Re: [Haskell-cafe] Problem with monadic formlets
Hey everybody, I've just uploaded formlets 0.6.1 to Hackage, which should fix this bug. Thanks for letting me know! -chris On 29 aug 2009, at 13:22, Jeremy Shaw wrote: Hello, Yeah, it seems that checkM in formlets 0.6 broken. I reported the bug to MightByte as well. - jeremy At Fri, 28 Aug 2009 12:49:08 +0100, Colin Paul Adams wrote: Colin == Colin Paul Adams co...@colina.demon.co.uk writes: Jeremy == Jeremy Shaw jer...@n-heptane.com writes: Colin apparent data corruprion is occurring. I am suspecting a Colin bug in the formlets library (I have version 0.6). Colin So I have created a slightly cut-down (no database Colin involved) complete working program. Can you see if this Colin works ok with your version of formlets: I managed to uninstall formlets-0.6 myself, and then installed 0.5 instead. After adding the necessary extra argument to runFormletState (an empty string), the test program works fine. So this seems to be a bug in formlets-0.6. -- Colin Adams Preston Lancashire ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem with monadic formlets
Chris Hey everybody, I've just uploaded formlets 0.6.1 to Chris Hackage, which should fix this bug. Thanks for letting me Chris know! Yes, it does fix it. Thanks. -- Colin Adams Preston Lancashire ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem with monadic formlets
Hello, Yeah, it seems that checkM in formlets 0.6 broken. I reported the bug to MightByte as well. - jeremy At Fri, 28 Aug 2009 12:49:08 +0100, Colin Paul Adams wrote: Colin == Colin Paul Adams co...@colina.demon.co.uk writes: Jeremy == Jeremy Shaw jer...@n-heptane.com writes: Colin apparent data corruprion is occurring. I am suspecting a Colin bug in the formlets library (I have version 0.6). Colin So I have created a slightly cut-down (no database Colin involved) complete working program. Can you see if this Colin works ok with your version of formlets: I managed to uninstall formlets-0.6 myself, and then installed 0.5 instead. After adding the necessary extra argument to runFormletState (an empty string), the test program works fine. So this seems to be a bug in formlets-0.6. -- Colin Adams Preston Lancashire ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem with monadic formlets
At Sat, 29 Aug 2009 15:46:42 +0100,
Chris Eidhof (formlets) wrote:
Confirmed. checkM is broken, thanks for noticing! I'll have a look
into it, I'm not sure whether it can be fixed. I was thinking of
removing all the monadic stuff from the formlets. I think this will
make for a much cleaner interface, monadic checking can then be done
afterwards.
I am still a fan of (and use) this version of Form:
newtype Form xml m a = Form { deform :: Env - State FormState (Collector (m
(Failing a)), xml, FormContentType) }
not sure how I would feel about the removal of 'm' from the
Collector. But 'xml' is nicer for me than 'm xml' because my collector
and xml generator are often in different monads. I can, of course make
them be in the same monad if I want:
type MyForm a = Form (IO XML) IO a
but I also have the option of just doing:
type MyForm a = Form (IO XML) IO a
or:
type MyForm a = Form (HSP XML) IO a
At present, I actually have my collector do all the validation and
update the database. As a use case, let's assume that the form is
creating a new user account. One possible error would be using a
username that is already in use. Doing that check requires a database
query. In fact, it seems best if it does a database update, so that
there is no race condition between checking if the name is in use, and
actually attempting to create the account with that username.
If you remove the ability to do IO in the collector, then I believe I
would need to:
1. run the collector to do the pure part of the validation.
2. if the pure part succeeds, use the returned value to do the impure
validation
3. if that fails, then redisplay the form using the same environment
that I used for #1, but passing in the impure validation errors.
One potential drawback that I see with this is that it may make it
difficult to the pass the error messages back to the specific formlet
element that failed so that you can display the errors in-line.
[Note: the following discussion reflects the pre-0.6 design].
Currently the environment we pass in is something like:
type Env = [(String, Either String File)]
The first component of the tuple is the name of the element. aka,
input0, input1, etc.
I would propose that we also pass in a Failures argument:
type Failures = [(String, ErrorMsg)]
where the first component of the tuple is the name of the element
(input0, intpu1, etc) and the second element contains ErrorMsg.
or perhaps modify Env to:
type Env = [(String, (Maybe ErrorMsg, Either String File)]
We would need to modify the Failing data type to:
data Failing a = Failure [(String, ErrorMsg)] | Success a
so that Failures would contain their location.
Not all errors correspond to a specific form element. Let's say that
you have 3 drop-down boxes that combine together to form a date
selector. You want to validate the result of all three combined to
make sure they picked a valid date, and if it is invalid, you produce
an error message for that group, not a specific element. The problem
then is that there is no 'location' that corresponds to that group, so
what do you put in the Failure tuple?
I think you can use freshName to generate an extra 'virtual' name that
corresponds to the group as a whole.
I have been meaning to prototype this in the near future and see if it
actually works. I'll try to get something worked up in the next two
weeks (my sister is getting married next week, so my schedule is
pretty full).
- jeremy
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Re: [Haskell-cafe] Problem with monadic formlets
Jeremy == Jeremy Shaw jer...@n-heptane.com writes:
Jeremy Hello, I hacked your code into a runnable example, and it
Jeremy seems to work for me.
Jeremy Which looks correct to me. Your code looks fine to me as
Jeremy well... Perhaps the error is not in the code you pasted,
Jeremy but somewhere else. I am running on an older, and somewhat
Jeremy forked version of Formlets, so there could also be a bug
Jeremy in the new code I guess. Though, that seems unlikely. But
Jeremy it is worth noting that we are not using the same version
Jeremy of the formlets library.
I did some debugging in ghci, but was unable to step through the
ensure and check routines, which is where the apparent data corruprion
is occurring. I am suspecting a bug in the formlets library (I have
version 0.6).
So I have created a slightly cut-down (no database involved) complete
working program. Can you see if this works ok with your version of
formlets:
module Main where
import Control.Applicative
import Control.Applicative.Error
import Control.Applicative.State
import Data.List as List
import Text.Formlets
import qualified Text.XHtml.Strict.Formlets as F
import qualified Text.XHtml.Strict as X
import Text.XHtml.Strict ((+++), ())
import Happstack.Server
type XForm a = F.XHtmlForm IO a
data Registration = Registration { regUser :: String
, regPass :: String }
deriving Show
handleRegistration :: ServerPartT IO Response
handleRegistration = withForm register register showErrorsInline (\u -
okHtml $ regUser u ++ is successfully registered)
withForm :: String - XForm a - (X.Html - [String] - ServerPartT IO
Response) - (a - ServerPartT IO Response) - ServerPartT IO Response
withForm name frm handleErrors handleOk = dir name $ msum
[ methodSP GET $ createForm [] frm = okHtml
, withDataFn lookPairs $ \d -
methodSP POST $ handleOk' $ simple d
]
where
handleOk' d = do
let (extractor, html, _) = runFormState d frm
v - liftIO extractor
case v of
Failure faults - do
f - createForm d frm
handleErrors f faults
Success s - handleOk s
simple d = List.map (\(k,v) - (k, Left v)) d
showErrorsInline :: X.Html - [String] - ServerPartT IO Response
showErrorsInline renderedForm errors =
okHtml $ X.toHtml (show errors) +++ renderedForm
createForm :: Env - XForm a - ServerPartT IO X.Html
createForm env frm = do
let (extractor, xml, endState) = runFormState env frm
xml' - liftIO xml
return $ X.form X.! [X.method POST] (xml' +++ X.submit submit Submit)
okHtml :: (X.HTML a) = a - ServerPartT IO Response
okHtml content = ok $ toResponse $ htmlPage $ content
htmlPage :: (X.HTML a) = a - X.Html
htmlPage content = (X.header (X.thetitle Testing forms))
+++ (X.body content)
register :: XForm Registration
register = Registration $ user * passConfirmed
user :: XForm String
user = pure_user `F.checkM` F.ensureM valid error where
valid name = return True
error = Username already exists in the database!
pure_user :: XForm String
pure_user = input `F.check` F.ensure valid error where
input = Username `label` F.input Nothing
valid = (= 3) . length
error = Username must be three characters or longer.
passConfirmed :: XForm String
passConfirmed = fst $ passwords `F.check` F.ensure equal error where
passwords = (,) $ pass Password * pass Password (confirm)
equal (a, b) = a == b
error = The entered passwords do not match!
pass :: String - XForm String
pass caption = input `F.check` F.ensure valid error where
input = caption `label` F.password Nothing
valid = (=6) . length
error = Password must be six characters or longer.
label :: String - XForm String - XForm String
label l = F.plug (\xhtml - X.p (X.label (l ++ : ) +++ xhtml))
main = simpleHTTP (nullConf {port = 9959}) handleRegistration
--
Colin Adams
Preston Lancashire
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Re: [Haskell-cafe] Problem with monadic formlets
Colin == Colin Paul Adams co...@colina.demon.co.uk writes: Jeremy == Jeremy Shaw jer...@n-heptane.com writes: Colin apparent data corruprion is occurring. I am suspecting a Colin bug in the formlets library (I have version 0.6). Colin So I have created a slightly cut-down (no database Colin involved) complete working program. Can you see if this Colin works ok with your version of formlets: I managed to uninstall formlets-0.6 myself, and then installed 0.5 instead. After adding the necessary extra argument to runFormletState (an empty string), the test program works fine. So this seems to be a bug in formlets-0.6. -- Colin Adams Preston Lancashire ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Problem with monadic formlets
I'm trying to validate user input against a database (using HaskellDB, but that doesn't seem to be the problem, as replacing the database monadic code with return True gives the same problem. This is part of my code: register :: Database - XForm Registration --register db = Registration $ pure_user * passConfirmed register db = Registration $ (user db) * passConfirmed user :: Database - XForm String user db = pure_user `F.checkM` F.ensureM valid error where valid name = do let q = do t - table user_table restrict (t!user_name .==. constant name) return t rs - query db q return $ null rs error = Username already exists in the database! pure_user :: XForm String pure_user = input `F.check` F.ensure valid error where input = Username `label` F.input Nothing valid = (= 3) . length error = Username must be three characters or longer. passConfirmed :: XForm String passConfirmed = fst $ passwords `F.check` F.ensure equal error where passwords = (,) $ pass Password * pass Password (confirm) equal (a, b) = a == b error = The entered passwords do not match! pass :: String - XForm String pass caption = input `F.check` F.ensure valid error where input = caption `label` F.password Nothing valid = (=6) . length error = Password must be six characters or longer. If I uncomment the commented line, and comment out the line after it (in register), then everything works as expected. However, using it as it is, one of the calls to pass gets the user's name for validation (and consequently either fails if the user name is only 5 characters, or the comparison of the two passwords fail (unless I type the user name as the password). I thought the applicative style meant the effects did not influence one another, but here there is clear contamination. What am i doing wrong? -- Colin Adams Preston Lancashire ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Problem with monadic formlets
Hello, I hacked your code into a runnable example, and it seems to work for me. What happens if you do something like: let (c, xml, _) = runFormState [(input0,Left name), (input1, Left password), (input2, Left password) ] (register foo) in c = \r - do print xml print r (except you need to pass in a Database instead of foo as the argument to register.) I get: label Username/label input type=text name=input0 id=input0 value=name /label Password/label input type=password name=input1 id=input1 value=password /label Password (confirm)/label input type=password name=input2 id=input2 value=password / Success (Registration name password) Which looks correct to me. Your code looks fine to me as well... Perhaps the error is not in the code you pasted, but somewhere else. I am running on an older, and somewhat forked version of Formlets, so there could also be a bug in the new code I guess. Though, that seems unlikely. But it is worth noting that we are not using the same version of the formlets library. - jeremy At Thu, 27 Aug 2009 16:09:18 +0100, Colin Paul Adams wrote: I'm trying to validate user input against a database (using HaskellDB, but that doesn't seem to be the problem, as replacing the database monadic code with return True gives the same problem. This is part of my code: register :: Database - XForm Registration --register db = Registration $ pure_user * passConfirmed register db = Registration $ (user db) * passConfirmed user :: Database - XForm String user db = pure_user `F.checkM` F.ensureM valid error where valid name = do let q = do t - table user_table restrict (t!user_name .==. constant name) return t rs - query db q return $ null rs error = Username already exists in the database! pure_user :: XForm String pure_user = input `F.check` F.ensure valid error where input = Username `label` F.input Nothing valid = (= 3) . length error = Username must be three characters or longer. passConfirmed :: XForm String passConfirmed = fst $ passwords `F.check` F.ensure equal error where passwords = (,) $ pass Password * pass Password (confirm) equal (a, b) = a == b error = The entered passwords do not match! pass :: String - XForm String pass caption = input `F.check` F.ensure valid error where input = caption `label` F.password Nothing valid = (=6) . length error = Password must be six characters or longer. If I uncomment the commented line, and comment out the line after it (in register), then everything works as expected. However, using it as it is, one of the calls to pass gets the user's name for validation (and consequently either fails if the user name is only 5 characters, or the comparison of the two passwords fail (unless I type the user name as the password). I thought the applicative style meant the effects did not influence one another, but here there is clear contamination. What am i doing wrong? -- Colin Adams Preston Lancashire ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
