#609 Support application mainClass property as fallback of mainClassName

src/main/groovy/com/github/jengelman/gradle/plugins/shadow/ShadowApplicationPlugin.groovy

@@ -10,6 +10,7 @@ import org.gradle.api.distribution.DistributionContainer
 import org.gradle.api.file.CopySpec
 import org.gradle.api.plugins.ApplicationPlugin
 import org.gradle.api.plugins.ApplicationPluginConvention
+import org.gradle.api.plugins.JavaApplication
 import org.gradle.api.tasks.Sync
 import org.gradle.api.tasks.TaskProvider
 import org.gradle.api.tasks.application.CreateStartScripts
@@ -54,7 +55,7 @@ class ShadowApplicationPlugin implements Plugin<Project> {
     }
 
     protected void configureJarMainClass(Project project) {
-        def classNameProvider = project.provider { project.convention.plugins.application.mainClassName }
+        def classNameProvider = project.provider { getMainClassName() }
         jar.configure { jar ->
             jar.inputs.property('mainClassName', classNameProvider)
             jar.doFirst {
@@ -63,6 +64,15 @@ class ShadowApplicationPlugin implements Plugin<Project> {
         }
     }
 
+    private Object getMainClassName() {
+        def mainClassName = project.convention.plugins.application.mainClassName
+        if (Objects.nonNull(mainClassName)) {
+            return mainClassName
+        }
+
+        return project.extensions.getByType(JavaApplication.class).mainClass.get()
+    }
+
     protected void addRunTask(Project project) {
         ApplicationPluginConvention pluginConvention = (
                 ApplicationPluginConvention) project.convention.plugins.application

src/test/groovy/com/github/jengelman/gradle/plugins/shadow/ShadowPluginSpec.groovy

@@ -1205,6 +1205,48 @@ class ShadowPluginSpec extends PluginSpecification {
         assert result.output.contains('TestApp: Hello World! (foo)')
     }
 
+    @Issue("https://github.com/johnrengelman/shadow/issues/609")
+    def "doesn't error when using application mainClass property"() {
+        given:
+        buildFile.text = defaultBuildScript
+
+        buildFile << """
+            project.ext {
+                aspectjVersion = '1.8.12'
+            }
+
+            apply plugin: 'application'
+
+            application {
+                mainClass.set('myapp.Main')
+            }
+
+            repositories {
+                jcenter()
+            }
+
+            runShadow {
+               args 'foo'
+            }
+
+        """
+
+        file('src/main/java/myapp/Main.java') << """
+            package myapp;
+            public class Main {
+               public static void main(String[] args) {
+                   System.out.println("TestApp: Hello World! (" + args[0] + ")");
+               }
+            }
+        """.stripIndent()
+
+        when:
+        BuildResult result = runner.withArguments('runShadow', '--stacktrace').build()
+
+        then: 'tests that runShadow executed and exited'
+        assert result.output.contains('TestApp: Hello World! (foo)')
+    }
+
     private String escapedPath(File file) {
         file.path.replaceAll('\\\\', '\\\\\\\\')
     }