Automatically find Maven Home

.github/workflows/java.yml

@@ -23,13 +23,7 @@ jobs:
         java-version: ${{ matrix.java-version }}
         distribution: 'zulu'
         cache: maven
-    - name: Maven Info
-      run:  echo "home=$(mvn -v -q | grep "Maven home:" | sed -e 's/Maven home://' -e 's/^[[:space:]]*//')" >> $GITHUB_OUTPUT
-      shell: bash
-      id: maven
     - run: mvn --batch-mode install
-      env:
-        M2_HOME: '${{ steps.maven.outputs.home }}'
     - name: Test Report
       uses: dorny/test-reporter@v1
       if: success() || failure()

core/src/main/java/com/github/swissquote/carnotzet/core/maven/MavenDependencyResolver.java

@@ -1,5 +1,6 @@
 package com.github.swissquote.carnotzet.core.maven;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.io.Reader;
@@ -24,15 +25,17 @@
 
 import com.github.swissquote.carnotzet.core.CarnotzetDefinitionException;
 import com.github.swissquote.carnotzet.core.CarnotzetModule;
+import com.github.swissquote.carnotzet.core.runtime.DefaultCommandRunner;
 
 import lombok.Getter;
-import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 
 @Slf4j
-@RequiredArgsConstructor
 public class MavenDependencyResolver {
 
+	private static final String MAVEN_HOME_PROPERTY = "maven.home";
+	private static final String M2_HOME = "M2_HOME";
+
 	private final Function<CarnotzetModuleCoordinates, String> moduleNameProvider;
 
 	private final Path resourcesPath;
@@ -42,6 +45,16 @@ public class MavenDependencyResolver {
 	private final ConcurrentHashMap<CarnotzetModuleCoordinates, Node> dependencyTreeCache = new ConcurrentHashMap<>();
 	private Path localRepoPath;
 
+	public MavenDependencyResolver(Function<CarnotzetModuleCoordinates, String> moduleNameProvider, Path resourcesPath) {
+		this.moduleNameProvider = moduleNameProvider;
+		this.resourcesPath = resourcesPath;
+
+		File mavenHome = getMavenHome();
+		if (mavenHome != null) {
+			maven.setMavenHome(mavenHome);
+		}
+	}
+
 	public List<CarnotzetModule> resolve(CarnotzetModuleCoordinates topLevelModuleId, Boolean failOnCycle) {
 		log.debug("Resolving module dependencies");
 		Node tree = getDependenciesTree(topLevelModuleId);
@@ -177,6 +190,42 @@ private void executeMavenBuild(List<String> goals, InvocationOutputHandler outpu
 		}
 	}
 
+	private static boolean isBlank(String str) {
+		return str == null || str.trim().isEmpty();
+	}
+
+	private static File getMavenHome() {
+		if (!isBlank(System.getProperty(MAVEN_HOME_PROPERTY))) {
+			File mavenHome = new File(System.getProperty(MAVEN_HOME_PROPERTY));
+			if (mavenHome.exists()) {
+				return mavenHome;
+			}
+		}
+		if (!isBlank(System.getenv(M2_HOME))) {
+			File mavenHome = new File(System.getenv(M2_HOME));
+			if (mavenHome.exists()) {
+				return mavenHome;
+			}
+		}
+
+		// Get it directly from maven
+		String out = DefaultCommandRunner.INSTANCE.runCommandAndCaptureOutput("mvn", "help:evaluate", "-Dexpression=maven.home");
+		String[] lines = out.split("\\R");
+		for (String line : lines) {
+			if (line.contains("INFO")) {
+				continue;
+			}
+
+			File mavenHome = new File(line.trim());
+			if (mavenHome.exists()) {
+				return mavenHome;
+			}
+		}
+
+		log.warn("Could not find a maven home in {} or {} or by calling mvn", MAVEN_HOME_PROPERTY, M2_HOME);
+		return null;
+	}
+
 	/**
 	 * Relies on mvn dependency:tree -Dverbose to get a full dependency tree, including omitted ones.
 	 * This uses maven 2 and may be inconsistent with maven 3 resolved dependencies.

core/src/test/java/com/github/swissquote/carnotzet/core/maven/MavenDependencyResolverTest.java

@@ -0,0 +1,43 @@
+package com.github.swissquote.carnotzet.core.maven;
+
+import static org.junit.Assert.assertEquals;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.function.Function;
+import java.util.regex.Pattern;
+
+import org.junit.Ignore;
+import org.junit.Test;
+
+import com.github.swissquote.carnotzet.core.Carnotzet;
+import com.github.swissquote.carnotzet.core.CarnotzetConfig;
+import com.github.swissquote.carnotzet.core.CarnotzetModule;
+
+public class MavenDependencyResolverTest {
+
+	private Function<CarnotzetModuleCoordinates, String>  getDefaultModuleResolver() {
+		Pattern moduleFilterPattern = Pattern.compile(CarnotzetConfig.DEFAULT_MODULE_FILTER_PATTERN);
+		Pattern classifierIncludePattern = Pattern.compile(CarnotzetConfig.DEFAULT_CLASSIFIER_INCLUDE_PATTERN);
+
+		return (module) -> Carnotzet.getModuleName(module, moduleFilterPattern, classifierIncludePattern);
+	}
+
+	@Test
+	@Ignore("Dependencies are not published to Maven Central which makes it impossible to run this test in CI for now")
+	public void resolveDependencies() {
+		Path resourcesPath = Paths.get("/tmp/carnotzet_" + System.nanoTime());
+
+		MavenDependencyResolver resolver = new MavenDependencyResolver(
+				getDefaultModuleResolver(),
+				resourcesPath.resolve("maven")
+		);
+
+		CarnotzetModuleCoordinates coord = new CarnotzetModuleCoordinates("com.github.swissquote.examples", "voting-all-carnotzet", "1.8.9-SNAPSHOT", null);
+
+		List<CarnotzetModule> modules = resolver.resolve(coord, true);
+
+		assertEquals(modules.size(), 6);
+	}
+}