Add CI check for wrong mima filter directories (#31088)

And fix incorrect filter mima directory for 31055

.github/workflows/binary-compatibility-checks.yml

@@ -38,3 +38,6 @@ jobs:
 
       - name: Report MiMa Binary Issues
         run: sbt -jvm-opts .jvmopts-ci "+~ ${{ matrix.scalaVersion }} mimaReportBinaryIssues"
+
+      - name: Check correct MiMa filter directories
+        run: sbt -jvm-opts .jvmopts-ci checkMimaFilterDirectories

project/MiMa.scala

@@ -18,9 +18,21 @@ object MiMa extends AutoPlugin {
   override def requires = MimaPlugin
   override def trigger = allRequirements
 
+  val checkMimaFilterDirectories =
+    taskKey[Unit]("Check that the mima directories are correct compared to latest version")
+
   override val projectSettings = Seq(
     mimaReportSignatureProblems := true,
-    mimaPreviousArtifacts := akkaPreviousArtifacts(name.value, organization.value, scalaBinaryVersion.value))
+    mimaPreviousArtifacts := akkaPreviousArtifacts(name.value, organization.value, scalaBinaryVersion.value),
+    checkMimaFilterDirectories := checkFilterDirectories(baseDirectory.value))
+
+  def checkFilterDirectories(moduleRoot: File): Unit = {
+    val nextVersionFilterDir = moduleRoot / "src" / "main" / "mima-filters" / s"2.6.${latestPatchOf26 + 1}.backwards.excludes"
+    if (nextVersionFilterDir.exists()) {
+      throw new IllegalArgumentException(s"Incorrect mima filter directory exists: '${nextVersionFilterDir}' " +
+      s"should be with number from current release '${moduleRoot / "src" / "main" / "mima-filters" / s"2.6.${latestPatchOf26}.backwards.excludes"}")
+    }
+  }
 
   def akkaPreviousArtifacts(
       projectName: String,