Don't deserialize Arrays into lists for empty data decls

Author: bergmark

js/runtime.js

@@ -394,18 +394,18 @@ function Fay$$jsToFay(type,jsObj){
       type.push(["automatic"]);
     return Fay$$jsToFay(["function", type], jsObj);
   }
+  else if(base == "automatic" && jsObj instanceof Array) {
+    var list = null;
+    for (var i = jsObj.length - 1; i >= 0; i--) {
+      list = new Fay$$Cons(Fay$$jsToFay([base], jsObj[i]), list);
+    }
+    return list;
+  }
   else if(base == "automatic" || base == "user") {
     if (jsObj && jsObj['instance']) {
       var jsToFayFun = Fay$$jsToFayHash[jsObj["instance"]];
       return jsToFayFun ? jsToFayFun(type,type[2],jsObj) : jsObj;
     }
-    else if (jsObj instanceof Array) {
-      var list = null;
-      for (var i = jsObj.length - 1; i >= 0; i--) {
-        list = new Fay$$Cons(Fay$$jsToFay([base], jsObj[i]), list);
-      }
-      return list;
-    }
     else
       return jsObj;
   }

tests/EmptyDataDeclArray.hs

@@ -0,0 +1,20 @@
+import FFI
+
+data Array a
+
+empty :: Fay (Array a)
+empty = ffi "[]"
+
+push:: a -> Array a -> Fay ()
+push = ffi "%2.push(%1)"
+
+len :: Array a -> Fay Int
+len = ffi "%1['length']"
+
+main :: Fay ()
+main = do
+  arr <- empty
+  print arr
+  push (5::Int) arr
+  print =<< len arr
+  print arr

tests/EmptyDataDeclArray.res

@@ -0,0 +1,3 @@
+[]
+1
+[ 5 ]