[remkop#1706] Resolve messages against parent resource bundles

src/main/java/picocli/CommandLine.java

@@ -40,6 +40,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+
 import picocli.CommandLine.Help.Ansi.IStyle;
 import picocli.CommandLine.Help.Ansi.Style;
 import picocli.CommandLine.Help.Ansi.Text;
@@ -11558,6 +11559,7 @@ public static class Messages {
             private final String bundleBaseName;
             private final ResourceBundle rb;
             private final Set<String> keys;
+            private Messages parent;
             public Messages(CommandSpec spec, String baseName) {
                 this(spec, baseName, createBundle(baseName));
             }
@@ -11581,6 +11583,21 @@ private static String extractName(ResourceBundle rb) {
                     return (String) ResourceBundle.class.getDeclaredMethod("getBaseBundleName").invoke(rb);
                 } catch (Exception ignored) { return "?"; }
             }
+            public Messages parent() {
+            	CommandSpec parentSpec = this.spec.parent();
+            	if ( parent==null || parent.spec!=parentSpec ) {
+            		parent = null; // Refresh if parentSpec doesn't match
+            		while ( parent==null && parentSpec!=null ) {
+		            	String parentResourceBundleBaseName = parentSpec.resourceBundleBaseName();
+		            	if ( parentResourceBundleBaseName!=null && !parentResourceBundleBaseName.equals(this.bundleBaseName)) {
+		            		parent = new Messages(parentSpec, parentResourceBundleBaseName);
+		            	} else {
+		            		parentSpec = parentSpec.parent();
+		            	}
+            		}
+            	}
+	            return parent;
+            }
             private static Set<String> keys(ResourceBundle rb) {
                 if (rb == null) { return Collections.emptySet(); }
                 Set<String> keys = new LinkedHashSet<String>();
@@ -11596,8 +11613,8 @@ private static Set<String> keys(ResourceBundle rb) {
             public static Messages copy(CommandSpec spec, Messages original) {
                 return original == null ? null : new Messages(spec, original.bundleBaseName, original.rb);
             }
-            /** Returns {@code true} if the specified {@code Messages} is {@code null} or has a {@code null ResourceBundle}. */
-            public static boolean empty(Messages messages) { return messages == null || messages.rb == null; }
+            /** Returns {@code true} if the specified {@code Messages} is {@code null}, has a {@code null ResourceBundle}, or has a {@code null parent Messages}. */
+            public static boolean empty(Messages messages) { return messages == null || messages.isEmpty(); }
 
             /** Returns the String value found in the resource bundle for the specified key, or the specified default value if not found.
              * @param key unqualified resource bundle key. This method will first try to find a value by qualifying the key with the command's fully qualified name,
@@ -11608,12 +11625,19 @@ public static Messages copy(CommandSpec spec, Messages original) {
             public String getString(String key, String defaultValue) {
                 if (isEmpty()) { return defaultValue; }
                 String cmd = spec.qualifiedName(".");
-                if (keys.contains(cmd + "." + key)) { return rb.getString(cmd + "." + key); }
-                if (keys.contains(key)) { return rb.getString(key); }
-                return defaultValue;
+                String qualifiedKey = cmd + "." + key;
+                String result = getStringForExactKey(qualifiedKey);
+                if ( result==null ) { result = getStringForExactKey(key); }
+                return result!=null ? result : defaultValue;
+            }
+
+            private String getStringForExactKey(String key) {
+            	if (keys.contains(key)) { return rb.getString(key); }
+            	else if (parent()!=null) { return parent().getStringForExactKey(key); }
+            	else { return null; }
             }
 
-            boolean isEmpty() { return rb == null || keys.isEmpty(); }
+            boolean isEmpty() { return (rb == null || keys.isEmpty()) && (parent()==null || parent().isEmpty()); }
 
             /** Returns the String array value found in the resource bundle for the specified key, or the specified default value if not found.
              * Multi-line strings can be specified in the resource bundle with {@code key.0}, {@code key.1}, {@code key.2}, etc.
@@ -11625,10 +11649,15 @@ public String getString(String key, String defaultValue) {
             public String[] getStringArray(String key, String[] defaultValues) {
                 if (isEmpty()) { return defaultValues; }
                 String cmd = spec.qualifiedName(".");
-                List<String> result = addAllWithPrefix(rb, cmd + "." + key, keys, new ArrayList<String>());
-                if (!result.isEmpty()) { return result.toArray(new String[0]); }
-                addAllWithPrefix(rb, key, keys, result);
-                return result.isEmpty() ? defaultValues : result.toArray(new String[0]);
+                String qualifiedKey = cmd + "." + key;
+                String[] result = getStringArrayForExactKey(qualifiedKey);
+                if ( result==null ) { result = getStringArrayForExactKey(key); }
+                return result!=null ? result : defaultValues;
+            }
+            private String[] getStringArrayForExactKey(String key) {
+            	List<String> result = addAllWithPrefix(rb, key, keys, new ArrayList<String>());
+            	if (!result.isEmpty()) { return result.toArray(new String[0]); }
+            	return parent()==null ? null : parent().getStringArrayForExactKey(key);
             }
             private static List<String> addAllWithPrefix(ResourceBundle rb, String key, Set<String> keys, List<String> result) {
                 if (keys.contains(key)) { result.add(rb.getString(key)); }