Warning cleanup (#600)

* Remove Unicode arrows (deprecated in Scala 2.13)

Reference:
scala/scala#7540

* Linter: Fix unused config parameter

SuperSafe: Remove usage of .equals
Scalafix: remove unused imports & private hex function

There is no need to guard against LHS null in Scala equality and isInstanceOf

* Remove some hidden typos

* Bump legacy Scala to 2.12.8

* Enable TLS security in README, bump shields to Scala 2.13

README.md

@@ -1,7 +1,7 @@
 # Kamon<img align="right" src="https://rawgit.com/kamon-io/Kamon/master/kamon-logo.svg" height="150px" style="padding-left: 20px"/>
 [![Build Status](https://travis-ci.org/kamon-io/Kamon.svg?branch=master)](https://travis-ci.org/kamon-io/Kamon)
 [![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/kamon-io/Kamon?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
-[![Maven Central](https://maven-badges.herokuapp.com/maven-central/io.kamon/kamon-core_2.12/badge.svg)](https://maven-badges.herokuapp.com/maven-central/io.kamon/kamon-core_2.12)
+[![Maven Central](https://maven-badges.herokuapp.com/maven-central/io.kamon/kamon-core_2.13/badge.svg)](https://maven-badges.herokuapp.com/maven-central/io.kamon/kamon-core_2.13)
 
 Kamon is a set of tools for instrumenting applications running on the JVM. The best way to get started is to go to our
 official [Get Started Page](https://kamon.io/get-started/) and start instrumenting your applications right away! There
@@ -12,7 +12,7 @@ you will also find guides and reference documentation for the core APIs, instrum
 
 This software is licensed under the Apache 2 license, quoted below.
 
-Copyright © 2013-2019 the kamon project <http://kamon.io>
+Copyright © 2013-2019 the kamon project <https://kamon.io/>
 
 Licensed under the Apache License, Version 2.0 (the "License"); you may not
 use this file except in compliance with the License. You may obtain a copy of

build.sbt

@@ -136,7 +136,7 @@ lazy val commonSettings = Seq(
   startYear := Some(2013),
   concurrentRestrictions in Global += Tags.limit(Tags.Test, 1),
   scalaVersion := "2.13.0",
-  crossScalaVersions := Seq("2.11.12", "2.12.7", "2.13.0"),
+  crossScalaVersions := Seq("2.11.12", "2.12.8", "2.13.0"),
   scalacOptions ++= Seq(
     "-deprecation",
     "-encoding", "UTF-8",

kamon-core/src/main/scala/kamon/ContextPropagation.scala

@@ -63,7 +63,7 @@ trait ContextPropagation { self: Configuration =>
     _defaultBinaryPropagation
 
   private def init(config: Config): Unit = synchronized {
-    _propagationComponents = ContextPropagation.Channels.from(self.config)
+    _propagationComponents = ContextPropagation.Channels.from(config)
     _defaultHttpPropagation = _propagationComponents.httpChannels(ContextPropagation.DefaultHttpChannel)
     _defaultBinaryPropagation = _propagationComponents.binaryChannels(ContextPropagation.DefaultBinaryChannel)
   }

kamon-core/src/main/scala/kamon/ContextStorage.scala

@@ -141,7 +141,7 @@ object ContextStorage {
     * instrumentation follows them around.
     */
   private val _contextStorage: Storage = {
-    if("true".equals(System.getProperty("kamon.context.debug")))
+    if(sys.props("kamon.context.debug") == "true")
       Storage.Debug()
     else
       Storage.ThreadLocal()

kamon-core/src/main/scala/kamon/context/BinaryPropagation.scala

@@ -28,7 +28,7 @@ import org.slf4j.LoggerFactory
 
 import scala.reflect.ClassTag
 import scala.util.control.NonFatal
-import scala.util.{Failure, Success, Try}
+import scala.util.Try
 
 
 /**

kamon-core/src/main/scala/kamon/context/HttpPropagation.scala

@@ -24,7 +24,6 @@ import org.slf4j.LoggerFactory
 
 import scala.reflect.ClassTag
 import scala.util.control.NonFatal
-import scala.util.{Failure, Success}
 
 /**
   * Context propagation that uses HTTP headers as the transport medium. HTTP propagation mechanisms read any number of
@@ -169,33 +168,30 @@ object HttpPropagation {
 
     private val _longTypePrefix = "l:"
     private val _booleanTypePrefix = "b:"
-    private val _booleanTrue = "true"
-    private val _booleanFalse = "false"
 
     /**
       * Tries to infer and parse a value into one of the supported tag types: String, Long or Boolean by looking for the
       * type indicator prefix on the tag value. If the inference fails it will default to treat the value as a String.
       */
     private def parseTagValue(value: String): Any = {
-      if (value.isEmpty || value.length < 2) // Empty and short values definitely do not have type indicators.
+      if (value.length < 2) // Empty and short values definitely do not have type indicators.
         value
       else {
         if(value.startsWith(_longTypePrefix)) {
           // Try to parse the content as a Long value.
           val remaining = value.substring(2)
           try {
-            java.lang.Long.parseLong(remaining)
+            remaining.toLong
           } catch {
-            case _: Throwable => remaining
+            case _: java.lang.NumberFormatException => remaining
           }
 
         } else if(value.startsWith(_booleanTypePrefix)) {
-
           // Try to parse the content as a Boolean value.
           val remaining = value.substring(2)
-          if(remaining.equals(_booleanTrue))
+          if(remaining == "true")
             true
-          else if(remaining.equals(_booleanFalse))
+          else if(remaining == "false")
             false
           else
             remaining

kamon-core/src/main/scala/kamon/metric/Histogram.scala

@@ -17,11 +17,10 @@
 package kamon.metric
 
 import java.nio.ByteBuffer
-import java.time.Duration
 
 import kamon.metric.Metric.{BaseMetric, BaseMetricAutoUpdate}
 import kamon.tag.TagSet
-import org.HdrHistogram.{BaseAtomicHdrHistogram, BaseLocalHdrHistogram, HdrHistogramInternalState, ZigZag}
+import org.HdrHistogram.{BaseAtomicHdrHistogram, HdrHistogramInternalState, ZigZag}
 import org.slf4j.LoggerFactory
 
 
@@ -71,7 +70,7 @@ object Histogram {
           _logger.warn (
             s"Failed to record value [$value] on [${metric.name},${tags}] because the value is outside of the " +
             s"configured range. The recorded value was adjusted to the highest trackable value [$highestTrackableValue]. " +
-            s"You might need to change your dynamic range configuration for this metric"
+            "You might need to change your dynamic range configuration for this metric"
           )
       }
 
@@ -89,7 +88,7 @@ object Histogram {
           _logger.warn (
             s"Failed to record value [$value] on [${metric.name},${tags}] because the value is outside of the " +
             s"configured range. The recorded value was adjusted to the highest trackable value [$highestTrackableValue]. " +
-            s"You might need to change your dynamic range configuration for this metric"
+            "You might need to change your dynamic range configuration for this metric"
           )
       }
 

kamon-core/src/main/scala/kamon/metric/MeasurementUnit.scala

@@ -78,7 +78,7 @@ object MeasurementUnit {
       value
     } else if(from == to)
       value
-    else (from.magnitude.scaleFactor / to.magnitude.scaleFactor) * value.toDouble
+    else (from.magnitude.scaleFactor / to.magnitude.scaleFactor) * value
   }
 
   /**

kamon-core/src/main/scala/kamon/metric/MetricRegistry.scala

@@ -134,19 +134,19 @@ class MetricRegistry(config: Config, scheduler: ScheduledExecutorService, clock:
       sys.error(s"Cannot redefine metric [$name] as a [${instrumentType.name}], it was already registered as a [${metric.getClass.getName}]")
 
   private def checkDescription(name: String, description: String, providedDescription: Option[String]): Unit =
-    if(providedDescription.filter(d => d != description).nonEmpty)
+    if(providedDescription.exists(d => d != description))
       _logger.warn(s"Ignoring new description [${providedDescription.getOrElse("")}] for metric [${name}]")
 
   private def checkUnit(name: String, unit: MeasurementUnit, providedUnit: Option[MeasurementUnit]): Unit =
-    if(providedUnit.filter(u => u != unit).nonEmpty)
+    if(providedUnit.exists(u => u != unit))
       _logger.warn(s"Ignoring new unit [${providedUnit.getOrElse("")}] for metric [${name}]")
 
   private def checkAutoUpdate(name: String, autoUpdateInterval: Duration, providedAutoUpdateInterval: Option[Duration]): Unit =
-    if(providedAutoUpdateInterval.filter(u => u != autoUpdateInterval).nonEmpty)
+    if(providedAutoUpdateInterval.exists(u => u != autoUpdateInterval))
       _logger.warn(s"Ignoring new auto-update interval [${providedAutoUpdateInterval.getOrElse("")}] for metric [${name}]")
 
   private def checkDynamicRange(name: String, dynamicRange: DynamicRange, providedDynamicRange: Option[DynamicRange]): Unit =
-    if(providedDynamicRange.filter(dr => dr != dynamicRange).nonEmpty)
+    if(providedDynamicRange.exists(dr => dr != dynamicRange))
       _logger.warn(s"Ignoring new dynamic range [${providedDynamicRange.getOrElse("")}] for metric [${name}]")
 
 

kamon-core/src/main/scala/kamon/metric/PeriodSnapshot.scala

@@ -135,7 +135,7 @@ object PeriodSnapshot {
     }
 
     private def isSameDurationAsTickInterval(): Boolean = {
-      Kamon.config().getDuration("kamon.metric.tick-interval").equals(period)
+      Kamon.config().getDuration("kamon.metric.tick-interval") == period
     }
 
     private def buildPeriodSnapshot(from: Instant, to: Instant, resetState: Boolean): PeriodSnapshot = {

kamon-core/src/main/scala/kamon/metric/RangeSampler.scala

@@ -134,7 +134,7 @@ object RangeSampler {
         case _: ArrayIndexOutOfBoundsException =>
           _logger.warn (
             s"Failed to record value on [${metric.name},${tags}] because the value is outside of the " +
-            s"configured range. You might need to change your dynamic range configuration for this metric"
+            "configured range. You might need to change your dynamic range configuration for this metric"
           )
       }
 

kamon-core/src/main/scala/kamon/metric/Timer.scala

@@ -106,7 +106,7 @@ object Timer {
           _logger.warn (
             s"Failed to record value [$nanos] on [${metric.name},${tags}] because the value is outside of the " +
             s"configured range. The recorded value was adjusted to the highest trackable value [$highestTrackableValue]. " +
-            s"You might need to change your dynamic range configuration for this metric"
+            "You might need to change your dynamic range configuration for this metric"
           )
       }
 

kamon-core/src/main/scala/kamon/module/ModuleRegistry.scala

@@ -105,7 +105,7 @@ class ModuleRegistry(configuration: Configuration, clock: Clock, metricRegistry:
     }
 
     // Remove all modules that no longer exist in the configuration.
-    val missingModules = automaticallyRegisteredModules.filterKeys(moduleName => configuredModules.find(_.name == moduleName).isEmpty)
+    val missingModules = automaticallyRegisteredModules.filterKeys(moduleName => !configuredModules.exists(_.name == moduleName))
     missingModules.foreach {
       case (_, entry) => stopModule(entry)
     }

kamon-core/src/main/scala/kamon/package.scala

@@ -58,13 +58,13 @@ package object kamon {
     */
   implicit class AtomicGetOrElseUpdateOnTrieMap[K, V](val trieMap: TrieMap[K, V]) extends AnyVal {
 
-    def atomicGetOrElseUpdate(key: K, op: ⇒ V): V =
-      atomicGetOrElseUpdate(key, op, { _: V ⇒ () }, { _: V ⇒ () })
+    def atomicGetOrElseUpdate(key: K, op: => V): V =
+      atomicGetOrElseUpdate(key, op, { _: V => () }, { _: V => () })
 
-    def atomicGetOrElseUpdate(key: K, op: ⇒ V, cleanup: V ⇒ Unit, init: V => Unit): V =
+    def atomicGetOrElseUpdate(key: K, op: => V, cleanup: V => Unit, init: V => Unit): V =
       trieMap.get(key) match {
-        case Some(v) ⇒ v
-        case None ⇒
+        case Some(v) => v
+        case None =>
           val d = op
           trieMap.putIfAbsent(key, d) match {
             case Some(oldValue) =>

kamon-core/src/main/scala/kamon/tag/Lookups.scala

@@ -169,16 +169,16 @@ object Lookups {
   private val _plainString = (a: String) => a
   private val _stringOption = (a: String) => Option(a)
   private val _stringOptional = (a: String) => Optional.of(a)
-  private val _stringSafetyCheck = (a: Any) => a != null && a.isInstanceOf[String]
+  private val _stringSafetyCheck = (a: Any) => a.isInstanceOf[String]
 
   private val _plainLong = (a: java.lang.Long) => a
   private val _longOption = (a: Long) => Option(a)
   private val _longOptional = (a: Long) => Optional.of(a)
-  private val _longSafetyCheck = (a: Any) => a != null && a.isInstanceOf[Long]
+  private val _longSafetyCheck = (a: Any) => a.isInstanceOf[Long]
 
   private val _plainBoolean = (a: java.lang.Boolean) => a
   private val _booleanOption = (a: Boolean) => Option(a)
   private val _booleanOptional = (a: Boolean) => Optional.of(a)
-  private val _booleanSafetyCheck = (a: Any) => a != null && a.isInstanceOf[Boolean]
+  private val _booleanSafetyCheck = (a: Any) => a.isInstanceOf[Boolean]
 
 }

kamon-core/src/main/scala/kamon/util/Clock.scala

@@ -106,7 +106,7 @@ object Clock {
       _systemClock.getZone()
 
     override def nanosSince(instant: Instant): Long = {
-      return nanosBetween(instant, this.instant())
+      nanosBetween(instant, this.instant())
     }
   }
 
@@ -116,7 +116,7 @@ object Clock {
   def nanosBetween(left: Instant, right: Instant): Long = {
     val secsDiff = Math.subtractExact(right.getEpochSecond, left.getEpochSecond)
     val totalNanos = Math.multiplyExact(secsDiff, _nanosInSecond)
-    return Math.addExact(totalNanos, right.getNano - left.getNano)
+    Math.addExact(totalNanos, right.getNano - left.getNano)
   }
 
   /**

kamon-core/src/main/scala/kamon/util/DynamicAccess.scala

@@ -50,7 +50,7 @@ class DynamicAccess(val classLoader: ClassLoader) {
       val obj = constructor.newInstance(values: _*)
       val t = implicitly[ClassTag[T]].runtimeClass
       if (t.isInstance(obj)) obj.asInstanceOf[T] else throw new ClassCastException(clazz.getName + " is not a subtype of " + t)
-    } catch { case i: InvocationTargetException if i.getTargetException ne null ⇒ throw i.getTargetException }
+    } catch { case i: InvocationTargetException if i.getTargetException ne null => throw i.getTargetException }
 
   /**
     * Tries to create an instance of the provided fully-qualified class name, passing the provided arguments to the

kamon-core/src/main/scala/kamon/util/Filter.scala

@@ -181,8 +181,8 @@ object Filter {
     private val _pathRegex = pattern.r
 
     override def accept(value: String): Boolean = value match {
-      case _pathRegex(_*) ⇒ true
-      case _              ⇒ false
+      case _pathRegex(_*) => true
+      case _              => false
     }
   }
 

kamon-core/src/main/scala/kamon/util/HexCodec.scala

@@ -56,20 +56,6 @@ object HexCodec {
     result
   }
 
-  /**
-    * Returns 16 or 32 character hex string depending on if {@code high} is zero.
-    */
-  private def toLowerHex(high: Long, low: Long): String = {
-    val result = new Array[Char](if (high != 0) 32 else 16)
-    var pos = 0
-    if (high != 0) {
-      writeHexLong(result, pos, high)
-      pos += 16
-    }
-    writeHexLong(result, pos, low)
-    new String(result)
-  }
-
   /**
     * Inspired by {@code okio.Buffer.writeLong}
     */

kamon-testkit/src/main/scala/kamon/testkit/MetricInspection.scala

@@ -58,7 +58,7 @@ object MetricInspection {
   def instruments[Inst <: Instrument[Inst, Sett], Sett <: Metric.Settings](metric: Metric[Inst, Sett], tags: TagSet): Map[TagSet, Inst] = {
     def hasAllRequestedTags(instrumentTags: TagSet): Boolean = {
       val instrumentPairs = instrumentTags.iterator().map(t => (t.key -> Tag.unwrapValue(t))).toMap
-      tags.iterator().forall(t => instrumentPairs.get(t.key).filter(sv => sv == Tag.unwrapValue(t)).nonEmpty)
+      tags.iterator().forall(t => instrumentPairs.get(t.key).exists(sv => sv == Tag.unwrapValue(t)))
     }
 
     instrumentsMap(metric)