Fix for jruby/jruby#8178 by only allowing a RubyArray into Argv

fix_8718_attempt_1.diff

diff --git a/core/src/main/java/org/jruby/embed/variable/AbstractVariable.java b/core/src/main/java/org/jruby/embed/variable/AbstractVariable.java
index 46177487d7..85ede943b4 100644
--- a/core/src/main/java/org/jruby/embed/variable/AbstractVariable.java
+++ b/core/src/main/java/org/jruby/embed/variable/AbstractVariable.java
@@ -104,8 +104,15 @@ abstract class AbstractVariable implements BiVariable {
         } else {
             javaType = javaObject.getClass();
         }
+
+        updateRubyObjectFromJavaObject(runtime);
+    }
+
+    protected IRubyObject updateRubyObjectFromJavaObject(final Ruby runtime) {
         rubyObject = JavaEmbedUtils.javaToRuby(runtime, javaObject);
         fromRuby = false;
+
+        return rubyObject;
     }
 
     protected void updateRubyObject(final IRubyObject rubyObject) {
diff --git a/core/src/main/java/org/jruby/embed/variable/Argv.java b/core/src/main/java/org/jruby/embed/variable/Argv.java
index ad8559f10c..d35c20769b 100644
--- a/core/src/main/java/org/jruby/embed/variable/Argv.java
+++ b/core/src/main/java/org/jruby/embed/variable/Argv.java
@@ -38,6 +38,7 @@ import org.jruby.RubyModule;
 import org.jruby.RubyNil;
 import org.jruby.RubyObject;
 import org.jruby.embed.internal.BiVariableMap;
+import org.jruby.javasupport.JavaEmbedUtils;
 import org.jruby.runtime.builtin.IRubyObject;
 
 /**
@@ -117,14 +118,7 @@ public class Argv extends AbstractVariable {
     public void inject() {
         final Ruby runtime = getRuntime();
 
-        final RubyArray argv = RubyArray.newArray(runtime);
-        if ( javaObject instanceof Collection ) {
-            argv.addAll( (Collection) javaObject );
-        }
-        else if ( javaObject instanceof String[] ) {
-            for ( String str : (String[]) javaObject ) argv.add(str);
-        }
-        this.rubyObject = argv; fromRuby = true;
+        IRubyObject argv = updateRubyObjectFromJavaObject(runtime);
 
         RubyModule rubyModule = getRubyClass(runtime);
         // SSS FIXME: With rubyclass stack gone, this needs a replacement
@@ -136,6 +130,20 @@ public class Argv extends AbstractVariable {
         runtime.getConstantInvalidator(name).invalidate();
     }
 
+    protected IRubyObject updateRubyObjectFromJavaObject(final Ruby runtime) {
+        final RubyArray argv = RubyArray.newArray(runtime);
+        if ( javaObject instanceof Collection) {
+            argv.addAll( (Collection) javaObject );
+        }
+        else if ( javaObject instanceof String[] ) {
+            for ( String str : (String[]) javaObject ) argv.add(str);
+        }
+        this.rubyObject = argv;
+        this.fromRuby = true;
+
+        return argv;
+    }
+
     /**
      * Removes this object from {@link BiVariableMap}. Also, initialize
      * this variable in top self.