[Truffle] Implement a couple things to make MSpec auto add tags work.

* Fix order of methods.
* File#exist? should just check existance, not file type.
* Will not work if the directory does not exist, but that sounds rather rare.

core/src/main/java/org/jruby/truffle/nodes/core/FileNodes.java

@@ -175,42 +175,42 @@ public RubyNilClass eachLine(VirtualFrame frame, RubyFile file, RubyProc block)
 
     }
 
-    @CoreMethod(names = {"exist?", "exists?"}, onSingleton = true, required = 1)
-    public abstract static class ExistsNode extends CoreMethodNode {
+    @CoreMethod(names = "executable?", onSingleton = true, required = 1)
+    public abstract static class ExecutableNode extends CoreMethodNode {
 
-        public ExistsNode(RubyContext context, SourceSection sourceSection) {
+        public ExecutableNode(RubyContext context, SourceSection sourceSection) {
             super(context, sourceSection);
         }
 
-        public ExistsNode(ExistsNode prev) {
+        public ExecutableNode(ExecutableNode prev) {
             super(prev);
         }
 
         @Specialization
-        public boolean exists(RubyString path) {
+        public boolean executable(RubyString path) {
             notDesignedForCompilation();
 
-            return new File(path.toString()).isFile();
+            return new File(path.toString()).canExecute();
         }
 
     }
 
-    @CoreMethod(names = "executable?", onSingleton = true, required = 1)
-    public abstract static class ExecutableNode extends CoreMethodNode {
+    @CoreMethod(names = {"exist?", "exists?"}, onSingleton = true, required = 1)
+    public abstract static class ExistsNode extends CoreMethodNode {
 
-        public ExecutableNode(RubyContext context, SourceSection sourceSection) {
+        public ExistsNode(RubyContext context, SourceSection sourceSection) {
             super(context, sourceSection);
         }
 
-        public ExecutableNode(ExecutableNode prev) {
+        public ExistsNode(ExistsNode prev) {
             super(prev);
         }
 
         @Specialization
-        public boolean executable(RubyString path) {
+        public boolean exists(RubyString path) {
             notDesignedForCompilation();
 
-            return new File(path.toString()).canExecute();
+            return new File(path.toString()).exists();
         }
 
     }
@@ -298,6 +298,26 @@ public static void join(StringBuilder builder, Object[] parts) {
         }
     }
 
+    @CoreMethod(names = "path", onSingleton = true, required = 1)
+    public abstract static class PathNode extends CoreMethodNode {
+
+        public PathNode(RubyContext context, SourceSection sourceSection) {
+            super(context, sourceSection);
+        }
+
+        public PathNode(PathNode prev) {
+            super(prev);
+        }
+
+        @Specialization
+        public RubyString path(RubyString path) {
+            notDesignedForCompilation();
+
+            return getContext().makeString(path.toString());
+        }
+
+    }
+
     @CoreMethod(names = "puts", required = 1)
     public abstract static class PutsNode extends CoreMethodNode {
 

core/src/main/java/org/jruby/truffle/runtime/core/RubyFile.java

@@ -98,6 +98,14 @@ public static RubyFile open(RubyContext context, String fileName, String mode) {
             } catch (FileNotFoundException e) {
                 throw new RuntimeException(e);
             }
+        } else if (mode.equals("a") || mode.equals("ab")) {
+            reader = null;
+
+            try {
+                writer = new OutputStreamWriter(new FileOutputStream(fileName, true));
+            } catch (FileNotFoundException e) {
+                throw new RuntimeException(e);
+            }
         } else {
             throw new UnsupportedOperationException();
         }