util/util-stats: scala 3 migration

**Problem**

Build util-stats with Scala 3

**Solution**

# Change util-stats project settings.
# Compile project + test with Scala 3 migration flags
# Remove flags
# Fix incompatibilities
# Run cross-building tests

**Result**

//Auto-rewrite fixes://
Scala 3 requires parentheses around the parameter of a lambda:
- DelegatingStatsReceiverTest.scala

//Other fixes://
Method `filterKeys` in trait MapOps is deprecated,
should use .view.filterKeys:
- CachedRegex.scala
- CategorizingExceptionStatsHandlerTest.scala
- MultiCategorizingExceptionStatsHandlerTest.scala

`schemaKey` method must be called with `()`:
- InMemoryStatsReceiver.scala

Implicit conversion `long2float` in object Long is deprecated,
need to be explicit:
- Stat.scala
- InMemoryStatsReceiverTest.scala
- ExpressionSchemaTest.scala

Cannot access apply method of case classes without specifying
package:
- Expression.scala

Types in implicit definitions need to be given explicitly:
- DelegatingStatsReceiverTest.scala

Note:
`print` changed to `println` in InMemoryStatsReceiver.scala to account for a
Scala 3 bug where the split method does not work properly in string
interpolation with special symbols.  See
https://jira.twitter.biz/browse/CSL-11259

JIRA Issues: CSL-11092

Differential Revision: https://phabricator.twitter.biz/D720514

Author: Michael Sutton

CHANGELOG.rst

@@ -6,18 +6,22 @@ Note that ``PHAB_ID=#`` and ``RB_ID=#`` correspond to associated messages in com
 
 Unreleased
 ----------
-* util-routing: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D727120``
 
-* util-sl4j-jul-bridge: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D726468``
+New Features
+~~~~~~~~~~~~
 
-* util-sl4j-api: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D725491``
+* util-cache: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D714304``.
 
 * util-cache-guava: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D716101``.
 
-* util-cache: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D714304``.
+* util-routing: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D727120``
+
+* util-sl4j-api: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D725491``
+
+* util-sl4j-jul-bridge: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D726468``
+
+* util-stats: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D720514``
 
-New Features
-~~~~~~~~~~~~
 * util-zk-test: Experimentally crossbuilds with Scala 3. ``PHAB_ID=D720603``
 
 21.8.0 (No 21.7.0 Release)

build.sbt

@@ -229,6 +229,18 @@ def scalatestMockitoVersionedDep(scalaVersion: String) = {
   }
 }
 
+def scalatestScalacheckVersionedDep(scalaVersion: String) = {
+  if (scalaVersion.startsWith("2")) {
+    Seq(
+      "org.scalatestplus" %% "scalacheck-1-14" % "3.1.2.0" % "test"
+    )
+  } else {
+    Seq(
+      "org.scalatestplus" %% "scalacheck-1-15" % "3.2.9.0" % "test"
+    )
+  }
+}
+ 
 lazy val util = Project(
   id = "util",
   base = file(".")
@@ -629,7 +641,7 @@ lazy val utilStats = Project(
   id = "util-stats",
   base = file("util-stats")
 ).settings(
-    sharedSettings
+    sharedScala3EnabledSettings
   ).settings(
     name := "util-stats",
     libraryDependencies ++= Seq(
@@ -638,16 +650,16 @@ lazy val utilStats = Project(
       scalacheckLib,
       "com.fasterxml.jackson.core" % "jackson-core" % jacksonVersion,
       "com.fasterxml.jackson.core" % "jackson-databind" % jacksonVersion,
-      "com.fasterxml.jackson.module" %% "jackson-module-scala" % jacksonVersion exclude ("com.google.guava", "guava"),
-      "org.mockito" % "mockito-core" % mockitoVersion % "test",
-      "org.scalatestplus" %% "mockito-3-3" % "3.1.2.0" % "test",
-      "org.scalatestplus" %% "scalacheck-1-14" % "3.1.2.0" % "test"
-    ) ++ {
+      ("com.fasterxml.jackson.module" %% "jackson-module-scala" % jacksonVersion exclude ("com.google.guava", "guava")).cross(CrossVersion.for3Use2_13),
+      "org.mockito" % "mockito-core" % mockitoVersion % "test"
+    ) ++ scalatestMockitoVersionedDep(scalaVersion.value)
+    ++ scalatestScalacheckVersionedDep(scalaVersion.value)
+    ++ {
       CrossVersion.partialVersion(scalaVersion.value) match {
-        case Some((2, major)) if major >= 13 =>
-          Seq("org.scala-lang.modules" %% "scala-parallel-collections" % "0.2.0" % "test")
-        case _ =>
+        case Some((2, major)) if major <= 12 =>
           Seq()
+        case _ =>
+          Seq("org.scala-lang.modules" %% "scala-parallel-collections" % "1.0.3" % "test")
       }
     }
   ).dependsOn(utilCore, utilLint)

util-stats/src/main/scala/com/twitter/finagle/stats/CachedRegex.scala

@@ -2,6 +2,7 @@ package com.twitter.finagle.stats
 
 import java.util.concurrent.ConcurrentHashMap
 import java.util.function.Consumer
+import scala.collection.compat._
 import scala.util.matching.Regex
 
 /**
@@ -50,6 +51,6 @@ private[stats] class CachedRegex(regex: Regex)
           }
         }
       })
-    samples.filterKeys(filterFn).toMap
+    samples.view.filterKeys(filterFn).toMap
   }
 }

util-stats/src/main/scala/com/twitter/finagle/stats/InMemoryStatsReceiver.scala

@@ -199,7 +199,7 @@ class InMemoryStatsReceiver extends StatsReceiver with WithHistogramDetails {
       p.println("---------")
     }
     for ((k, v) <- sortedCounters)
-      p.print(f"$k%s $v%d\n")
+      p.println(f"$k%s $v%d")
     if (includeHeaders && sortedGauges.nonEmpty) {
       p.println("\nGauges:")
       p.println("-------")
@@ -264,7 +264,7 @@ class InMemoryStatsReceiver extends StatsReceiver with WithHistogramDetails {
    * Designed to match the behavior of Metrics::registerExpression().
    */
   override protected[finagle] def registerExpression(schema: ExpressionSchema): Unit = {
-    expressions.put(schema.schemaKey, schema)
+    expressions.put(schema.schemaKey(), schema)
   }
 
   /**

util-stats/src/main/scala/com/twitter/finagle/stats/Stat.scala

@@ -37,7 +37,7 @@ object Stat {
     try {
       f
     } finally {
-      stat.add(elapsed().inUnit(unit))
+      stat.add(elapsed().inUnit(unit).toFloat)
     }
   }
 
@@ -52,10 +52,12 @@ object Stat {
   def timeFuture[A](stat: Stat, unit: TimeUnit)(f: => Future[A]): Future[A] = {
     val start = Stopwatch.timeNanos()
     try {
-      f.respond { _ => stat.add(unit.convert(Stopwatch.timeNanos() - start, TimeUnit.NANOSECONDS)) }
+      f.respond { _ =>
+        stat.add(unit.convert(Stopwatch.timeNanos() - start, TimeUnit.NANOSECONDS).toFloat)
+      }
     } catch {
       case NonFatal(e) =>
-        stat.add(unit.convert(Stopwatch.timeNanos() - start, TimeUnit.NANOSECONDS))
+        stat.add(unit.convert(Stopwatch.timeNanos() - start, TimeUnit.NANOSECONDS).toFloat)
         Future.exception(e)
     }
   }

util-stats/src/main/scala/com/twitter/finagle/stats/exp/Expression.scala

@@ -86,25 +86,26 @@ private[twitter] sealed trait Expression {
 /**
  * Represents a constant double number
  */
-case class ConstantExpression private (repr: String) extends Expression
+case class ConstantExpression private[exp] (repr: String) extends Expression
 
 /**
  * Represents compound metrics and their arithmetical(or others) calculations
  */
-case class FunctionExpression private (fnName: String, exprs: Seq[Expression]) extends Expression {
+case class FunctionExpression private[exp] (fnName: String, exprs: Seq[Expression])
+    extends Expression {
   require(exprs.size != 0, "Functions must have at least 1 argument")
 }
 
 /**
  * Represents the leaf metrics
  */
-case class MetricExpression private (metricBuilder: MetricBuilder) extends Expression
+case class MetricExpression private[exp] (metricBuilder: MetricBuilder) extends Expression
 
 /**
  * Represent a histogram expression with specified component, for example the average, or a percentile
  * @param component either a [[HistogramComponent]] or a percentile in Double
  */
-case class HistogramExpression private (
+case class HistogramExpression private[exp] (
   metricBuilder: MetricBuilder,
   component: Either[HistogramComponent, Double])
     extends Expression

util-stats/src/test/scala/com/twitter/finagle/stats/CategorizingExceptionStatsHandlerTest.scala

@@ -1,6 +1,7 @@
 package com.twitter.finagle.stats
 
 import org.scalatest.funsuite.AnyFunSuite
+import scala.collection.compat._
 
 class CategorizingExceptionStatsHandlerTest extends AnyFunSuite {
   val categorizer = (t: Throwable) => { "clienterrors" }
@@ -19,9 +20,9 @@ class CategorizingExceptionStatsHandlerTest extends AnyFunSuite {
 
     val keys = receiver.counters.keys.map(_.mkString("/")).toSeq.sorted
 
-    assert(receiver.counters.filterKeys(_.contains("failures")).size == 0)
+    assert(receiver.counters.view.filterKeys(_.contains("failures")).size == 0)
 
-    assert(receiver.counters.filterKeys(_.contains("clienterrors")).size == 3)
+    assert(receiver.counters.view.filterKeys(_.contains("clienterrors")).size == 3)
     assert(receiver.counters(Seq("clienterrors")) == 1)
     assert(receiver.counters(Seq("clienterrors", classOf[RuntimeException].getName)) == 1)
     assert(
@@ -30,7 +31,7 @@ class CategorizingExceptionStatsHandlerTest extends AnyFunSuite {
       ) == 1
     )
 
-    assert(receiver.counters.filterKeys(_.contains("sourcedfailures")).size == 3)
+    assert(receiver.counters.view.filterKeys(_.contains("sourcedfailures")).size == 3)
     assert(receiver.counters(Seq("sourcedfailures", "service")) == 1)
     assert(
       receiver.counters(Seq("sourcedfailures", "service", classOf[RuntimeException].getName)) == 1
@@ -67,8 +68,8 @@ class CategorizingExceptionStatsHandlerTest extends AnyFunSuite {
 
     val keys = receiver.counters.keys.map(_.mkString("/")).toSeq.sorted
 
-    assert(receiver.counters.filterKeys(_.contains("failures")).size == 3)
-    assert(receiver.counters.filterKeys(_.contains("sourcedfailures")).size == 0)
+    assert(receiver.counters.view.filterKeys(_.contains("failures")).size == 3)
+    assert(receiver.counters.view.filterKeys(_.contains("sourcedfailures")).size == 0)
 
     assert(
       keys == Seq(
@@ -90,17 +91,17 @@ class CategorizingExceptionStatsHandlerTest extends AnyFunSuite {
 
     val keys = receiver.counters.keys.map(_.mkString("/")).toSeq.sorted
 
-    assert(receiver.counters.filterKeys(_.contains("failures")).size == 0)
+    assert(receiver.counters.view.filterKeys(_.contains("failures")).size == 0)
 
-    assert(receiver.counters.filterKeys(_.contains("clienterrors")).size == 2)
+    assert(receiver.counters.view.filterKeys(_.contains("clienterrors")).size == 2)
     assert(receiver.counters(Seq("clienterrors")) == 1)
     assert(
       receiver.counters(
         Seq("clienterrors", classOf[RuntimeException].getName, classOf[Exception].getName)
       ) == 1
     )
 
-    assert(receiver.counters.filterKeys(_.contains("sourcedfailures")).size == 2)
+    assert(receiver.counters.view.filterKeys(_.contains("sourcedfailures")).size == 2)
     assert(receiver.counters(Seq("sourcedfailures", "service")) == 1)
     assert(
       receiver.counters(

util-stats/src/test/scala/com/twitter/finagle/stats/DelegatingStatsReceiverTest.scala

@@ -64,14 +64,14 @@ class DelegatingStatsReceiverTest extends AnyFunSuite with ScalaCheckDrivenPrope
       Gen.oneOf(seq).flatMap(identity)
     }
 
-    implicit val impl = Arbitrary(Gen.delay(statsReceiverTopology(0)))
+    implicit val impl: Arbitrary[StatsReceiver] = Arbitrary(Gen.delay(statsReceiverTopology(0)))
   }
 
   test("DelegatingStatsReceiver.all collects effectively across many StatsReceivers") {
     val ctx = new Ctx
     import ctx._
 
-    forAll { statsReceiver: StatsReceiver =>
+    forAll { (statsReceiver: StatsReceiver) =>
       assert(DelegatingStatsReceiver.all(statsReceiver).size == leafCounter)
       leafCounter = 0
     }

util-stats/src/test/scala/com/twitter/finagle/stats/InMemoryStatsReceiverTest.scala

@@ -58,7 +58,7 @@ class InMemoryStatsReceiverTest extends AnyFunSuite with Eventually with Integra
   test("ReadableGauge.toString") {
     var n = 0
     val stats = new InMemoryStatsReceiver()
-    val g = stats.addGauge("a", "b") { n }
+    val g = stats.addGauge("a", "b") { n.toFloat }
     assert("Gauge(a/b=0.0)" == g.toString)
 
     n = 11

util-stats/src/test/scala/com/twitter/finagle/stats/MultiCategorizingExceptionStatsHandlerTest.scala

@@ -1,6 +1,7 @@
 package com.twitter.finagle.stats
 
 import org.scalatest.funsuite.AnyFunSuite
+import scala.collection.compat._
 
 class MultiCategorizingExceptionStatsHandlerTest extends AnyFunSuite {
   test("uses label, flags, source, exception chain and rolls up") {
@@ -141,8 +142,8 @@ class MultiCategorizingExceptionStatsHandlerTest extends AnyFunSuite {
 
     val keys = receiver.counters.keys.map(_.mkString("/")).toSeq.sorted
 
-    assert(receiver.counters.filterKeys(_.contains("failures")).size == 3)
-    assert(receiver.counters.filterKeys(_.contains("sourcedfailures")).size == 0)
+    assert(receiver.counters.view.filterKeys(_.contains("failures")).size == 3)
+    assert(receiver.counters.view.filterKeys(_.contains("sourcedfailures")).size == 0)
 
     assert(
       keys == Seq(

util-stats/src/test/scala/com/twitter/finagle/stats/exp/ExpressionSchemaTest.scala

@@ -56,7 +56,7 @@ class ExpressionSchemaTest extends AnyFunSuite {
             case NonFatal(exn) =>
               failuresCounter.incr()
           } finally {
-            latencyStat.add(elapsed().inMilliseconds)
+            latencyStat.add(elapsed().inMilliseconds.toFloat)
           }
         }
       }