July 2011 - web-devel

"Wiki" section of the Yesod doc site
by Michael Snoyman 13 May '12

13 May '12

Hi everyone, I've added a new section to the Yesod doc site: the wiki[1]. This section is intended to be user-writable, so if you have any content you'd like to submit, please go ahead. In particular, this section contains the "Powered by Yesod" page: please add your sites. Unfortunately, the list from the old wiki was lost when my previous VPS died. (All my databases were backed up, I just forgot to backup the Wiki content as well...) Michael [1] http://www.yesodweb.com/page/wiki

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[ Newbie ] [ MongoDB ] Using MongoDB Persistent backend
by Kamil Ciemniewski 03 Aug '11

03 Aug '11

Hi all, I've got some "newbie" problems using MongoDB as backend in Persistent. Basically I've got my app type defined as: data MyApp = MyApp { getStatic :: Static -- ^ Settings for static file serving. , connPool :: ConnPool Host } And I made it an instance of YesodPersist by: instance YesodPersist MyApp where type YesodDB MyApp = MongoDBReader Host runDB db = liftIOHandler $ fmap connPool getYesod >>= (\p -> return (p, "localhost")) >>= runMongoDBConn db And I made it an instance of YesodAuth as well by: instance YesodAuth MyApp where type AuthId MyApp = UserId loginDest _ = RootR logoutDest _ = RootR getAuthId creds = runDB $ do x <- getBy $ UniqueUser $ credsIdent creds case x of Just (uid, _) -> return $ Just uid Nothing -> do fmap Just $ insert $ User (credsIdent creds) Nothing authPlugins = [ authEmail ] I've defined User model as yesod scaffold tool defines it. Now, when I try to compile it i get: No instances for (Control.Monad.Context.Context Database.MongoDB.Connection.MasterOrSlaveOk (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.Database (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Internal.Protocol.Pipe (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.WriteMode (GGHandler s MyApp IO), Control.Monad.Throw.Throw Database.MongoDB.Query.Failure (GGHandler s MyApp IO)) arising from a use of `insert' Possible fix: add instance declarations for (Control.Monad.Context.Context Database.MongoDB.Connection.MasterOrSlaveOk (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.Database (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Internal.Protocol.Pipe (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.WriteMode (GGHandler s MyApp IO), Control.Monad.Throw.Throw Database.MongoDB.Query.Failure (GGHandler s MyApp IO)) In the expression: insert In the second argument of `($)', namely `insert $ User (credsIdent creds) Nothing' In the expression: fmap Just $ insert $ User (credsIdent creds) Nothing The problem is probably very trivial.. But I've got no ideas how to fix it. Best regards Kamil Ciemniewski

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Question about changes in Yesod.Form.Fields
by Michael Litchard 30 Jul '11

30 Jul '11

I appreciate the additional functionality that allows multi select fields. The interface to selectField has changed however. The following code used to work. I cannot make sense of the changes, and couldn't find any use examples in the source. Could someone lend a hand and tell me how the following should be re-written? sslvpnForm = fixType $ runFormPost $ renderDivs $ pure (,) <*> areq (multiSelectField servers) "Pick some servers" Nothing <*> areq (selectField tests) "Pick a test" Nothing

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[Newbie][Parsec] Skipping to desired phrase
by Kamil Ciemniewski 29 Jul '11

29 Jul '11

Hi all, I've got a String containing html and I'd like to extract from it some informations.. Specifically these informations start at point "after" some phrase ( let say "nicelinks"). How do I skip all the html up to the point of this phrase? I've done that much already: p_rest = do skipMany ((try (string "nicelinks")) <|> anyHeadString) text <- many1 anyChar return [text] anyHeadString = do c <- anyChar return [c] But after doing: parse p_rest [] html I get: Left (line 112, column 15): unexpected end of input expecting "nicelinks" What am I doing wrong? Best regards

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libstdc++ missing during yesod installation on OS X
by Alexandros Salazar 28 Jul '11

28 Jul '11

Hi all, I tried installing the haskell platform and yesod from scratch, but it failed during the installation of double-conversion-0.2.0.0 with the following error: Loading package double-conversion-0.2.0.0 ... <command line>: can't load .so/.DLL for: stdc++ (dlopen(libstdc++.dylib, 9): image not found) cabal: Error: some packages failed to install: yesod-auth-0.6.0 failed during the building phase. The exception was: ExitFailure 1 I am running Snow Leopard 10.6.8. Has anyone run into this problem? Did you figure out how to avoid it/work around it? It seems it has something to do with libstdc++ being statically linked on OS X, but I can't figure out the details. Thanks, Alexandros

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Upgrade to Happstack 6 - request bodies
by Sebastiaan Visser 28 Jul '11

28 Jul '11

Hello all, We have some problems upgrading one of our server applications to Happstack 6, lots of things related to request bodies and request parameters have changed. Unfortunately, the new situation doesn't seem that straightforward to me. In the previous version of Happstack we were able to access the request body directly using the `rqBody` function. In the new situation we have to first decode the body using `decodeBody` and than access it by reading from an MVar. The utility functions accessing this variables ensure the body is only request once, all consecutive calls will error. We're pretty sure we're accessing the body only once and after decoding it, but we still get the following error: "askRqEnv failed because the request body has not been decoded yet. Try using 'decodeBody'." This happens when accessing the cookie using 'readCookieValue'. Isn't strange that accessing the cookie value uses the request body at all? So the pattern we use is: > do decodeBody (defaultBodyPolicy "/tmp/" (10 * 1024 * 1024) (10 * 1024 * 1024) (1024 * 1024)) > liftIO (print 1) > c <- lookCookieValue "tid" > liftIO (print 2) > b <- takeRequestBody > ... And the result is: > 1 > askRqEnv failed because the request body has not been decoded yet. Try using 'decodeBody'. (this happens using happstack-server-6.0.3, in 6.1.6 the same error string is sent to the client) And then it stops, the handler crashes and the request fails. The migration guide[1] tells me "To simulate the old behavior, simple call decodeBody in your top-level handler for every request.", but this is clearly not enough. Anyone knows how to fix this in the correct way? I cannot help to think it is a bit strange that it takes me so much time to convince a web framework to hand me over the request body. This should be easy stuff right? Thanks, Sebastiaan [1] http://code.google.com/p/happstack/wiki/Happstack6Migration

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considering ecommerce options
by Eric Rasmussen 27 Jul '11

27 Jul '11

Hi everyone, Apologies in advance if this is slightly off-topic, but I'm looking into a long-term development solution for ecommerce projects (primarily an online storefront/checkout system), and I am wondering what others on this list are using. I'm most interested in any Haskell advances in this area, but at this point I'd appreciate non-Haskell recommendations too. My hope is that if it's something a Haskell developer finds tolerable to work with, it's a step up from the systems I've been testing so far, and if there is anything being worked on in Haskell that's even better. Thanks! Eric

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Failed to compile authenticate
by Haisheng Wu 24 Jul '11

24 Jul '11

Hello, Sorry if I supposed to post question to Google group which is not available at my current region unfortunately. My question comes I failed to compile package authenticate-0.9.1.7 with error below. Do you have any ideas about fixing it? Please let me if you need further environment information. Thanks! simonwu@ubuntu:~/haskell/authenticate$ cabal build Preprocessing library authenticate-0.9.1.7... Building authenticate-0.9.1.7... [ 8 of 10] Compiling OpenId2.Discovery ( OpenId2/Discovery.hs, dist/build/OpenId2/Discovery.o ) OpenId2/Discovery.hs:137:18: No instance for (Text.StringLike.StringLike Text) arising from a use of `parseTags' at OpenId2/Discovery.hs:137:18-26 Possible fix: add an instance declaration for (Text.StringLike.StringLike Text) In the second argument of `(.)', namely `parseTags' In the second argument of `(.)', namely `mapMaybe linkTag . parseTags' In the second argument of `(.)', namely `filter isOpenId . mapMaybe linkTag . parseTags' simonwu@ubuntu:~/haskell/authenticate$ ghci --version The Glorious Glasgow Haskell Compilation System, version 6.12.3 -Haisheng

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Re: [web-devel] [Haskell] ANN: boomerang and web-routes-boomerang
by Jeremy Shaw 21 Jul '11

21 Jul '11

Nope. It is not related. It is also not related to the GSM library: http://www.programmersheaven.com/download/29760/download.aspx or the decompiler: http://boomerang.sourceforge.net/index.php Perhaps picking an original name would have been a wise choice. But it was the only I idea I had :) I am only inclined to change it if there is a strong chance of people wanting to use the boomerang name on hackage to refer to something related to the harmony boomerang project.. - jeremy On Thu, Jul 21, 2011 at 1:55 PM, Janis Voigtländer <jv(a)informatik.uni-bonn.de> wrote: > Am 21.07.2011 20:45, schrieb Jeremy Shaw: >> >> Hello, >> >> I am pleased to announce the release of two new libraries: boomerang >> and web-routes-boomerang. > > Does this have anything to do with: > > "Boomerang: A bidirectional programming language for ad-hoc data" > http://www.seas.upenn.edu/~harmony/ > > ? > > If not, is it wise to name it thus? > > Wondering, > Janis. > > -- > Jun.-Prof. Dr. Janis Voigtländer > http://www.iai.uni-bonn.de/~jv/ > mailto:jv@iai.uni-bonn.de >

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ANN: boomerang and web-routes-boomerang
by Jeremy Shaw 21 Jul '11

21 Jul '11

Hello, I am pleased to announce the release of two new libraries: boomerang and web-routes-boomerang. boomerang is a library for general purpose, invertible parsing and pretty printing. It provides combinators which allow you to specify a grammar once and automatically extract a parser and pretty-printer from it. This library was refactored, with permission, from the Zwaluw library created by Sjoerd Visscher and Martijn van Steenbergen. hackage: http://hackage.haskell.org/package/boomerang quick intro: http://hackage.haskell.org/packages/archive/boomerang/1.0.0/doc/html/Text-B… web-route-boomerang provides glue code for using boomerang with web-routes. web-routes is a framework-independent, type-safe, url routing library. hackage: http://hackage.haskell.org/package/web-routes-boomerang tutorial: http://happstack.com/docs/crashcourse/WebRoutes.html#web-routes-boomerang - jeremy p.s. boomerang is similar in purpose to the inveritble-syntax library: http://hackage.haskell.org/package/invertible-syntax The libraries take different approaches and are both worth considering.

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