improvement: checkExplicitSourceCompatabilityTask ignores projects without java source

changelog/@unreleased/pr-1584.v2.yml

@@ -0,0 +1,6 @@
+type: improvement
+improvement:
+  description: checkExplicitSourceCompatabilityTask ignores projects without java
+    source
+  links:
+  - https://github.com/palantir/gradle-baseline/pull/1584

gradle-baseline-java/src/main/groovy/com/palantir/baseline/tasks/CheckExplicitSourceCompatibilityTask.java

@@ -31,6 +31,7 @@
 import org.gradle.api.provider.Property;
 import org.gradle.api.publish.PublishingExtension;
 import org.gradle.api.specs.Spec;
+import org.gradle.api.tasks.SourceSetContainer;
 import org.gradle.api.tasks.TaskAction;
 import org.gradle.api.tasks.options.Option;
 import org.gradle.util.GradleVersion;
@@ -74,6 +75,14 @@ public boolean isSatisfiedBy(Task element) {
                 return !publishing.getPublications().isEmpty();
             }
         });
+        onlyIf(new Spec<Task>() {
+            @Override
+            public boolean isSatisfiedBy(Task task) {
+                return getProject().getExtensions().getByType(SourceSetContainer.class).stream()
+                        .anyMatch(
+                                sourceSet -> !sourceSet.getAllJava().getFiles().isEmpty());
+            }
+        });
     }
 
     @Option(option = "fix", description = "Whether to apply the suggested fix to build.gradle")

gradle-baseline-java/src/test/groovy/com/palantir/baseline/plugins/BaselineReproducibilityIntegrationSpec.groovy

@@ -69,7 +69,7 @@ class BaselineReproducibilityIntegrationSpec extends IntegrationSpec {
         writeHelloWorld()
 
         then:
-        runTasksSuccessfully("checkExplicitSourceCompatibility")
+        def result = runTasksSuccessfully("checkExplicitSourceCompatibility")
     }
 
     def 'no-op if nothing is published'() {
@@ -87,4 +87,26 @@ class BaselineReproducibilityIntegrationSpec extends IntegrationSpec {
         def output = runTasksSuccessfully("check")
         output.getStandardOutput().contains("> Task :checkExplicitSourceCompatibility SKIPPED")
     }
+
+    def 'no-op if there is not source'() {
+        when:
+        buildFile << """
+        ${applyPlugin(BaselineReproducibility.class)}
+        apply plugin: 'java'
+        apply plugin: 'maven-publish'
+        version '1.2.3'
+
+        publishing {
+            publications {
+                maven(MavenPublication) {
+                    from components.java
+                }
+            }
+        }
+        """.stripIndent()
+
+        then:
+        def output = runTasksSuccessfully("check")
+        output.getStandardOutput().contains("> Task :checkExplicitSourceCompatibility SKIPPED")
+    }
 }