Crash with mapper transformer, OK without

[RobertBlackhart]

I am writing the client side of my application. In it I am requesting from the server a list of Auctions which are being encoded like this:

@app.Route('/list', methods: const[app.POST])
@Encode()
Future<List<Auction>> getAuctions(@app.Body(app.JSON) Map parameters)
{
    String queryString = "select * from auctions";
    return postgreSql.query(queryString, Auction);
}

The Auction class looks like this (on both ends):

class Auction
{
    @Field()
    String item_name;

    @Field()
    int item_count;

    @Field()
    int total_cost;

    @Field()
    String username;

    @Field()
    DateTime start_time;

    @Field()
    DateTime end_time;
}

The client-side code looks like this:

import 'package:redstone_mapper/mapper.dart';
import 'package:redstone_mapper/mapper_factory.dart';
import 'dart:convert';
import 'dart:html';

void main()
{
    bootstrapMapper();

    HttpRequest.request('http://localhost:8181/ah/list',
            method: "POST", requestHeaders: {"content-type": "application/json"},
            sendData: JSON.encode({'username':{'operator':'=','value':'thad'}}))
        .then((HttpRequest req)
        {
                List<Auction> auctions = decode(JSON.decode(req.responseText),Auction);
                print(auctions);
        });
}

My pubspec.yaml file has the redstone_mapper transformer listed (as suggested):

name: ah_test
description: A sample web application
dependencies:
  browser: any
  redstone: any
  redstone_mapper: any
  intl: any
transformers:
- redstone_mapper

However, when running the client, it throws an exception:

Exception: Uncaught Error: MapperException:  Failed to decode: {item_name: Pick, item_count: 5, total_cost: 1000, username: thad, start_time: 2014-08-27T19:15:00.000, end_time: 2014-08-29T19:15:00.000} 
reason: Class 'String' has no instance method 'toIso8601String'.

NoSuchMethodError: method not found: 'toIso8601String'
Receiver: "2014-08-27T19:15:00.000"
Arguments: []
Stack Trace:
#0      _getOrCreateMapper.<anonymous closure> (package:redstone_mapper/mapper_factory_static.dart:220:13)
#1      _ListDecoder.call.<anonymous closure> (package:redstone_mapper/mapper_factory_static.dart:167:21)
#2      MappedListIterable.elementAt (dart:_internal/iterable.dart:397)
#3      ListIterator.moveNext (dart:_internal/iterable.dart:325)
#4      List.List.from (dart:core/list.dart:95)
#5      _ListDecoder.call (package:redstone_mapper/mapper_factory_static.dart:166:16)
#6      _getOrCreateMapper.<anonymous closure> (package:redstone_mapper/mapper_factory_static.dart:213:52)
#7      _TypeDecoder.convert (package:redstone_mapper/src/mapper_impl.dart:32:26)
#8      GenericTypeCodec.decode (package:redstone_mapper/mapper.dart:282:28)
#9      decode (package:redstone_mapper/mapper.dart:30:29)
#10     main.<anonymous closure> (http://localhost:8080/ah_test.dart:40:38)
#11     _RootZone.runUnary (dart:async/zone.dart:1082)
#12     _Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:488)
#13     _Future._propagateToListeners (dart:async/future_impl.dart:571)
#14     _Future._completeWithValue (dart:async/future_impl.dart:331)
#15     _Future._asyncComplete.<anonymous closure> (dart:async/future_impl.dart:393)
#16     _asyncRunCallbackLoop (dart:async/schedule_microtask.dart:41)
#17     _asyncRunCallback (dart:async/schedule_microtask.dart:48)
#18     _handleMutation (dart:html:39006)

It looks like it's trying to parse the right thing, but it's failing to do the DateTime's correctly. The odd thing to me is that if I remove the redstone_mapper transformer, it runs without error and produces a correct result (I can manipulate the DateTime objects that are returned). Unfortunately, when compiling via pub build it does not run either way (with or without the transformer).

Am I doing something wrong with my code or is there a problem where the transformer is stripping out some class that is needed to decode the DateTime objects?

[luizmineo]

It seems the static implementation of mapper is not decoding DateTime objects correctly. I'll take a look at that.

When you run your code in Dartium, without running the transformer, it uses a different (dynamic) implementation, which seems to not be affected by this problem. Although, this implementation relies on the mirrors API, which can cause problems when compiled to Javascript.

[luizmineo]

I've just published redstone_mapper v0.1.6 with a fix for this problem. Can you try it again?

[RobertBlackhart]

I've just been able to try it again. I did a pub upgrade on both the server and the client and pulled in the new mapper package (0.1.6). Re-ran the code with the same results (same error message and stack trace). The problem still appears when using the transformer and disappears when removing the transformer.

[RobertBlackhart]

I take that last comment back. For whatever reason it is now working as expected (while having the transformer active). I can't really explain why it didn't work before other than something must have been cached.

I can also confirm that it works correctly when compiled to JS (and does not produce a bloated JS file).

[luizmineo]

Thanks! I'm trying to figure out how to automate tests for the static implementation (currently, only the dynamic implementation is covered by unit tests) so we can avoid errors like this.