Avoid running resolve logic with no transport version name (elastic#135379) (elastic#135480)

When resolving transport version conflicts we must lookup the definition
that is being added by the current branch. We do this by detecting the
resource file that has been added. When no files are added, we should
not do anything. This commit moves the logic that detects branches
closer to where it is needed so that we don't possibly run it with an
empty transport version name.

Author: rjernst

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

@@ -87,4 +87,13 @@ class ResolveTransportVersionConflictFuncTest extends AbstractTransportVersionFu
         assertUpperBound("9.1", "new_tv,8012002")
         assertUpperBound("8.19", "new_tv,7123002")
     }
+
+    def "no new transport version is idempotent"() {
+        when:
+        def result = runResolveAndValidateTask().build()
+
+        then:
+        assertResolveAndValidateSuccess(result)
+        assertUpperBound("9.2", "existing_92,8123000")
+    }
 }

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

@@ -428,7 +428,7 @@ class TransportVersionGenerationFuncTest extends AbstractTransportVersionFuncTes
 
     def "upper bounds files must exist for backport branches"() {
         when:
-        def result = runGenerateTask("--backport-branches=9.1,8.13,7.17,6.0").buildAndFail()
+        def result = runGenerateTask("--name", "new_tv", "--backport-branches=9.1,8.13,7.17,6.0").buildAndFail()
 
         then:
         assertGenerateFailure(result, "Missing upper bounds files for branches [6.0, 7.17, 8.13], known branches are [8.19, 9.0, 9.1, 9.2]")

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

@@ -98,14 +98,14 @@ public void run() throws IOException {
         List<String> changedDefinitionNames = resources.getChangedReferableDefinitionNames();
         String targetDefinitionName = getTargetDefinitionName(resources, referencedNames, changedDefinitionNames);
 
-        List<TransportVersionUpperBound> upstreamUpperBounds = resources.getUpperBoundsFromUpstream();
-        Set<String> targetUpperBoundNames = getTargetUpperBoundNames(resources, upstreamUpperBounds, targetDefinitionName);
-
         getLogger().lifecycle("Generating transport version name: " + targetDefinitionName);
         if (targetDefinitionName.isEmpty()) {
             // TODO: resetting upper bounds needs to be done locally, otherwise it pulls in some (incomplete) changes from upstream main
             // resetAllUpperBounds(resources);
         } else {
+            List<TransportVersionUpperBound> upstreamUpperBounds = resources.getUpperBoundsFromUpstream();
+            Set<String> targetUpperBoundNames = getTargetUpperBoundNames(resources, upstreamUpperBounds, targetDefinitionName);
+
             List<TransportVersionId> ids = updateUpperBounds(resources, upstreamUpperBounds, targetUpperBoundNames, targetDefinitionName);
             // (Re)write the definition file.
             resources.writeDefinition(new TransportVersionDefinition(targetDefinitionName, ids, true));