Make all older Scala versions work

Previously, we cross published 2.12.13 and for older versions we used 2.12.12 due to changes to compiler API. This however did not work for the sbt plugin, which had the coursier resolve a wrong version for a transitive dependency. Now, we are using a more base reporting API, which should work for both 2.12.12- and 2.12.13+ versions. I previously haven't noticed that this is possible.

The couriser issue is coursier/coursier#1950

.github/workflows/ci.yml

@@ -28,6 +28,7 @@ jobs:
         java: [[email protected], [email protected]]
         command:
           - "'++2.11.12 test'"
+          - "'++2.12.12 test'"
           - "'++2.12.13 test' scripted"
           - "'++2.13.4 test'"
           - "'++3.0.0-M3 test'"

build.sbt

@@ -1,8 +1,6 @@
-import sbt.librarymanagement.CrossVersion
 import scala.collection.mutable
 
 def scala212 = "2.12.13"
-def scala212Legacy = "2.12.12"
 def scala211 = "2.11.12"
 def scala213 = "2.13.4"
 def scala3 = List("3.0.0-RC1", "3.0.0-M3", "3.0.0-M2")
@@ -68,7 +66,7 @@ def crossSetting[A](
 inThisBuild(
   List(
     scalaVersion := scala212,
-    crossScalaVersions := List(scala212, scala212Legacy, scala211, scala213) ::: scala3,
+    crossScalaVersions := List(scala212, scala211, scala213) ::: scala3,
     organization := "org.scalameta",
     licenses := Seq(
       "Apache-2.0" -> url("http://www.apache.org/licenses/LICENSE-2.0")
@@ -118,13 +116,6 @@ val V = new {
   val scalacheck = "1.15.2"
 }
 
-val crossVersionLegacy = Def.setting {
-  CrossVersion.binaryWith(
-    prefix = "",
-    suffix = if (scalaVersion.value == scala212Legacy) ".12" else ""
-  )
-}
-
 lazy val pprintVersion = Def.setting {
   if (scalaVersion.value.startsWith("2.11")) "0.5.4"
   else "0.6.0"
@@ -163,7 +154,6 @@ lazy val runtime = project
     sharedSettings,
     moduleName := "mdoc-runtime",
     unmanagedSourceDirectories.in(Compile) ++= multiScalaDirectories("runtime").value,
-    crossVersion := crossVersionLegacy.value,
     libraryDependencies ++= crossSetting(
       scalaVersion.value,
       if2 = List(
@@ -184,7 +174,6 @@ lazy val mdoc = project
   .settings(
     sharedSettings,
     unmanagedSourceDirectories.in(Compile) ++= multiScalaDirectories("mdoc").value,
-    crossVersion := crossVersionLegacy.value,
     moduleName := "mdoc",
     mainClass in assembly := Some("mdoc.Main"),
     assemblyJarName in assembly := "mdoc.jar",
@@ -342,7 +331,6 @@ lazy val plugin = project
         managedResourceDirectories.in(Compile).value.head / "sbt-mdoc.properties"
       val props = new java.util.Properties()
       props.put("version", version.value)
-      props.put("scala212Legacy", scala212Legacy)
       IO.write(props, "sbt-mdoc properties", out)
       List(out)
     },
@@ -366,7 +354,6 @@ lazy val js = project
   .in(file("mdoc-js"))
   .settings(
     sharedSettings,
-    crossVersion := crossVersionLegacy.value,
     crossScalaVersions --= scala3,
     moduleName := "mdoc-js",
     libraryDependencies ++=

mdoc-sbt/src/main/scala/mdoc/BuildInfo.scala

@@ -5,7 +5,6 @@ import java.util.Properties
 object BuildInfo {
   def version: String =
     props.getProperty("version", "0.8.0-SNAPSHOT")
-  def scala212Legacy: String = props.getProperty("scala212Legacy", "2.12.12")
 
   private lazy val props: Properties = {
     val props = new Properties()

mdoc-sbt/src/main/scala/mdoc/MdocPlugin.scala

@@ -66,13 +66,6 @@ object MdocPlugin extends AutoPlugin {
     }
   }
 
-  def compatibleScalaVersion = Def.setting {
-    scalaVersion.value.takeWhile(_ != '-').split('.').take(3).map(_.toInt) match {
-      case Array(2, 12, minor) if minor <= 12 => BuildInfo.scala212Legacy
-      case _ => scalaBinaryVersion.value
-    }
-  }
-
   override def projectSettings: Seq[Def.Setting[_]] =
     List(
       mdocIn := baseDirectory.in(ThisBuild).value / "docs",
@@ -98,9 +91,7 @@ object MdocPlugin extends AutoPlugin {
         val isJS = mdocJS.value.isDefined
         if (mdocAutoDependency.value) {
           val suffix = if (isJS) "-js" else ""
-          List(
-            "org.scalameta" % s"mdoc${suffix}_${compatibleScalaVersion.value}" % BuildInfo.version
-          )
+          List("org.scalameta" %% s"mdoc$suffix" % BuildInfo.version)
         } else {
           List()
         }

mdoc/src/main/scala-2.12/mdoc/internal/markdown/VersionSpecificFilteringReporter.scala

@@ -0,0 +1,18 @@
+package mdoc.internal.markdown
+
+import scala.tools.nsc.Settings
+import scala.tools.nsc.reporters.Reporter
+import scala.reflect.internal.util.Position
+import scala.reflect.internal.util.NoPosition
+
+trait VersionSpecificFilteringReporter extends Reporter { self: FilterStoreReporter =>
+  override def info0(pos: Position, msg: String, severity: Severity, force: Boolean): Unit = {
+    if (!infos.exists(info => pos != NoPosition && info.pos.point == pos.point))
+      add(pos, msg, severity)
+  }
+
+  override def hasErrors: Boolean = infos.exists(_.severity == ERROR)
+
+  override def hasWarnings: Boolean = infos.exists(_.severity == WARNING)
+
+}