+{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TypeFamilies #-}
-- | General XML stuff.
--
module Xml (
+ Child(..),
DtdName(..),
FromXml(..),
+ FromXmlFk(..),
+ ToDb(..),
parse_opts,
+ parse_opts_novalidate,
pickle_unpickle,
- unpickleable )
+ unpickleable,
+ unsafe_read_document,
+ unsafe_read_invalid_document,
+ unsafe_unpickle )
where
+-- System imports.
import Control.Exception ( SomeException(..), catch )
+import Database.Groundhog.Core ( PersistEntity(..) )
import Text.XML.HXT.Core (
(>>>),
(/>),
PU,
SysConfigList,
- XmlPickler(..),
- hasName,
+ XmlTree,
+ isElem,
+ no,
readDocument,
runX,
withRemoveWS,
+ withSubstDTDEntities,
+ withValidate,
xpickleVal,
+ xunpickleDocument,
xunpickleVal,
yes )
--- | A typeclass for XML types that can be converted into an associated
--- database type. The story behind this is long, but basically, we need
--- to different types for each XML thingie we're going to import: a
--- database type and an XML type. Both Groundhog and HXT are very
--- particular about the types that they can use, and there's no way
--- to reuse e.g. a type that HXT can pickle in Groundhog. So this
--- typeclass gives us a way to get the database type from the XML
--- type that we have to define for HXT.
+
+-- | Common associated type shared by 'FromXml' and 'FromXmlFk'. This
+-- basically just forces the client to define the \"database
+-- version\" of his type.
--
-class FromXml a where
- -- | Each instance a must declare its associated database type (Db a)
+class ToDb a where
+ -- | Each instance @a@ must declare its associated database type @Db a@.
type Db a :: *
- -- | And provide a function for getting a (Db a) out of an "a".
+-- | A typeclass for XML types that can be converted into an
+-- associated database type. The story behind this is long, but
+-- basically, we need to different types most XML thingies we're
+-- going to import: a database type and an XML type.
+--
+-- Both Groundhog and HXT are very particular about the types that
+-- they can use, and there's no way to reuse e.g. a type that HXT
+-- can pickle in Groundhog. This typeclass gives us a standard way
+-- to get the database type from the XML type that we have to define
+-- for HXT.
+--
+class (ToDb a) => FromXml a where
+ -- | A function for getting a @Db a@ out of an @a@.
from_xml :: a -> Db a
--- | Represents the DTD filename ("SYSTEM") part of the DOCTYPE
+-- | A class for XML representations which are children of other
+-- elements. The foal is to associate a child XML element with its
+-- parent element's database type. This is required to construct the
+-- database analogue of @a@ in 'FromXmlFk'.
+--
+class Child a where
+ -- | The type of our parent object, i.e. to the type to whom our
+ -- foreign key will point.
+ type Parent a :: *
+
+
+-- | Some database types cannot be constructed from the XML type
+-- alone; they must be supplied a foreign key to a parent object
+-- first. Members of this class can be converted from an XML
+-- representation to a database representation in this manner.
+--
+class (Child a, ToDb a) => FromXmlFk a where
+ -- | The function that produces a @Db a@ out of a foreign key and an
+ -- @a@. The parameter order makes it easier to map this function
+ -- over a bunch of things.
+ from_xml_fk :: DefaultKey (Parent a) -> a -> Db a
+
+
+
+-- | Represents the DTD filename (\"SYSTEM\") part of the DOCTYPE
-- definition.
newtype DtdName = DtdName String
-- | A list of options passed to 'readDocument' when we parse an XML
-- document. All cosmetic whitespace should be removed, otherwise we
--- have to parse it in each pickler.
+-- would have to parse whitespace in each (un)pickler.
--
parse_opts :: SysConfigList
-parse_opts = [ withRemoveWS yes ]
+parse_opts = [ withRemoveWS yes,
+ withSubstDTDEntities no ]
+-- | Like 'parse_opts' except we don't validate the document against
+-- its DTD. This is useful when we need to parse a document that we
+-- /know/ is invalid so that we can deliver a better error message.
+--
+parse_opts_novalidate :: SysConfigList
+parse_opts_novalidate = (withValidate no) : parse_opts
--- | Given a root element name and a file path, return both the
--- original unpickled root "object" and the one that was constructed
--- by pickled and unpickling the original. This is used in a number
--- of XML tests which pickle/unpickle and then make sure that the
--- output is the same as the input.
+
+-- | Given an @unpickler@ and a @filepath@, attempt to unpickle the
+-- root element of @filepath@ using @unpickler@ and return both the
+-- original unpickled object and one constructed by pickling and
+-- unpickling that original. This is used in a number of XML tests
+-- which pickle/unpickle and then make sure that the output is the
+-- same as the input.
--
-- We return the object instead of an XmlTree (which would save us
-- an unpickle call) because otherwise the type of @a@ in the call
-- before/after results from this function agree does not mean that
-- the document was successfully unpickled!
--
-pickle_unpickle :: XmlPickler a
- => String
- -> FilePath
+pickle_unpickle :: PU a -- ^ @unpickler@ returning an @a@
+ -> FilePath -- ^ Path to the document to unpickle.
-> IO ([a], [a])
-pickle_unpickle root_element filepath = do
+pickle_unpickle unpickler filepath = do
-- We need to check only the root message element since
-- readDocument produces a bunch of other junk.
expected <- runX arr_getobj
actual <- runX $ arr_getobj
>>>
- xpickleVal xpickle
+ xpickleVal unpickler
>>>
- xunpickleVal xpickle
+ xunpickleVal unpickler
return (expected, actual)
where
arr_getobj = readDocument parse_opts filepath
/>
- hasName root_element
+ isElem -- Drop the extra junk readDocument pulls in.
>>>
- xunpickleVal xpickle
+ xunpickleVal unpickler
-- would result. By taking the unpickler as an argument, we allow
-- the caller to indirectly specify a concrete type.
--
-unpickleable :: XmlPickler a => FilePath -> PU a -> IO Bool
+-- Apologies the the name; unpickleable means \"we can unpickle
+-- it\", not \"not pickleable.\"
+--
+unpickleable :: FilePath -> PU a -> IO Bool
unpickleable filepath unpickler = do
xmldoc <- try_unpickle `catch` (\(SomeException _) -> return [])
return $ (not . null) xmldoc
try_unpickle = runX $ readDocument parse_opts filepath
>>>
xunpickleVal unpickler
+
+
+-- | Unpickle from a 'FilePath' using the given pickler. Explode if it
+-- doesn't work.
+--
+unsafe_unpickle :: FilePath -> PU a -> IO a
+unsafe_unpickle filepath unpickler =
+ fmap head $ runX $ xunpickleDocument unpickler parse_opts filepath
+
+
+-- | Read an XML document from a 'FilePath' into an XmlTree. Explode if it
+-- doesn't work.
+--
+unsafe_read_document :: FilePath -> IO XmlTree
+unsafe_read_document filepath =
+ fmap head $ runX $ readDocument parse_opts filepath
+
+-- | The same as 'unsafe_read_document', except it allows you to read
+-- documents which don't validate against their DTDs.
+--
+unsafe_read_invalid_document :: FilePath -> IO XmlTree
+unsafe_read_invalid_document filepath =
+ fmap head $ runX $ readDocument parse_opts_novalidate filepath
projects / dead / htsn-import.git / blobdiff