Improve balancing with JUnit reports support

.github/workflows/release.yml

@@ -7,14 +7,17 @@ jobs:
   publish:
     runs-on: ubuntu-20.04
     steps:
-      - uses: actions/checkout@v2.3.4
+      - uses: actions/checkout@v3
         with:
           fetch-depth: 0
-      - uses: olafurpg/setup-scala@v13
-      - uses: olafurpg/setup-gpg@v3
+      - uses: actions/setup-java@v3
+        with:
+          distribution: temurin
+          java-version: 8
+          cache: sbt
       - run: sbt ci-release
         env:
           PGP_PASSPHRASE: ${{ secrets.PGP_PASSPHRASE }}
           PGP_SECRET: ${{ secrets.PGP_SECRET }}
           SONATYPE_PASSWORD: ${{ secrets.SONATYPE_PASSWORD }}
-          SONATYPE_USERNAME: ${{ secrets.SONATYPE_USERNAME }}
+          SONATYPE_USERNAME: ${{ secrets.SONATYPE_USERNAME }}

.github/workflows/scala.yml

@@ -7,16 +7,20 @@ on:
     branches: [master, main]
 
 jobs:
-  build:
+  jvm:
+    strategy:
+      fail-fast: false
+      matrix:
+        scala: [2.12.18]
+        java: [[email protected], [email protected]]
     runs-on: ubuntu-latest
-
     steps:
       - uses: actions/checkout@v2
 
-      - name: Set up JDK 11
-        uses: actions/setup-java@v1
+      - name: Set up environment
+        uses: olafurpg/setup-scala@v10
         with:
-          java-version: 11
+          java-version: ${{ matrix.java }}
 
       - name: Run tests
-        run: sbt -Dscalac.unused.enabled=true fmtCheck test
+        run: sbt ++${{ matrix.scala}} fmtCheck test

.scalafmt.conf

@@ -1,18 +1,44 @@
-version = "3.2.1"
+version = 3.7.14
 
-runner.dialect = scala213
+runner.dialect = scala213source3
 
-maxColumn = 120
-align.preset = most
-continuationIndent.defnSite = 2
+align = none
+maxColumn = 120 # For wide displays.
 assumeStandardLibraryStripMargin = true
+align.tokens = [{code = "=>", owner = "Case"}, {code = "<-"}]
+align.allowOverflow = true
+align.arrowEnumeratorGenerator = true
+align.openParenCallSite = false
+align.openParenDefnSite = false
+newlines.topLevelStatementBlankLines = [
+  {blanks {before = 1}}
+  {regex = "^Import|^Term.ApplyInfix"}
+]
+newlines.alwaysBeforeElseAfterCurlyIf = false
+indentOperator.topLevelOnly = true
 docstrings.style = SpaceAsterisk
-lineEndings = preserve
+docstrings.wrapMaxColumn = 80
+
 includeCurlyBraceInSelectChains = false
-danglingParentheses.preset = true
-spaces {
-  inImportCurlyBraces = true
-}
-optIn.annotationNewlines = true
+includeNoParensInSelectChains = false
+
+rewrite.rules = [SortModifiers, PreferCurlyFors, SortImports, RedundantBraces]
+rewrite.scala3.convertToNewSyntax = true
+rewrite.imports.groups = [
+  [".*"],
+  ["java\\..*", "javax\\..*", "scala\\..*"]
+]
+
+project.excludeFilters = ["/target/"]
+
+lineEndings = preserve
 
-rewrite.rules = [SortImports, RedundantBraces]
+fileOverride {
+  "glob:**/*.sbt" {
+    runner.dialect = sbt1
+    rewrite.scala3.convertToNewSyntax = false
+  }
+  "glob:**/project/*.scala" {
+    rewrite.scala3.convertToNewSyntax = false
+  }
+}

build.sbt

@@ -1,21 +1,25 @@
-import sbtwelcome._
+import sbtwelcome.*
 
 inThisBuild(
   List(
     organization := "com.github.reibitto",
-    homepage     := Some(url("https://github.com/reibitto/sbt-test-shards")),
-    licenses     := List("Apache-2.0" -> url("https://www.apache.org/licenses/LICENSE-2.0")),
-    developers   := List(
+    homepage := Some(url("https://github.com/reibitto/sbt-test-shards")),
+    licenses := List("Apache-2.0" -> url("https://www.apache.org/licenses/LICENSE-2.0")),
+    developers := List(
       Developer("reibitto", "reibitto", "[email protected]", url("https://reibitto.github.io"))
     )
   )
 )
 
 lazy val root = (project in file(".")).settings(
-  name         := "sbt-test-shards",
+  name := "sbt-test-shards",
   organization := "com.github.reibitto",
-  scalaVersion := "2.12.16",
-  sbtPlugin    := true
+  scalaVersion := "2.12.18",
+  sbtPlugin := true,
+  libraryDependencies ++= Seq(
+    "org.scalameta" %% "munit" % "0.7.29" % Test,
+    "org.scalameta" %% "munit-scalacheck" % "0.7.29" % Test
+  )
 )
 
 addCommandAlias("fmt", "all root/scalafmtSbt root/scalafmtAll")
@@ -41,9 +45,9 @@ logo :=
      |""".stripMargin
 
 usefulTasks := Seq(
-  UsefulTask("a", "~compile", "Compile with file-watch enabled"),
-  UsefulTask("b", "fmt", "Run scalafmt on the entire project"),
-  UsefulTask("c", "publishLocal", "Publish the sbt plugin locally so that you can consume it from a different project")
+  UsefulTask("~compile", "Compile with file-watch enabled"),
+  UsefulTask("fmt", "Run scalafmt on the entire project"),
+  UsefulTask("publishLocal", "Publish the sbt plugin locally so that you can consume it from a different project")
 )
 
 logoColor := scala.Console.MAGENTA

project/build.properties

@@ -1 +1 @@
-sbt.version=1.7.1
+sbt.version=1.9.7

project/plugins.sbt

@@ -1,3 +1,5 @@
-addSbtPlugin("org.scalameta"       % "sbt-scalafmt"   % "2.4.6")
-addSbtPlugin("com.github.sbt"      % "sbt-ci-release" % "1.5.10")
-addSbtPlugin("com.github.reibitto" % "sbt-welcome"    % "0.2.2")
+addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.2")
+
+addSbtPlugin("com.github.sbt" % "sbt-ci-release" % "1.5.12")
+
+addSbtPlugin("com.github.reibitto" % "sbt-welcome" % "0.4.0")

src/main/scala/sbttestshards/ShardingAlgorithm.scala

@@ -1,6 +1,11 @@
 package sbttestshards
 
+import sbttestshards.parsers.JUnitReportParser
+
+import java.nio.charset.StandardCharsets
+import java.nio.file.Path
 import java.time.Duration
+import scala.util.hashing.MurmurHash3
 
 // This trait is open so that users can implement a custom `ShardingAlgorithm` if they'd like
 trait ShardingAlgorithm {
@@ -11,34 +16,60 @@ trait ShardingAlgorithm {
 
 object ShardingAlgorithm {
 
-  /** Shards by suite the name. This is the most reasonable default as it requires no additional setup. */
+  /** Shards by suite the name. This is the most reasonable default as it
+    * requires no additional setup.
+    */
   final case object SuiteName extends ShardingAlgorithm {
+
     override def shouldRun(specName: String, shardContext: ShardContext): Boolean =
-      // TODO: Test whether `hashCode` gets a good distribution. Otherwise implement a different hash algorithm.
-      specName.hashCode.abs % shardContext.testShardCount == shardContext.testShard
+      MurmurHash3
+        .bytesHash(specName.getBytes(StandardCharsets.UTF_8))
+        .abs % shardContext.testShardCount == shardContext.testShard
   }
 
-  /** Will always mark the test to run on this shard. Useful for debugging or for fallback algorithms. */
+  /** Will always mark the test to run on this shard. Useful for debugging or
+    * for fallback algorithms.
+    */
   final case object Always extends ShardingAlgorithm {
     override def shouldRun(specName: String, shardContext: ShardContext): Boolean = true
   }
 
-  /** Will never mark the test to run on this shard. Useful for debugging or for fallback algorithms. */
+  /** Will never mark the test to run on this shard. Useful for debugging or for
+    * fallback algorithms.
+    */
   final case object Never extends ShardingAlgorithm {
     override def shouldRun(specName: String, shardContext: ShardContext): Boolean = false
   }
 
-  /** Attempts to balance the shards by execution time so that no one shard takes significantly longer to complete than
-    * another.
+  object Balance {
+
+    def fromJUnitReports(
+        reportDirectories: Seq[Path],
+        shardsInfo: ShardingInfo,
+        fallbackShardingAlgorithm: ShardingAlgorithm = ShardingAlgorithm.SuiteName
+    ): Balance =
+      ShardingAlgorithm.Balance(
+        JUnitReportParser.parseDirectoriesRecursively(reportDirectories).testReports.map { r =>
+          SpecInfo(r.name, Some(Duration.ofMillis(r.timeTaken.toLong)))
+        },
+        shardsInfo,
+        fallbackShardingAlgorithm
+      )
+  }
+
+  /** Attempts to balance the shards by execution time so that no one shard
+    * takes significantly longer to complete than another.
     */
   final case class Balance(
-    tests: List[TestSuiteInfo],
-    bucketCount: Int,
-    fallbackShardingAlgorithm: ShardingAlgorithm = ShardingAlgorithm.SuiteName
+      specs: Seq[SpecInfo],
+      shardsInfo: ShardingInfo,
+      fallbackShardingAlgorithm: ShardingAlgorithm = ShardingAlgorithm.SuiteName
   ) extends ShardingAlgorithm {
+
     // TODO: Median might be better here?
     private val averageTime: Option[Duration] = {
-      val allTimeTaken = tests.flatMap(_.timeTaken)
+      val allTimeTaken = specs.flatMap(_.timeTaken)
+
       allTimeTaken.reduceOption(_.plus(_)).map { d =>
         if (allTimeTaken.isEmpty) Duration.ZERO
         else d.dividedBy(allTimeTaken.length)
@@ -48,14 +79,19 @@ object ShardingAlgorithm {
     // TODO: This uses a naive greedy algorithm for partitioning into approximately equal subsets. While this problem
     // is NP-complete, there's a lot of room for improvement with other algorithms. Dynamic programming should be
     // possible here.
-    private def createBucketMap(testShardCount: Int) = {
+    def distributeEvenly: Map[TestSuiteInfoSimple, Int] = {
       val durationOrdering: Ordering[Duration] = (a: Duration, b: Duration) => a.compareTo(b)
 
-      val allTests = tests
+      val allTests = specs
         .map(t => TestSuiteInfoSimple(t.name, t.timeTaken.getOrElse(averageTime.getOrElse(Duration.ZERO))))
         .sortBy(_.timeTaken)(durationOrdering.reverse)
 
-      val buckets = Array.fill(testShardCount)(TestBucket(Nil, Duration.ZERO))
+      val buckets = (0 until shardsInfo.shardCount).map { shardIndex =>
+        TestBucket(
+          tests = Nil,
+          sum = shardsInfo.initialDurations.getOrElse(shardIndex, Duration.ZERO)
+        )
+      }.toArray
 
       allTests.foreach { test =>
         val minBucket = buckets.minBy(_.sum)
@@ -66,14 +102,14 @@ object ShardingAlgorithm {
 
       buckets.zipWithIndex.flatMap { case (bucket, i) =>
         bucket.tests.map { info =>
-          info.name -> i
+          info -> i
         }
       }.toMap
     }
 
-    // `bucketCount` doesn't necessary need to match `testShardCount`, but ideally it should be a multiple of it.
-    // TODO: Maybe print a warning if it's not a multiple of it.
-    private val bucketMap: Map[String, Int] = createBucketMap(bucketCount)
+    private val bucketMap: Map[String, Int] = distributeEvenly.map { case (k, v) =>
+      k.name -> v
+    }
 
     def shouldRun(specName: String, shardContext: ShardContext): Boolean =
       bucketMap.get(specName) match {
@@ -82,6 +118,7 @@ object ShardingAlgorithm {
       }
   }
 
-  private final case class TestSuiteInfoSimple(name: String, timeTaken: Duration)
-  private final case class TestBucket(var tests: List[TestSuiteInfoSimple], var sum: Duration)
+  final case class TestSuiteInfoSimple(name: String, timeTaken: Duration)
+
+  final private case class TestBucket(var tests: List[TestSuiteInfoSimple], var sum: Duration)
 }

src/main/scala/sbttestshards/ShardingInfo.scala

@@ -0,0 +1,5 @@
+package sbttestshards
+
+import java.time.Duration
+
+final case class ShardingInfo(shardCount: Int, initialDurations: Map[Int, Duration] = Map.empty)

src/main/scala/sbttestshards/SpecBucketItem.scala

@@ -0,0 +1,5 @@
+package sbttestshards
+
+import java.time.Duration
+
+final case class SpecBucketItem(name: String, timeTaken: Duration)

src/main/scala/sbttestshards/SpecInfo.scala

@@ -0,0 +1,5 @@
+package sbttestshards
+
+import java.time.Duration
+
+final case class SpecInfo(name: String, timeTaken: Option[Duration])

src/main/scala/sbttestshards/TestShardsPlugin.scala

@@ -1,14 +1,15 @@
 package sbttestshards
 
-import sbt.Keys.*
 import sbt.*
+import sbt.Keys.*
 
 object TestShardsPlugin extends AutoPlugin {
+
   object autoImport {
-    val testShard         = settingKey[Int]("testShard")
-    val testShardCount    = settingKey[Int]("testShardCount")
+    val testShard = settingKey[Int]("testShard")
+    val testShardCount = settingKey[Int]("testShardCount")
     val shardingAlgorithm = settingKey[ShardingAlgorithm]("shardingAlgorithm")
-    val testShardDebug    = settingKey[Boolean]("testShardDebug")
+    val testShardDebug = settingKey[Boolean]("testShardDebug")
   }
 
   import autoImport.*
@@ -22,10 +23,10 @@ object TestShardsPlugin extends AutoPlugin {
 
   override lazy val projectSettings: Seq[Def.Setting[?]] =
     Seq(
-      testShard         := stringConfig("TEST_SHARD", "0").toInt,
-      testShardCount    := stringConfig("TEST_SHARD_COUNT", "1").toInt,
+      testShard := stringConfig("TEST_SHARD", "0").toInt,
+      testShardCount := stringConfig("TEST_SHARD_COUNT", "1").toInt,
       shardingAlgorithm := ShardingAlgorithm.SuiteName,
-      testShardDebug    := false,
+      testShardDebug := false,
       Test / testOptions += {
         val shardContext = ShardContext(testShard.value, testShardCount.value, sLog.value)
         Tests.Filter { specName =>