Fix decoding of JavaScriptCodeWithScope

Read the first i32 off the code_w_s

Author: alanhdu

src/decoder/mod.rs

@@ -152,6 +152,10 @@ fn decode_bson<R: Read + ?Sized>(reader: &mut R, tag: u8) -> DecoderResult<Bson>
         },
         Some(JavaScriptCode) => read_string(reader).map(Bson::JavaScriptCode),
         Some(JavaScriptCodeWithScope) => {
+            // disregard the length:
+            //     using Read::take causes infinite type recursion
+            try!(read_i32(reader));
+
             let code = try!(read_string(reader));
             let scope = try!(decode_document(reader));
             Ok(Bson::JavaScriptCodeWithScope(code, scope))

tests/modules/encoder_decoder.rs

@@ -148,8 +148,8 @@ fn test_encode_decode_javascript_code_with_scope() {
 
     assert_eq!(buf, dst);
 
-    //let decoded = decode_document(&mut Cursor::new(buf)).unwrap();
-    //assert_eq!(decoded, doc);
+    let decoded = decode_document(&mut Cursor::new(buf)).unwrap();
+    assert_eq!(decoded, doc);
 }
 
 #[test]