[9.0] Only validate upper bound of current branch on release branches (#135391)

build-tools-internal/src/integTest/groovy/org/elasticsearch/gradle/internal/transport/TransportVersionValidationFuncTest.groovy

@@ -294,4 +294,21 @@ class TransportVersionValidationFuncTest extends AbstractTransportVersionFuncTes
         then:
         result.task(":myserver:validateTransportVersionResources").outcome == TaskOutcome.SUCCESS
     }
+
+    def "only current upper bound validated on release branch"() {
+        given:
+        file("myserver/build.gradle") << """
+            tasks.named('validateTransportVersionResources') {
+                currentUpperBoundName = '9.0'
+            }
+        """
+        referableAndReferencedTransportVersion("some_tv", "8124000,8012004")
+        transportVersionUpperBound("9.1", "some_tv", "8012004")
+
+        when:
+        def result = gradleRunner("validateTransportVersionResources").build()
+
+        then:
+        result.task(":myserver:validateTransportVersionResources").outcome == TaskOutcome.SUCCESS
+    }
 }

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/transport/ValidateTransportVersionResourcesTask.java

@@ -83,6 +83,7 @@ public void validateTransportVersions() throws IOException {
         Map<String, TransportVersionDefinition> allDefinitions = collectAllDefinitions(referableDefinitions, unreferableDefinitions);
         Map<Integer, List<IdAndDefinition>> idsByBase = collectIdsByBase(allDefinitions.values());
         Map<String, TransportVersionUpperBound> upperBounds = resources.getUpperBounds();
+        TransportVersionUpperBound currentUpperBound = upperBounds.get(getCurrentUpperBoundName().get());
         boolean onReleaseBranch = checkIfDefinitelyOnReleaseBranch(upperBounds);
 
         for (var definition : referableDefinitions.values()) {
@@ -94,14 +95,21 @@ public void validateTransportVersions() throws IOException {
         }
 
         for (var entry : idsByBase.entrySet()) {
-            validateBase(entry.getKey(), entry.getValue());
+            int baseId = entry.getKey();
+            // on main we validate all bases, but on release branches we only validate up to the current upper bound
+            if (onReleaseBranch == false || baseId <= currentUpperBound.definitionId().base()) {
+                validateBase(baseId, entry.getValue());
+            }
         }
 
-        for (var upperBound : upperBounds.values()) {
-            validateUpperBound(upperBound, allDefinitions, idsByBase);
-        }
+        if (onReleaseBranch) {
+            // on release branches we only check the current upper bound, others may be inaccurate
+            validateUpperBound(currentUpperBound, allDefinitions, idsByBase);
+        } else {
+            for (var upperBound : upperBounds.values()) {
+                validateUpperBound(upperBound, allDefinitions, idsByBase);
+            }
 
-        if (onReleaseBranch == false) {
             validatePrimaryIds(resources, upperBounds, allDefinitions);
         }
     }