[2029] Fallback to default charset if the charset provided by sun.st*…

….encoding is invalid

src/main/java/picocli/CommandLine.java

@@ -15045,7 +15045,15 @@ static Charset getStderrEncoding() {
     static Charset charsetForName(String encoding) {
         if (encoding != null) {
             if ("cp65001".equalsIgnoreCase(encoding)) { encoding = "UTF-8"; } // #1474 MS Windows uses code page 65001 for UTF8
-            return Charset.forName(encoding);
+            try {
+                return Charset.forName(encoding);
+            } catch (Exception e) {
+                // fallback to default charset if the requested encoding is not available
+                final Charset defaultCharset = Charset.defaultCharset();
+                CommandLine.tracer().info("The %s encoding in not available, falling back to %s", encoding,
+                    defaultCharset.name());
+                return defaultCharset;
+            }
         }
         return Charset.defaultCharset();
     }
@@ -18705,7 +18713,7 @@ private List<String> prefixCommandName(List<String> suggestions)
             if(commandName == null || commandName.trim().isEmpty()) { return suggestions; }
             List<String> prefixedSuggestions = new ArrayList<String>();
             for (String s : suggestions) {
-                prefixedSuggestions.add(commandName + " " + s);    
+                prefixedSuggestions.add(commandName + " " + s);
             }
             return prefixedSuggestions;
         }

src/test/java/picocli/Issue2029.java

@@ -0,0 +1,55 @@
+package picocli;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.contrib.java.lang.system.RestoreSystemProperties;
+import org.junit.contrib.java.lang.system.SystemErrRule;
+import org.junit.contrib.java.lang.system.SystemOutRule;
+import org.junit.rules.TestRule;
+
+import static org.junit.Assert.assertEquals;
+
+public class Issue2029 {
+    @Rule
+    public final TestRule restoreSystemProperties = new RestoreSystemProperties();
+
+    @Rule
+    public final SystemOutRule systemOutRule = new SystemOutRule().enableLog();
+
+    @Rule
+    public final SystemErrRule systemErrRule = new SystemErrRule().enableLog();
+
+    @CommandLine.Command(name = "test")
+    static class TestCommand implements Runnable {
+
+        @CommandLine.Parameters
+        String text;
+
+        @CommandLine.Spec
+        CommandLine.Model.CommandSpec spec;
+
+        //@Override
+        public void run() {
+            spec.commandLine().getOut().print(text);
+            spec.commandLine().getOut().flush();
+            spec.commandLine().getErr().print(text);
+            spec.commandLine().getErr().flush();
+        }
+    }
+
+    @Test
+    public void invalidEncodingFallsbackToDefaultEncoding() {
+        resetLogs();
+        System.setProperty("sun.stdout.encoding", "cp0");
+        System.setProperty("sun.stdout.encoding", "cp0");
+
+        assertEquals(CommandLine.ExitCode.OK, new CommandLine(new Issue1320.TestCommand()).execute("test"));
+        assertEquals("test", systemOutRule.getLog());
+        assertEquals("test", systemErrRule.getLog());
+    }
+
+    private void resetLogs() {
+        systemOutRule.clearLog();
+        systemErrRule.clearLog();
+    }
+}