map := [:] { ordered = true }
map["key0"] = "value0"
map["key1"] = "value1"

buf := Buf().writeObj(map).flip

deserializedMap := buf.readObj as Map
echo(deserializedMap.ordered)

prints

false

That is by design since ordered state isn't serializable. One option would be to always use ordered (treemap) implementation in the decoder. It would be a bit slower, but might give more robust results which always match the text deserialized. I'd like to hear some feedback and support for that change before making it though

Why not add it as a deserialization option?

The test case just looks like a bug to me. "ordered" is a key part of the state and should be serialised.

I agree with jodastephen :)

I've just been bit by this.

I was storing some data in a WebSession and was expecting my data to be regurgitated in the same state as it went in. As it stands my map data comes back in a different order than it went in.

You wouldn't expect the values of a list to come back all jumbled up! The same goes for an ordered map.

Could ordered and caseInsensitive be serialised with the map, and be read back first before the data?

Promoted to ticket #2059 and assigned to brian

I think what I finally decided in JSON was to always deserialize maps in order. Its a bit slower, but simplest solution for "just works"

Ticket resolved in 1.0.67

Change fantom deserialization to always use ordered maps to match the behavior in JSON. This doesn't actually maintain the ordered/case insensitive state - that would require redesigning the serialize syntax itself.

Cool, I saw the LinkedHashMap change!

This doesn't actually maintain the ordered/case insensitive state

Fair enough, could a sentence to this effect be added to the docs, so it doesn't catch people out?

I noted that the Fantom JS implementation doesn't have this change, which can (or did!) trip you up when passing data from a (Java) server to a (JS) browser.

I think this (untested) patch may be all that's needed:

diff -r b0eaa6515889 src/sys/js/fanx/ObjDecoder.js
--- a/src/sys/js/fanx/ObjDecoder.js	Thu Jan 11 09:57:00 2018 -0500
+++ b/src/sys/js/fanx/ObjDecoder.js	Fri Jan 12 14:11:19 2018 +0000
@@ -445,6 +445,7 @@
   var map = mapType == null
     ? fan.sys.Map.make(fan.sys.Obj.$type, fan.sys.Obj.$type.toNullable())
     : fan.sys.Map.make(mapType);
+  map.m_ordered = true;
 
   // finish first pair
   this.consume(fanx_Token.COLON, "Expected ':'");

Is there a test in test suite somewhere we can check against?

I found this in /testSys/fan/TestSerialization.fan:

// test ordering
Str:Int m := verifySer("""["b":1, "a":2, "c":5, "e":3, "f":3]""",  ["b":1, "a":2, "c":5, "e":3, "f":3])
verifyEq(m.keys, ["b", "a", "c", "e", "f"])

If it happens to pass, my issue used Uri as the key.

Thanks Steve -- I'm going to split this out into a sep ticket