,30 @@ import scala.concurrent.Future
 
 object MeteredSequentiallyAsync {
 
-  def apply[K](sequentially: SequentiallyAsync[K],
-               name: String,
-               sequentiallyMetrics: SequentiallyMetrics.Factory,
+  def apply[K](
+    sequentially: SequentiallyAsync[K],
+    name: String,
+    sequentiallyMetrics: SequentiallyMetrics.Factory,
   ): SequentiallyAsync[K] = {
     apply(sequentially, sequentiallyMetrics(name))
   }
 
-  def apply[K](sequentially: SequentiallyAsync[K],
-               metrics: SequentiallyMetrics,
-  ): SequentiallyAsync[K] = new SequentiallyAsync[K] {
-    def async[KK <: K, T](key: K)(task: => Future[T]): Future[T] = {
-      val start = System.nanoTime()
+  def apply[K](
+    sequentially: SequentiallyAsync[K],
+    metrics: SequentiallyMetrics,
+  ): SequentiallyAsync[K] =
+    new SequentiallyAsync[K] {
+      def async[KK <: K, T](key: K)(task: => Future[T]): Future[T] = {
+        val start = System.nanoTime()
 
-      def run(): Future[T] = {
-        metrics.queue(start)
-        metrics.run(task)
-      }
+        def run(): Future[T] = {
+          metrics.queue(start)
+          metrics.run(task)
+        }
 
-      sequentially.async(key)(run())
+        sequentially.async(key)(run())
+      }
     }
-  }
 
   trait Factory {
     def apply[K](name: String): SequentiallyAsync[K]
@@ -38,8 +41,9 @@ object MeteredSequentiallyAsync {
       def apply[K]: SequentiallyAsync[K]
     }
 
-    def apply(provider: Provider,
-              sequentiallyMetrics: SequentiallyMetrics.Factory,
+    def apply(
+      provider: Provider,
+      sequentiallyMetrics: SequentiallyMetrics.Factory,
     ): Factory = new Factory {
       override def apply[K](name: String): SequentiallyAsync[K] =
         MeteredSequentiallyAsync(provider.apply[K], sequentiallyMetrics(name))

sequentially-metrics/src/main/scala/com/evolutiongaming/concurrent/SequentiallyMetrics.scala

@@ -1,6 +1,6 @@
 package com.evolutiongaming.concurrent
 
-import com.evolutiongaming.prometheus.PrometheusHelper._
+import com.evolutiongaming.prometheus.PrometheusHelper.*
 import io.prometheus.client.{CollectorRegistry, Summary}
 
 import scala.concurrent.Future
@@ -13,30 +13,27 @@ trait SequentiallyMetrics {
 object SequentiallyMetrics {
 
   def empty: SequentiallyMetrics = new SequentiallyMetrics {
-    def queue(startNanos: Long): Unit           = ()
+    def queue(startNanos: Long): Unit = ()
     def run[T](future: => Future[T]): Future[T] = future
   }
 
-  /**
-   * name: String => SequentiallyMetrics
-   */
+  /** name: String => SequentiallyMetrics */
   type Factory = String => SequentiallyMetrics
 
   object Factory {
 
     def empty: Factory = _ => SequentiallyMetrics.empty
 
-    /**
-     * @note Must be singleton as metric names must be unique.
-     * @see CollectorRegistry#register
-     */
+    /** @note Must be singleton as metric names must be unique.
+      * @see CollectorRegistry#register
+      */
     def apply(
-               prometheusRegistry: CollectorRegistry,
-               prefix: String = "sequentially",
-             ): Factory = {
+      prometheusRegistry: CollectorRegistry,
+      prefix: String = "sequentially",
+    ): Factory = {
       val time = Summary
         .build()
-        .name(s"${prefix}_time")
+        .name(s"${ prefix }_time")
         .help("Latency of Sequentially operations (queue, run) (by name)")
         .labelNames("name", "operation")
         .defaultQuantiles()