- web-devel - Haskell.org

[Persistent] PersistBackend and the ErrorT monad
by Max Cantor 24 Aug '11

24 Aug '11

Hi, I am trying to use an ErrorT monad inside some Persist code. I wrote the following instance: newtype OcrError = OE String ... instance PersistBackend m => PersistBackend (ErrorT OcrError m) where replace k v = lift $ replace k v update k l = lift $ update k l updateWhere f u = lift $ updateWhere f u delete = lift . delete insert = lift . insert deleteBy = lift . deleteBy deleteWhere = lift . deleteWhere get = lift . get getBy = lift . getBy count = lift . count selectKeys f = selectKeys f selectEnum f o lim off = selectEnum f o lim off It seems like there is a problem with selectEnum though. In GHCI, this: l :: [PersistKV OcrRefMap] <- rs $ selectEnum [] [] 0 0 works fine, while this: l :: Either OcrError [PersistKV OcrRefMap] <- rs $ runErrorT $ selectEnum [] [] 0 0 hangs. rs is a small function to run persist calls: rs :: (MonadControlIO m) => SqlPersist m a -> m a rs f = do let conn = DT.pack "user=hachicode password=password host=localhost port=5432 dbname=hachicode" withPostgresqlConn conn $ runSqlConn f and you need -XScopedTypeVariables for the ghci commands. Any advice? Thanks, Max

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Re: [web-devel] Caching the System time
by Aristid Breitkreuz 22 Aug '11

22 Aug '11

Did you measure how long it takes to generate that datetime string? Shouldn't that be possible in a hundred nanoseconds or so? Am 08.08.2011 15:01 schrieb "Gregory Collins" <greg(a)gregorycollins.net>:

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wai-logger
by Kazu Yamamoto 22 Aug '11

22 Aug '11

Hello, Sorry for the delay but I have released wai-logger: http://hackage.haskell.org/package/wai-logger I provide low level modules and a high level module. Users should use the low level modules. The high level module is designed for Mighttpd which uses the prefork technique. A sample code is found in its module documentation. Please use this package and give me feedback. And let's consider how to make this as a WAI middle ware. --Kazu

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wai/wai-handler-devel
by Kazu Yamamoto 17 Aug '11

17 Aug '11

Hello, Since I cannot found a way to send a message to yesodweb on GitHub, I'm writhing here. Please advice me if there is another right place. wai/wai-handler-devel has following files: TestApp.hs Testapp.hs testapp.hs I cloned the repository to Mac. Since the default file system of Mac is case-insensitive for file names, the three files are treated as the same and testapp.hs overwrote the others. It would be appreciated if their names will be unique for Mac. --Kazu

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Re: [web-devel] [hakyll] Users of Hamlet templates in Hakyll
by Jasper Van der Jeugt 14 Aug '11

14 Aug '11

> Michael is on vacation for a few days, but he can better answer about runtime support. Good point! > What is the Hamlet templating? Is this the $description$ and $title$ > stuff in the HTML skeleton files? If it is, I am most certainly using > it! No, those are the Hakyll templates (which is more or less the default). The Hamlet templates are an extension which allows you to use a HAML-like syntax in templates. You enable them by using `.hamlet` templates instead of `.html` templates -- I'm sorry if I caused any confusion. Cheers, Jasper

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Users of Hamlet templates in Hakyll
by Jasper Van der Jeugt 13 Aug '11

13 Aug '11

Hello all, I've been thinking of powering up the template system in Hakyll a bit lately. However, the current support for Hamlet templates makes this a hard task. I was even thinking of dropping Hamlet support entirely for two reasons: - the runtime bindings seem to be available no more in the latest release of hamlet, making Hakyll dependent on an older Hamlet version; - the mismatches between the two formats. Obviously, I don't want to break any sites, so I would like to hear if anyone is currently using this feature, and what their opinions are. Cheers, Jasper

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A logging system as a WAI middleware
by Kazu Yamamoto 10 Aug '11

10 Aug '11

Hello, Greg Weber asked me to implement a logging system as a WAI middleware. So, I considered it. The typical Apache log format is as follows: 127.0.0.1 - - [10/Aug/2011:11:27:34 +0900] "GET / HTTP/1.1" 200 512 "referer" "agent" where 200 is status and 512 is a response size Response is defined as follows: ResponseFile Status ResponseHeaders FilePath (Maybe FilePart) ResponseBuilder Status ResponseHeaders Builder ResponseEnumerator (forall a. ResponseEnumerator a) We cannot know status from ResponseEnumerator. Also, we cannot directly know size from the all three. Design choices are as follows: 1) Modified the Response type and implement a logging system as a WAI middleware. 2) Giving up implementing a logging system as a WAI middleware and implement a logging system as just a library. Which one is better? --Kazu

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Announce: xss-sanitize 0.3: css styles allowed
by Greg Weber 09 Aug '11

09 Aug '11

xss-sanitize is a library that allows you to accept html from untrusted sources by first filtering it through a white list. For example, this allows a web application to safely use a rich text editor or allow html in comments. version 0.3 allows elements to have a style attribute. The css will be parsed and ran through a special css white list. This new version adds a dependency on attoparsec-text This library is used automatically and transparently in Yesod where appropriate, and the new version will be used in the upcoming 0.9 release.

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Caching the System time
by Greg Weber 08 Aug '11

08 Aug '11

Helllo Snap maintainers! We are finally getting around to implementing a robust logging solution within Yesod. This creates the issue of having to frequently access the system time. I see that Snap has a separate thread to get the system time and cache the result [1]. Are you happy with this implementation? Can it be placed in a separate package and shared between web frameworks? Thanks, Greg Weber [1] http://hackage.haskell.org/packages/archive/snap-server/0.2.2/doc/html/src/…

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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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