Deserializing to Markdown fails because a PersistByteString is passed

[MaxGabriel]

It looks like yesod-text-markdown isn't able to deserialize what was inserted; fromPersistValue is passed a PersistByteString when yesod-text-markdown requires a PersistText. This can be reproduced like so :

1. Create a new scaffolded MySQL project (I used yesod-bin 1.4.13.3)

2. Add the markdown and yesod-text-markdown packages to build-depends in the Cabal file (I used the versions from LTS Haskell 2.17).

3. Add these imports to Model.hs:

   import Text.Markdown (Markdown)
   import Yesod.Text.Markdown ()

4. Add this model to config/models:

   BlogPost
       title Text
       article Markdown
   

5. Start a GHCi session and run the following code:

   ghci > db $ insert (BlogPost "title" "article")
   ghci > import Database.Persist.Sql
   ghci > db $ get (toSqlKey 1 :: BlogPostId)
   14/Aug/2015:08:49:59 -0700 [Debug#SQL] SELECT `title`,`article` FROM `blog_post` WHERE `id`=?; [PersistInt64 1]
   *** Exception: runFakeHandler issue: InternalError "get BlogPostKey {unBlogPostKey = SqlBackendKey {unSqlBackendKey = 1}}: field article: Not a PersistText value"
   

(I think this can be reproduced easily in a script/test; I'll try to write one up)

These two StackOverflow questions reported the issue:

• http://stackoverflow.com/questions/31898691/storing-markdown-in-a-yesod-persist-model#
• http://stackoverflow.com/questions/31902061/what-does-not-a-persisttext-value-mean

This might be a bug in Persistent; I'm still investigating.

[Tarrasch]

Thanks for creating the issue. It was so long time ago I used Yesod though, I think you'll have to investigate on your own :-/.

Anyway, I'm happy to merge PRs and upload fixes :)

[MaxGabriel]

@Tarrasch No problem