Fix latest-by-scala-version badge summary to prefer releases

Currently, for the `content-api-firehose-client`, the Scaladex badges page
is showing some contrasting values:

https://index.scala-lang.org/guardian/content-api-firehose-client/badges

* The 'Latest version' badge is showing a good version:
  1.0.12
* The 'JVM badge' (which shows a summary of latest versions by supported
  Scala version, introduced with #660)
  is showing an undesireable pre-release version:
  1.0.13-PREVIEW.rt-dbremove-travis-file.2024-01-10T1738.6e259255

You can see both values on the versions page, but only if you tick the
'Show pre-release versions' button:

* https://index.scala-lang.org/guardian/content-api-firehose-client/artifacts/content-api-firehose-client
* https://index.scala-lang.org/guardian/content-api-firehose-client/artifacts/content-api-firehose-client?pre-releases=true#

modules/core/shared/src/main/scala/scaladex/core/model/SemanticVersion.scala

@@ -103,6 +103,13 @@ object SemanticVersion {
       )
   }
 
+  /**
+   * Often we will prefer the latest release, but if there is no full release, we will select the most recent
+   * pre-release.
+   */
+  val PreferReleases: Ordering[SemanticVersion] =
+    Ordering.by[SemanticVersion, Boolean](_.isRelease).orElse(ordering)
+
   private def MajorP[A: P]: P[Int] = Number
 
   // http://semver.org/#spec-item-10

modules/core/shared/src/test/scala/scaladex/core/model/SemanticVersionTests.scala

@@ -3,6 +3,8 @@ package scaladex.core.model
 import org.scalatest.funspec.AsyncFunSpec
 import org.scalatest.matchers.should.Matchers
 import org.scalatest.prop.TableDrivenPropertyChecks
+import scaladex.core.model.SemanticVersion.PreferReleases
+import scaladex.core.test.Values._
 
 class SemanticVersionTests extends AsyncFunSpec with Matchers with TableDrivenPropertyChecks {
   it("should parse any version") {
@@ -39,6 +41,12 @@ class SemanticVersionTests extends AsyncFunSpec with Matchers with TableDrivenPr
     forAll(inputs)((lower, higher) => lower shouldBe <(higher))
   }
 
+  it("should allow us to prefer releases over pre-releases") {
+    val versions = Seq(`7.0.0`, `7.1.0`, `7.2.0-PREVIEW.1`)
+    versions.max shouldBe `7.2.0-PREVIEW.1`
+    versions.max(PreferReleases) shouldBe `7.1.0`
+  }
+
   it("should encode and decode any version") {
     val inputs = Table[SemanticVersion](
       "semanticVersion",

modules/core/shared/src/test/scala/scaladex/core/test/Values.scala

@@ -36,6 +36,8 @@ object Values {
   val `2.7.0` = PatchVersion(2, 7, 0)
   val `7.0.0` = PatchVersion(7, 0, 0)
   val `7.1.0` = PatchVersion(7, 1, 0)
+  val `7.2.0-PREVIEW.1` = SemanticVersion.parse("7.2.0-PREVIEW.1").get
+  val `7.2.0-PREVIEW.2` = SemanticVersion.parse("7.2.0-PREVIEW.2").get
   val `7.2.0` = PatchVersion(7, 2, 0)
   val `7.3.0` = PatchVersion(7, 3, 0)
 

modules/server/src/main/scala/scaladex/server/route/Badges.scala

@@ -21,6 +21,7 @@ import scaladex.core.model.Scala
 import scaladex.core.model.ScalaJs
 import scaladex.core.model.ScalaNative
 import scaladex.core.model.SemanticVersion
+import scaladex.core.model.SemanticVersion.PreferReleases
 import scaladex.core.service.WebDatabase
 
 class Badges(database: WebDatabase)(implicit executionContext: ExecutionContext) {
@@ -173,7 +174,7 @@ object Badges {
 
   private[route] def summaryOfLatestVersions(versionsByScalaVersions: Map[Scala, Seq[SemanticVersion]]): String =
     versionsByScalaVersions.view
-      .mapValues(_.max)
+      .mapValues(_.max(PreferReleases))
       .groupMap { case (_, latestVersion) => latestVersion } { case (scalaVersion, _) => scalaVersion }
       .toSeq
       .sortBy(_._1)(SemanticVersion.ordering.reverse)

modules/server/src/test/scala/scaladex/server/route/BadgesTests.scala

@@ -9,9 +9,12 @@ import akka.http.scaladsl.model.Uri
 import akka.http.scaladsl.model.headers.Location
 import akka.http.scaladsl.server.Route
 import org.scalatest.BeforeAndAfterAll
+import org.scalatest.funspec.AnyFunSpec
+import org.scalatest.matchers.should.Matchers
 import scaladex.core.model.Scala._
 import scaladex.core.test.Values._
 import scaladex.core.util.ScalaExtensions._
+import scaladex.server.route.Badges.summaryOfLatestVersions
 
 class BadgesTests extends ControllerBaseSuite with BeforeAndAfterAll {
 
@@ -22,17 +25,6 @@ class BadgesTests extends ControllerBaseSuite with BeforeAndAfterAll {
   def insertCats(): Future[Unit] =
     Cats.allArtifacts.map(database.insertArtifact(_, Seq.empty, now)).sequence.map(_ => ())
 
-  it("should provide a concise summary of latest versions") {
-    Badges.summaryOfLatestVersions(
-      Map(
-        `2.11` -> Seq(`7.0.0`, `7.1.0`),
-        `2.12` -> Seq(`7.0.0`, `7.1.0`, `7.2.0`),
-        `2.13` -> Seq(`7.0.0`, `7.1.0`, `7.2.0`, `7.3.0`),
-        `3` -> Seq(`7.2.0`, `7.3.0`)
-      )
-    ) shouldBe "7.3.0 (Scala 3.x, 2.13), 7.2.0 (Scala 2.12), 7.1.0 (Scala 2.11)"
-  }
-
   it("should fallback to JVM artifacts") {
     Get(s"/${Cats.reference}/cats-core/latest-by-scala-version.svg") ~> badgesRoute ~> check {
       status shouldEqual StatusCodes.TemporaryRedirect
@@ -73,3 +65,27 @@ class BadgesTests extends ControllerBaseSuite with BeforeAndAfterAll {
     }
   }
 }
+
+class BadgesUnitTests extends AnyFunSpec with Matchers {
+  it("should provide a concise summary of latest versions") {
+    summaryOfLatestVersions(
+      Map(
+        `2.11` -> Seq(`7.0.0`, `7.1.0`),
+        `2.12` -> Seq(`7.0.0`, `7.1.0`, `7.2.0`),
+        `2.13` -> Seq(`7.0.0`, `7.1.0`, `7.2.0`, `7.3.0`),
+        `3` -> Seq(`7.2.0`, `7.3.0`)
+      )
+    ) shouldBe "7.3.0 (Scala 3.x, 2.13), 7.2.0 (Scala 2.12), 7.1.0 (Scala 2.11)"
+  }
+
+  it("should prefer releases to pre-releases if both are available") {
+    summaryOfLatestVersions(Map(`2.13` -> Seq(`7.0.0`, `7.1.0`, `7.2.0-PREVIEW.1`))) shouldBe "7.1.0 (Scala 2.13)"
+  }
+
+  it("should display latest pre-release if no full release is available") {
+    summaryOfLatestVersions(
+      Map(`2.13` -> Seq(`7.2.0-PREVIEW.1`, `7.2.0-PREVIEW.2`))
+    ) shouldBe s"${`7.2.0-PREVIEW.2`} (Scala 2.13)"
+  }
+
+}