Warn if the user sets a property that we don't recognise.

Author: chrisseaton

core/src/main/java/org/jruby/util/cli/ArgumentProcessor.java

@@ -39,9 +39,7 @@
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
+import java.util.*;
 
 /**
  * Encapsulated logic for processing JRuby's command-line arguments.
@@ -94,6 +92,8 @@ public void processArguments() {
     }
 
     public void processArguments(boolean inline) {
+        checkProperties();
+
         while (argumentIndex < arguments.size() && isInterpreterArgument(arguments.get(argumentIndex).originalValue)) {
             processArgument();
             argumentIndex++;
@@ -679,4 +679,24 @@ public static void checkGraalVersion() {
         }
     }
 
+    private void checkProperties() {
+        final Set<String> propertyNames = new HashSet<>();
+        propertyNames.addAll(Options.getPropertyNames());
+        propertyNames.add("jruby.home");
+        propertyNames.add("jruby.script");
+        propertyNames.add("jruby.shell");
+        propertyNames.add("jruby.lib");
+        propertyNames.add("jruby.bindir");
+        propertyNames.add("jruby.jar");
+        propertyNames.add("jruby.compat.version");
+
+        for (String propertyName : System.getProperties().stringPropertyNames()) {
+            if (propertyName.startsWith("jruby.")) {
+                if (!propertyNames.contains(propertyName)) {
+                    System.err.println("jruby: warning: unknown property " + propertyName);
+                }
+            }
+        }
+    }
+
 }

core/src/main/java/org/jruby/util/cli/Options.java

@@ -28,10 +28,7 @@
  ***** END LICENSE BLOCK *****/
 package org.jruby.util.cli;
 
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
+import java.util.*;
 
 import com.headius.options.Option;
 import org.jruby.TruffleBridge;
@@ -338,4 +335,14 @@ private static void list(SearchMode mode, String string) {
         }
     }
 
+    public static Set<String> getPropertyNames() {
+        final Set<String> propertyNames = new HashSet<String>();
+
+        for (Option option : PROPERTIES) {
+            propertyNames.add(option.propertyName());
+        }
+
+        return Collections.unmodifiableSet(propertyNames);
+    }
+
 }