could not parse: `' (input does not start with a digit)

[picca]

Hello,
I try to use a webform with a Maybe Float

but I get this error message when it tries to parse the parameter resolution.

here the request from servant

Oct 15 11:33:38 process2 autoprocessing-exe[171261]: POST /xdsme
Oct 15 11:33:38 process2 autoprocessing-exe[171261]:   Params: [("dataCollectionId","0"),("resolution",""),("optimize","0"),("celll",""),("spacegroup","")]
Oct 15 11:33:38 process2 autoprocessing-exe[171261]:   Request Body: dataCollectionId=0&resolution=&optimize=0&celll=&spacegroup=
Oct 15 11:33:38 process2 autoprocessing-exe[171261]:   Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Oct 15 11:33:38 process2 autoprocessing-exe[171261]:   Status: 400 Bad Request 0.0003s

could not parse: `' (input does not start with a digit)

Indeed "" is not a float, but in that case I expect Nothing.

So where is the problem ?

[phadej]

Won't fix.

In servant:

• the Maybe indicate the absence of QueryParam.
• you should
  • either use a newtype to special case "" case (which isn't valid Int)
  • use QueryParam' '[Optional, Lenient] so you'll get Maybe (Either Text a) and then you can do parsing choices in the hander.