Bug 573712: Populate WSL entries in terminal list like git bash is

Change-Id: I371d5455296e9d1bcb9137e538d5cc2ed5417ba1

terminal/plugins/org.eclipse.tm.terminal.view.ui/src/org/eclipse/tm/terminal/view/ui/local/showin/ExternalExecutablesManager.java

@@ -31,6 +31,7 @@ import org.eclipse.core.runtime.Platform;
 import org.eclipse.tm.terminal.view.ui.activator.UIPlugin;
 import org.eclipse.tm.terminal.view.ui.internal.ExternalExecutablesState;
 import org.eclipse.tm.terminal.view.ui.local.showin.detectors.DetectGitBash;
+import org.eclipse.tm.terminal.view.ui.local.showin.detectors.DetectWSL;
 import org.eclipse.ui.PlatformUI;
 import org.eclipse.ui.services.ISourceProviderService;
 
@@ -39,7 +40,7 @@ import org.eclipse.ui.services.ISourceProviderService;
  */
 public class ExternalExecutablesManager {
 	// XXX: This may make a useful extension point?
-	private static List<IDetectExternalExecutable> detectors = List.of(new DetectGitBash());
+	private static List<IDetectExternalExecutable> detectors = List.of(new DetectGitBash(), new DetectWSL());
 
 	public static boolean hasEntries() {
 		IPath stateLocation = UIPlugin.getDefault().getStateLocation();

terminal/plugins/org.eclipse.tm.terminal.view.ui/src/org/eclipse/tm/terminal/view/ui/local/showin/detectors/DetectWSL.java

@@ -0,0 +1,111 @@
+/*******************************************************************************
+ * Copyright (c) 2021 Kichwa Coders Canada Inc. and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package org.eclipse.tm.terminal.view.ui.local.showin.detectors;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Predicate;
+
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.tm.terminal.view.ui.interfaces.IExternalExecutablesProperties;
+import org.eclipse.tm.terminal.view.ui.local.showin.IDetectExternalExecutable;
+
+public class DetectWSL implements IDetectExternalExecutable {
+
+	/**
+	 * Don't access directly, use {@link #getEntries()}
+	 */
+	List<Map<String, String>> result = null;
+
+	@Override
+	public boolean hasEntries() {
+		return !getEntries().isEmpty();
+	}
+
+	@Override
+	public List<Map<String, String>> getEntries(List<Map<String, String>> externalExecutables) {
+		List<Map<String, String>> newEntries = new ArrayList<>();
+		var entries = getEntries();
+		for (var map : entries) {
+			String name = map.get(IExternalExecutablesProperties.PROP_NAME);
+			if (externalExecutables.stream().map(m -> m.get(IExternalExecutablesProperties.PROP_NAME))
+					.noneMatch(Predicate.isEqual(name))) {
+				newEntries.add(map);
+			}
+		}
+		return newEntries;
+	}
+
+	private synchronized List<Map<String, String>> getEntries() {
+		if (result == null) {
+			result = Collections.emptyList();
+			if (Platform.OS_WIN32.equals(Platform.getOS())) {
+				String windir = System.getenv("windir"); //$NON-NLS-1$
+				if (windir == null) {
+					return result;
+				}
+				String wsl = windir + "\\System32\\wsl.exe"; //$NON-NLS-1$
+				if (!Files.isExecutable(Paths.get(wsl))) {
+					return result;
+				}
+
+				ProcessBuilder pb = new ProcessBuilder(wsl, "--list", "--quiet"); //$NON-NLS-1$ //$NON-NLS-2$
+				try {
+					Process process = pb.start();
+					try (InputStream is = process.getErrorStream()) {
+						// drain the error stream
+						if (is.readAllBytes().length != 0) {
+							return result;
+						}
+					}
+
+					try (BufferedReader reader = new BufferedReader(
+							new InputStreamReader(process.getInputStream(), StandardCharsets.UTF_16LE))) {
+						result = new ArrayList<>();
+						String line = null;
+						while ((line = reader.readLine()) != null) {
+							String distribution = line.trim();
+							if (distribution.isBlank()) {
+								continue;
+							}
+							// docker-desktop entries are not "real" so shouldn't be shown in UI
+							if (distribution.startsWith("docker-desktop")) { //$NON-NLS-1$
+								continue;
+							}
+
+							String name = distribution + " (WSL)"; //$NON-NLS-1$
+							Map<String, String> m = new HashMap<>();
+							m.put(IExternalExecutablesProperties.PROP_NAME, name);
+							m.put(IExternalExecutablesProperties.PROP_PATH, wsl);
+							m.put(IExternalExecutablesProperties.PROP_ARGS, "--distribution " + distribution); //$NON-NLS-1$
+							m.put(IExternalExecutablesProperties.PROP_TRANSLATE, Boolean.TRUE.toString());
+							result.add(m);
+						}
+					}
+
+				} catch (IOException e) {
+				}
+			}
+		}
+		return result;
+	}
+
+}