Disable BWC tests against 5.6.17 snapshots

Author: mark-vieira

buildSrc/src/main/java/org/elasticsearch/gradle/VersionCollection.java

@@ -126,6 +126,10 @@ protected VersionCollection(List<String> versionLines, Version currentVersionPro
                 .orElseThrow(() -> new IllegalStateException("Unexpected number of versions in collection"))
         );
 
+        // Previous major branch is dead so ignore the latest version which will never be released
+        Version previousMajorUnreleased = getLatestVersionByKey(this.groupByMajor, currentVersion.getMajor() - 1);
+        groupByMajor.get(currentVersion.getMajor() - 1).remove(previousMajorUnreleased);
+
         assertCurrentVersionMatchesParsed(currentVersionProperty);
 
         assertNoOlderThanTwoMajors();
@@ -206,7 +210,8 @@ public List<Version> getUnreleased() {
         unreleased.add(currentVersion);
 
         // the tip of the previous major is unreleased for sure, be it a minor or a bugfix
-        unreleased.add(getLatestVersionByKey(this.groupByMajor, currentVersion.getMajor() - 1));
+        // The 5.6 release train will have no further releases so don't test against unreleased snapshots
+        // unreleased.add(getLatestVersionByKey(this.groupByMajor, currentVersion.getMajor() - 1));
 
         final Map<Integer, List<Version>> groupByMinor = getReleasedMajorGroupedByMinor();
         int greatestMinor = groupByMinor.keySet().stream().max(Integer::compareTo).orElse(0);

qa/verify-version-constants/build.gradle

@@ -60,8 +60,10 @@ unitTest.enabled = false
 
 task bwcTestSnapshots {
   if (project.bwc_tests_enabled) {
-    final def version = bwcVersions.unreleasedIndexCompatible.first()
-    dependsOn "v${version}#bwcTest"
+    if (bwcVersions.unreleasedIndexCompatible.isEmpty() == false) {
+      final def version = bwcVersions.unreleasedIndexCompatible.first()
+      dependsOn "v${version}#bwcTest"
+    }
   }
 }