[Haskell-cafe] api-tools questions

[Karsten Gebbert]

Hi Adam,

somehow I can't get it to work according to yours and Chris' examples. I
have the following test-case:

  -----

  stamp :: TimeStamp
    = basic string 
      with inj_TimeStamp, prj_TimeStamp
  
  test :: TestRec
    = record 
      created_at :: TimeStamp

  -----

  $(generate tests)
  
  -- created_at parses with:
  -- parseTime defaultTimeLocale "%Y-%m-%d %H:%M:%S%Q" a
  
  type TimeStamp = Maybe UTCTime

  inj_TimeStamp :: REP__TimeStamp -> ParserWithErrs TimeStamp
  inj_TimeStamp  (REP__TimeStamp as) = 
    return $ parseTime defaultTimeLocale "%Y-%m-%d %H:%M:%S%Q" (Text.unpack as)
  
  prj_TimeStamp :: TimeStamp -> REP__TimeStamp
  prj_TimeStamp (Just mp) = REP__TimeStamp $ 
    Text.pack $ formatTime defaultTimeLocale "%Y-%m-%d %H:%M:%S%Q" mp
  prj_TimeStamp  Nothing   = REP__TimeStamp $ 
    Text.pack ""
  
  $(generateAPITools tests [enumTool, jsonTool])


But, when I use it like this, I still get the format error:

   λ import qualified   Data.ByteString.Lazy as LBS                                       
   λ import Mytest.Types                                                        
   λ let a =  "{ \"created_at\": \"2014-09-10 14:06:48.13972\" }" :: LBS.ByteString       
   λ decodeWithErrs a :: Either [(JSONError, Position)] TestRec                           
   Left [(BadFormat FmtUTC "UTC" "2014-09-10 14:06:48.13972",[InField "created_at"])]      

It seems its not using the functions provided to parse the result at
all, if I put in some bogus stuff the conversion functions and set the
type of TimeStamp to Text, the created_at string appears in the output:

  inj_TimeStamp :: REP__TimeStamp -> ParserWithErrs TimeStamp
  inj_TimeStamp  (REP__TimeStamp _) = 
    return $ Text.pack "heheheheh"
  
  prj_TimeStamp :: TimeStamp -> REP__TimeStamp
  prj_TimeStamp _ = REP__TimeStamp $ Text.pack "Hohoho"

  λ let a =  "{ \"created_at\": \"2014-09-10 14:06:48.13972\" }" :: LBS.ByteString        
  λ decodeWithErrs a :: Either [(JSONError, Position)] TextRec                            
  Right (TextRec {_test_created_at = "2014-09-10 14:06:48.13972"})                         

I'm probably missing something really simple here, but maybe you can
spot it quicker than I do.. I'll investigate more when I'm back home
anyways.

Thanks for any hints!

k

Adam Gundry <adam at well-typed.com> writes:

> Hi Karsten,
>
> This isn't very well documented, but there is a (hidden) feature of
> api-tools that should do what you want. If you say something like
>
>     mt :: MyTime = basic string with inj_MyTime, prj_MyTime
>
> then you can define your own type MyTime and give conversion functions
> inj_MyTime and prj_MyTime to convert back and forth from a
> newtype-wrapped Text. (In fact, you could probably use UTCTime as
> MyTime...). More precisely, api-tools will generate something like
>
>     newtype REP__MyTime = REP__MyTime Text
>
> and you will need to implement
>
>     inj_MyTime :: REP__MyTime -> ParserWithErrs MyTime
>     prj_MyTime :: MyTime -> REP__MyTime
>
> I hope this helps, and further questions or documentation contributions
> are very welcome!
>
> Cheers,
>
> Adam
>
>
> On 09/09/14 14:02, Karsten Gebbert wrote:
>> Hi All,
>> 
>> I have a question concerning the api-tools package.
>> 
>> Its not clear from the tests, sources or the tutorial how I can use
>> other date/time formats that the default `utc` type can handle. I'm
>> trying to wrap a JSON API that is not under my control, so I have to
>> adhere to whatever I get back from it. Could anybody with experience
>> with the package point me to some example, relevant bits in the sources
>> or a tip how to do it?
>> 
>> I'm planning to create some more documentation around the package to
>> contribute back once I figured out a few more details, because I think
>> its quite a useful abstraction when dealing with (foreign) APIs IMO.
>> 
>> Thanks already for any hints,
>> 
>> karsten
>
>
> -- 
> Adam Gundry, Haskell Consultant
> Well-Typed LLP, http://www.well-typed.com/