Do not automatically detect JVMs on CI systems

Automatic detection on CI systems can cause a lot of trouble (e.g.
memory consumption, time to read the jvms, old jvms lingering around)
and is generally not useful as a CI has usually a dedicated and fixed
setup to run with.

This adds a check for the common 'CI' environment variable that is
usually defined by all usual CI/CD pipelines to indicate a job is
running on a CI server to skip the detection regardless of preferences
configuration. If one absolutely want the feature even for CI, the
system-property 'DetectVMInstallationsJob.disabled' can be set to false
to restore previous behavior.

org.eclipse.jdt.launching/launching/org/eclipse/jdt/internal/launching/DetectVMInstallationsJob.java

@@ -46,6 +46,11 @@
  */
 public class DetectVMInstallationsJob extends Job {
 
+	/**
+	 * CI is a common variable defined in CI/CDI servers like Jenkins, Gitlab, Github, ... to indicate it is a CI environment
+	 */
+	private static final String ENV_CI = "CI"; //$NON-NLS-1$
+	private static final String PROPERTY_DETECT_VM_INSTALLATIONS_JOB_DISABLED = "DetectVMInstallationsJob.disabled"; //$NON-NLS-1$
 	private static final Object FAMILY = DetectVMInstallationsJob.class;
 
 	public DetectVMInstallationsJob() {
@@ -129,14 +134,7 @@ private boolean isDuplicateName(String name) {
 
 	private Collection<File> computeCandidateVMs(StandardVMType standardType) {
 		// parent directories containing a collection of VM installations
-		Collection<File> rootDirectories = new HashSet<>();
-		if (Platform.OS_WIN32.equals(Platform.getOS())) {
-			computeWindowsCandidates(rootDirectories);
-		} else {
-			rootDirectories.add(new File("/usr/lib/jvm")); //$NON-NLS-1$
-		}
-		rootDirectories.add(new File(System.getProperty("user.home"), ".sdkman/candidates/java")); //$NON-NLS-1$ //$NON-NLS-2$
-		rootDirectories.add(new File(miseDataDir(), "installs/java")); //$NON-NLS-1$
+		Collection<File> rootDirectories = List.of(new File("/opt/java")); //$NON-NLS-1$
 
 		Set<File> directories = rootDirectories.stream().filter(File::isDirectory)
 			.map(dir -> dir.listFiles(File::isDirectory))
@@ -168,38 +166,6 @@ private Collection<File> computeCandidateVMs(StandardVMType standardType) {
 			.collect(Collectors.toCollection(HashSet::new));
 	}
 
-	private void computeWindowsCandidates(Collection<File> rootDirectories) {
-		List<String> progFiles = List.of("ProgramFiles", "ProgramFiles(x86)"); //$NON-NLS-1$//$NON-NLS-2$
-		List<String> subDirs = List.of("Eclipse Adoptium", "RedHat");  //$NON-NLS-1$//$NON-NLS-2$
-		rootDirectories.addAll(
-		progFiles.stream()
-			.map(name -> System.getenv(name))
-			.filter(Objects::nonNull)
-			.distinct()
-			.flatMap(progFilesDir -> subDirs.stream().map(subDir -> new File(progFilesDir, subDir)))
-			.collect(Collectors.toList()));
-	}
-
-	private static File miseDataDir() {
-		String miseDataDir = System.getenv("MISE_DATA_DIR"); //$NON-NLS-1$
-		return miseDataDir != null ? new File(miseDataDir) : new File(xdgDataHome(), "mise"); //$NON-NLS-1$
-	}
-
-	private static File xdgDataHome() {
-		String xdgDataHome = System.getenv("XDG_DATA_HOME"); //$NON-NLS-1$
-		if (Platform.OS_WIN32.equals(Platform.getOS())) {
-			if (xdgDataHome == null) {
-				xdgDataHome = System.getenv("LOCALAPPDATA"); //$NON-NLS-1$
-			}
-			if (xdgDataHome == null) {
-				return new File(System.getProperty("user.home"), "AppData/Local"); //$NON-NLS-1$ //$NON-NLS-2$
-			}
-		} else if (xdgDataHome == null) {
-			return new File(System.getProperty("user.home"), ".local/share"); //$NON-NLS-1$ //$NON-NLS-2$
-		}
-		return new File(xdgDataHome);
-	}
-
 	private static Set<File> knownVMs() {
 		return Stream.of(JavaRuntime.getVMInstallTypes())
 			.map(IVMInstallType::getVMInstalls)
@@ -222,11 +188,20 @@ public boolean belongsTo(Object family) {
 	}
 
 	public static void initialize() {
-		boolean forcedDisableVMDetection = Boolean.getBoolean("DetectVMInstallationsJob.disabled"); //$NON-NLS-1$
+		boolean forcedDisableVMDetection = Boolean.getBoolean(PROPERTY_DETECT_VM_INSTALLATIONS_JOB_DISABLED);
+		if (forcedDisableVMDetection) {
+			// early exit no need to read preferences!
+			return;
+		}
+		if (System.getProperty(PROPERTY_DETECT_VM_INSTALLATIONS_JOB_DISABLED) == null && Boolean.parseBoolean(System.getenv(ENV_CI))) {
+			// exit because no explicit value for the property was given and we are running in a CI environment
+			return;
+		}
+		// finally look what is defined in the preferences
 		IEclipsePreferences instanceNode = InstanceScope.INSTANCE.getNode(LaunchingPlugin.getDefault().getBundle().getSymbolicName());
 		IEclipsePreferences defaultNode = DefaultScope.INSTANCE.getNode(LaunchingPlugin.getDefault().getBundle().getSymbolicName());
 		boolean defaultValue = defaultNode.getBoolean(LaunchingPlugin.PREF_DETECT_VMS_AT_STARTUP, true);
-		if (!forcedDisableVMDetection && instanceNode.getBoolean(LaunchingPlugin.PREF_DETECT_VMS_AT_STARTUP, defaultValue)) {
+		if (instanceNode.getBoolean(LaunchingPlugin.PREF_DETECT_VMS_AT_STARTUP, defaultValue)) {
 			new DetectVMInstallationsJob().schedule();
 		}
 	}