Add Main class exists rule

src/main/java/org/scijava/maven/plugin/enforcer/MainClassExistsRule.java

@@ -0,0 +1,105 @@
+/*-
+ * #%L
+ * A plugin for managing SciJava-based projects.
+ * %%
+ * Copyright (C) 2014 - 2025 SciJava developers.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+/* ========================================================================
+ * This file was adapted from the no-package-cycles-enforcer-rule project:
+ * https://github.com/andrena/no-package-cycles-enforcer-rule
+ *
+ * Copyright 2013 - 2018 David Burkhart, Ben Romberg, Daniel Galan y Martins,
+ * Bastian Feigl, Marc Philipp, and Carsten Otto.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ======================================================================== */
+
+package org.scijava.maven.plugin.enforcer;
+
+import org.apache.maven.enforcer.rule.api.AbstractEnforcerRule;
+import org.apache.maven.enforcer.rule.api.EnforcerRuleException;
+import org.apache.maven.project.MavenProject;
+
+import javax.inject.Inject;
+import javax.inject.Named;
+import java.io.File;
+import java.util.Objects;
+import java.util.Properties;
+
+/**
+ * Ensures a main class exists if the POM declares one.
+ *
+ * @author Gabriel Selzer
+ */
+@Named("mainClassExistsRule")
+public class MainClassExistsRule extends AbstractEnforcerRule {
+
+    // Inject needed Maven components
+    private final MavenProject project;
+
+    @Inject
+    public MainClassExistsRule(MavenProject project) {
+        this.project = Objects.requireNonNull(project);
+    }
+
+    @Override
+    public void execute() throws EnforcerRuleException {
+        Properties properties = project.getProperties();
+        if (!properties.containsKey("main-class")) {
+            return;
+        }
+        String mainClass = properties.getProperty("main-class");
+        if (mainClass.trim().isEmpty()) {
+            return;
+        }
+
+        // Get the build output directory (e.g., target/classes)
+        String outputDirectory = project.getBuild().getOutputDirectory();
+
+        // Convert class name to file path (e.g., com.example.Main -> com/example/Main.class)
+        String classFilePath = mainClass.replace('.', File.separatorChar) + ".class";
+        // Check if e.g. target/classes/com/example/Main.class exists
+        File classFile = new File(outputDirectory, classFilePath);
+        if (!classFile.exists()) {
+            throw new EnforcerRuleException(
+                "Main class '" + mainClass + "' declared in POM does not exist. " +
+                "Expected to find: " + classFile.getAbsolutePath()
+            );
+        }
+
+        getLog().info("Main class '" + mainClass + "' exists at: " + classFile.getAbsolutePath());
+    }
+}

src/test/java/org/scijava/maven/plugin/enforcer/EnforcerLoggerMock.java

@@ -0,0 +1,92 @@
+/*-
+ * #%L
+ * A plugin for managing SciJava-based projects.
+ * %%
+ * Copyright (C) 2014 - 2025 SciJava developers.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.maven.plugin.enforcer;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Supplier;
+
+import org.apache.maven.enforcer.rule.api.EnforcerLogger;
+
+public class EnforcerLoggerMock implements EnforcerLogger {
+	private final List<String> info = new ArrayList<String>();
+
+	public List<String> getInfo() {
+		return info;
+	}
+
+	public void debug(CharSequence message) {
+	}
+
+	public void debug(Supplier<CharSequence> messageSupplier) {
+	}
+
+	public void info(CharSequence message) {
+		info.add(message.toString());
+	}
+
+	public void info(Supplier<CharSequence> messageSupplier) {
+		info.add(messageSupplier.get().toString());
+	}
+
+	public void warn(CharSequence message) {
+	}
+
+	public void warn(Supplier<CharSequence> messageSupplier) {
+	}
+
+	public void error(CharSequence message) {
+	}
+
+	public void error(Supplier<CharSequence> messageSupplier) {
+	}
+
+	public void warnOrError(CharSequence message) {
+	}
+
+	public void warnOrError(Supplier<CharSequence> messageSupplier) {
+	}
+
+	public boolean isDebugEnabled() {
+		return false;
+	}
+
+	public boolean isInfoEnabled() {
+		return true;
+	}
+
+	public boolean isWarnEnabled() {
+		return false;
+	}
+
+	public boolean isErrorEnabled() {
+		return false;
+	}
+}

src/test/java/org/scijava/maven/plugin/enforcer/MainClassExistsRuleTest.java

@@ -0,0 +1,146 @@
+/*-
+ * #%L
+ * A plugin for managing SciJava-based projects.
+ * %%
+ * Copyright (C) 2014 - 2025 SciJava developers.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package org.scijava.maven.plugin.enforcer;
+
+import org.apache.maven.enforcer.rule.api.EnforcerLogger;
+import org.apache.maven.enforcer.rule.api.EnforcerRuleException;
+import org.apache.maven.model.Build;
+import org.apache.maven.project.MavenProject;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.io.IOException;
+
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Tests for {@link MainClassExistsRule}.
+ *
+ * @author Gabriel Selzer
+ */
+public class MainClassExistsRuleTest {
+
+	/**
+	 * Test subclass that provides a mock logger.
+	 */
+	private class MainClassExistsRuleMock extends MainClassExistsRule {
+		public MainClassExistsRuleMock(MavenProject project) {
+			super(project);
+		}
+
+		@Override
+		public EnforcerLogger getLog() {
+			return logMock;
+		}
+	}
+
+	@Rule
+	public TemporaryFolder temporaryFolder = new TemporaryFolder();
+
+	private MavenProject project;
+	private File outputDirectory;
+	private EnforcerLoggerMock logMock;
+
+	@Before
+	public void setUp() throws Exception {
+		// Create a temporary output directory
+		outputDirectory = temporaryFolder.newFolder("target", "classes");
+
+		// Create a mock MavenProject
+		project = new MavenProject();
+		Build build = new Build();
+		build.setOutputDirectory(outputDirectory.getAbsolutePath());
+		project.setBuild(build);
+
+		// Create a mock logger
+		logMock = new EnforcerLoggerMock();
+	}
+
+	@Test
+	public void TestNoMainClassProperty() throws Exception {
+		// No "main-class" property set
+		MainClassExistsRule rule = new MainClassExistsRuleMock(project);
+        // Execute the rule and make sure it passes
+		rule.execute();
+	}
+
+    @Test
+    public void TestEmptyMainClassProperty() throws Exception {
+        // No "main-class" property set
+        MainClassExistsRule rule = new MainClassExistsRuleMock(project);
+        // Execute the rule and make sure it passes
+        rule.execute();
+    }
+
+	@Test
+	public void TestMainClassExists() throws Exception {
+		// Set main-class property
+		project.getProperties().setProperty("main-class", "com.example.Main");
+
+		// Create the corresponding .class file
+		createClassFile("com.example.Main");
+
+        // Execute the rule and make sure it passes
+		MainClassExistsRule rule = new MainClassExistsRuleMock(project);
+		rule.execute();
+	}
+
+	@Test
+	public void TestMainClassDoesNotExist() {
+		// Set main-class property...
+		project.getProperties().setProperty("main-class", "com.example.NonExistent");
+
+		// ...but don't create the file
+		MainClassExistsRule rule = new MainClassExistsRuleMock(project);
+
+        // ...and assert an Exception is thrown.
+		Assert.assertThrows(EnforcerRuleException.class, rule::execute);
+	}
+
+	/**
+	 * Helper method to create a .class file at the appropriate location
+	 * based on the fully qualified class name.
+	 */
+	private void createClassFile(String fullyQualifiedClassName) throws IOException {
+		String classFilePath = fullyQualifiedClassName.replace('.', File.separatorChar) + ".class";
+		File classFile = new File(outputDirectory, classFilePath);
+
+		// Create parent directories if needed
+		classFile.getParentFile().mkdirs();
+
+		// Create the .class file
+		assertTrue("Failed to create class file: " + classFile.getAbsolutePath(),
+			classFile.createNewFile());
+	}
+}