Safe Haskell | None |
---|---|
Language | Haskell98 |
This module provides both a native Haskell solution for parsing XML documents into a stream of events, and a set of parser combinators for dealing with a stream of events.
As a simple example, if you have the following XML file:
<?xml version="1.0" encoding="utf-8"?> <people> <person age="25">Michael</person> <person age="2">Eliezer</person> </people>
Then this code:
{-# LANGUAGE OverloadedStrings #-} import Control.Monad.Trans.Resource import Data.Conduit (Consumer, Sink, ($$)) import Data.Text (Text, unpack) import Text.XML.Stream.Parse import Data.XML.Types (Event) data Person = Person Int Text deriving Show parsePerson :: MonadThrow m => Consumer Event m (Maybe Person) parsePerson = tag' "person" (requireAttr "age") $ \age -> do name <- content return $ Person (read $ unpack age) name parsePeople :: MonadThrow m => Sink Event m (Maybe [Person]) parsePeople = tagNoAttr "people" $ many parsePerson main = do people <- runResourceT $ parseFile def "people.xml" $$ force "people required" parsePeople print people
will produce:
[Person 25 "Michael",Person 2 "Eliezer"]
This module also supports streaming results using yield
.
This allows parser results to be processed using conduits
while a particular parser (e.g. many
) is still running.
Without using streaming results, you have to wait until the parser finished
before you can process the result list. Large XML files might be easier
to process by using streaming results.
See http://stackoverflow.com/q/21367423/2597135 for a related discussion.
{-# LANGUAGE OverloadedStrings #-} import Control.Monad (void) import Control.Monad.Trans.Class (lift) import Control.Monad.Trans.Resource import Data.Conduit import qualified Data.Conduit.List as CL import Data.Text (Text, unpack) import Data.XML.Types (Event) import Text.XML.Stream.Parse data Person = Person Int Text deriving Show parsePerson :: MonadThrow m => Consumer Event m (Maybe Person) parsePerson = tag' "person" (requireAttr "age") $ \age -> do name <- content return $ Person (read $ unpack age) name parsePeople :: MonadThrow m => Conduit Event m Person parsePeople = void $ tagNoAttr "people" $ manyYield parsePerson main = runResourceT $ parseFile def "people.xml" $$ parsePeople =$ CL.mapM_ (lift . print)
Previous versions of this module contained a number of more sophisticated functions written by Aristid Breitkreuz and Dmitry Olshansky. To keep this package simpler, those functions are being moved to a separate package. This note will be updated with the name of the package(s) when available.
- parseBytes :: MonadThrow m => ParseSettings -> Conduit ByteString m Event
- parseBytesPos :: MonadThrow m => ParseSettings -> Conduit ByteString m EventPos
- parseText' :: MonadThrow m => ParseSettings -> Conduit Text m Event
- parseText :: MonadThrow m => ParseSettings -> Conduit Text m EventPos
- parseTextPos :: MonadThrow m => ParseSettings -> Conduit Text m EventPos
- detectUtf :: MonadThrow m => Conduit ByteString m Text
- parseFile :: MonadResource m => ParseSettings -> FilePath -> Producer m Event
- parseLBS :: MonadThrow m => ParseSettings -> ByteString -> Producer m Event
- data ParseSettings
- def :: Default a => a
- type DecodeEntities = Text -> Content
- type DecodeIllegalCharacters = Int -> Maybe Char
- psDecodeEntities :: ParseSettings -> DecodeEntities
- psDecodeIllegalCharacters :: ParseSettings -> DecodeIllegalCharacters
- psRetainNamespaces :: ParseSettings -> Bool
- decodeXmlEntities :: DecodeEntities
- decodeHtmlEntities :: DecodeEntities
- tag :: MonadThrow m => NameMatcher a -> (a -> AttrParser b) -> (b -> ConduitM Event o m c) -> ConduitM Event o m (Maybe c)
- tag' :: MonadThrow m => NameMatcher a -> AttrParser b -> (b -> ConduitM Event o m c) -> ConduitM Event o m (Maybe c)
- tagNoAttr :: MonadThrow m => NameMatcher a -> ConduitM Event o m b -> ConduitM Event o m (Maybe b)
- tagIgnoreAttrs :: MonadThrow m => NameMatcher a -> ConduitM Event o m b -> ConduitM Event o m (Maybe b)
- content :: MonadThrow m => Consumer Event m Text
- contentMaybe :: MonadThrow m => Consumer Event m (Maybe Text)
- ignoreTag :: MonadThrow m => NameMatcher a -> ConduitM Event o m (Maybe ())
- ignoreEmptyTag :: MonadThrow m => NameMatcher a -> ConduitM Event o m (Maybe ())
- ignoreTree :: MonadThrow m => NameMatcher a -> ConduitM Event o m (Maybe ())
- ignoreTreeContent :: MonadThrow m => NameMatcher a -> ConduitM Event o m (Maybe ())
- ignoreAnyTreeContent :: MonadThrow m => ConduitM Event o m (Maybe ())
- ignoreAllTreesContent :: MonadThrow m => ConduitM Event o m (Maybe ())
- takeContent :: MonadThrow m => ConduitM Event Event m (Maybe ())
- takeTree :: MonadThrow m => NameMatcher a -> AttrParser b -> ConduitM Event Event m (Maybe ())
- takeTreeContent :: MonadThrow m => NameMatcher a -> AttrParser b -> ConduitM Event Event m (Maybe ())
- takeAnyTreeContent :: MonadThrow m => ConduitM Event Event m (Maybe ())
- takeAllTreesContent :: MonadThrow m => ConduitM Event Event m (Maybe ())
- newtype NameMatcher a = NameMatcher {
- runNameMatcher :: Name -> Maybe a
- matching :: (Name -> Bool) -> NameMatcher Name
- anyOf :: [Name] -> NameMatcher Name
- anyName :: NameMatcher Name
- data AttrParser a
- attr :: Name -> AttrParser (Maybe Text)
- requireAttr :: Name -> AttrParser Text
- optionalAttr :: Name -> AttrParser (Maybe Text)
- requireAttrRaw :: String -> ((Name, [Content]) -> Maybe b) -> AttrParser b
- optionalAttrRaw :: ((Name, [Content]) -> Maybe b) -> AttrParser (Maybe b)
- ignoreAttrs :: AttrParser ()
- orE :: Monad m => Consumer Event m (Maybe a) -> Consumer Event m (Maybe a) -> Consumer Event m (Maybe a)
- choose :: Monad m => [ConduitM Event o m (Maybe a)] -> ConduitM Event o m (Maybe a)
- many :: Monad m => ConduitM Event o m (Maybe a) -> ConduitM Event o m [a]
- many_ :: MonadThrow m => ConduitM Event o m (Maybe a) -> ConduitM Event o m ()
- manyIgnore :: Monad m => ConduitM Event o m (Maybe a) -> ConduitM Event o m (Maybe b) -> ConduitM Event o m [a]
- many' :: MonadThrow m => ConduitM Event o m (Maybe a) -> ConduitM Event o m [a]
- force :: MonadThrow m => String -> m (Maybe a) -> m a
- manyYield :: Monad m => ConduitM a b m (Maybe b) -> Conduit a m b
- manyYield' :: MonadThrow m => ConduitM Event b m (Maybe b) -> Conduit Event m b
- manyIgnoreYield :: MonadThrow m => ConduitM Event b m (Maybe b) -> ConduitM Event b m (Maybe ()) -> Conduit Event m b
- data XmlException
- = XmlException { }
- | InvalidEndElement Name (Maybe Event)
- | InvalidEntity String (Maybe Event)
- | MissingAttribute String
- | UnparsedAttributes [(Name, [Content])]
- data PositionRange :: *
- type EventPos = (Maybe PositionRange, Event)
Parsing XML files
parseBytes :: MonadThrow m => ParseSettings -> Conduit ByteString m Event Source #
Parses a byte stream into Event
s. This function is implemented fully in
Haskell using attoparsec-text for parsing. The produced error messages do
not give line/column information, so you may prefer to stick with the parser
provided by libxml-enumerator. However, this has the advantage of not
relying on any C libraries.
This relies on detectUtf
to determine character encoding, and parseText'
to do the actual parsing.
parseBytesPos :: MonadThrow m => ParseSettings -> Conduit ByteString m EventPos Source #
parseText' :: MonadThrow m => ParseSettings -> Conduit Text m Event Source #
Parses a character stream into Event
s. This function is implemented
fully in Haskell using attoparsec-text for parsing. The produced error
messages do not give line/column information, so you may prefer to stick
with the parser provided by libxml-enumerator. However, this has the
advantage of not relying on any C libraries.
Since 1.2.4
parseText :: MonadThrow m => ParseSettings -> Conduit Text m EventPos Source #
Deprecated: Please use parseText'
or parseTextPos
.
parseTextPos :: MonadThrow m => ParseSettings -> Conduit Text m EventPos Source #
Same as parseText'
, but includes the position of each event.
Since 1.2.4
detectUtf :: MonadThrow m => Conduit ByteString m Text Source #
Automatically determine which UTF variant is being used. This function first checks for BOMs, removing them as necessary, and then check for the equivalent of <?xml for each of UTF-8, UTF-16LEBE, and UTF-32LEBE. It defaults to assuming UTF-8.
parseFile :: MonadResource m => ParseSettings -> FilePath -> Producer m Event Source #
A helper function which reads a file from disk using enumFile
, detects
character encoding using detectUtf
, parses the XML using parseBytes
, and
then hands off control to your supplied parser.
parseLBS :: MonadThrow m => ParseSettings -> ByteString -> Producer m Event Source #
Parse an event stream from a lazy ByteString
.
Parser settings
type DecodeEntities = Text -> Content Source #
psDecodeIllegalCharacters :: ParseSettings -> DecodeIllegalCharacters Source #
How to decode illegal character references (&#[0-9]+;
or &#x[0-9a-fA-F]+;
).
Character references within the legal ranges defined by the standard are automatically parsed. Others are passed to this function.
Default: const Nothing
Since 1.7.1
psRetainNamespaces :: ParseSettings -> Bool Source #
Whether the original xmlns attributes should be retained in the parsed values. For more information on motivation, see:
https://github.com/snoyberg/xml/issues/38
Default: False
Since 1.2.1
Entity decoding
decodeXmlEntities :: DecodeEntities Source #
Default implementation of DecodeEntities
, which leaves the
entity as-is. Numeric character references and the five standard
entities (lt, gt, amp, quot, pos) are handled internally by the
parser.
decodeHtmlEntities :: DecodeEntities Source #
HTML4-compliant entity decoder. Handles the additional 248 entities defined by HTML 4 and XHTML 1.
Note that HTML 5 introduces a drastically larger number of entities, and this code does not recognize most of them.
Event parsing
:: MonadThrow m | |
=> NameMatcher a | Check if this is a correct tag name
and return a value that can be used to get an |
-> (a -> AttrParser b) | Given the value returned by the name checker, this function will
be used to get an |
-> (b -> ConduitM Event o m c) | Handler function to handle the attributes and children
of a tag, given the value return from the |
-> ConduitM Event o m (Maybe c) |
The most generic way to parse a tag. It takes a NameMatcher
to check whether
this is a correct tag name, an AttrParser
to handle attributes, and
then a parser to deal with content.
Events
are consumed if and only if the tag name and its attributes match.
This function automatically absorbs its balancing closing tag, and will
throw an exception if not all of the attributes or child elements are
consumed. If you want to allow extra attributes, see ignoreAttrs
.
This function automatically ignores comments, instructions and whitespace.
tag' :: MonadThrow m => NameMatcher a -> AttrParser b -> (b -> ConduitM Event o m c) -> ConduitM Event o m (Maybe c) Source #
A simplified version of tag
where the NameMatcher
result isn't forwarded to the attributes parser.
Since 1.5.0
:: MonadThrow m | |
=> NameMatcher a | Check if this is a correct tag name |
-> ConduitM Event o m b | Handler function to handle the children of the matched tag |
-> ConduitM Event o m (Maybe b) |
A further simplified tag parser, which requires that no attributes exist.
:: MonadThrow m | |
=> NameMatcher a | Check if this is a correct tag name |
-> ConduitM Event o m b | Handler function to handle the children of the matched tag |
-> ConduitM Event o m (Maybe b) |
A further simplified tag parser, which ignores all attributes, if any exist
content :: MonadThrow m => Consumer Event m Text Source #
Grabs the next piece of content. If none if available, returns empty
.
This is simply a wrapper around contentMaybe
.
contentMaybe :: MonadThrow m => Consumer Event m (Maybe Text) Source #
Grabs the next piece of content if available. This function skips over any comments and instructions and concatenates all content until the next start or end tag.
Ignoring tags/trees
:: MonadThrow m | |
=> NameMatcher a | Check if this is a correct tag name |
-> ConduitM Event o m (Maybe ()) |
Deprecated: Please use ignoreEmptyTag
.
:: MonadThrow m | |
=> NameMatcher a | Check if this is a correct tag name |
-> ConduitM Event o m (Maybe ()) |
Ignore an empty tag and all of its attributes.
This does not ignore the tag recursively
(i.e. it assumes there are no child elements).
This function returns Just ()
if the tag matched.
Since 1.5.0
:: MonadThrow m | |
=> NameMatcher a | Check if this is a correct tag name |
-> ConduitM Event o m (Maybe ()) |
Deprecated: Please use ignoreTreeContent
.
:: MonadThrow m | |
=> NameMatcher a | Check if this is a correct tag name |
-> ConduitM Event o m (Maybe ()) |
Ignore a tag, its attributes and its children subtrees recursively.
Both content and text events are ignored.
This function returns Just ()
if the tag matched.
Since 1.5.0
ignoreAnyTreeContent :: MonadThrow m => ConduitM Event o m (Maybe ()) Source #
Like ignoreTreeContent
, but matches any name and also ignores content events.
ignoreAllTreesContent :: MonadThrow m => ConduitM Event o m (Maybe ()) Source #
Deprecated: Please use ignoreAnyTreeContent
.
Streaming events
takeContent :: MonadThrow m => ConduitM Event Event m (Maybe ()) Source #
takeTree :: MonadThrow m => NameMatcher a -> AttrParser b -> ConduitM Event Event m (Maybe ()) Source #
Stream Event
s corresponding to a single element that matches given NameMatcher
and AttrParser
, from the opening- to the closing-tag.
If next Event
isn't an element, nothing is consumed.
If an opening-tag is consumed but no matching closing-tag is found, an XmlException
is thrown.
This function automatically ignores comments, instructions and whitespace.
Returns Just ()
if an element was consumed, Nothing
otherwise.
Since 1.5.0
takeTreeContent :: MonadThrow m => NameMatcher a -> AttrParser b -> ConduitM Event Event m (Maybe ()) Source #
takeAnyTreeContent :: MonadThrow m => ConduitM Event Event m (Maybe ()) Source #
Like takeTreeContent
, without checking for tag name or attributes.
>>>
runResourceT $ parseLBS def "text<a></a>" $$ takeAnyTreeContent =$= consume
Just [ EventContent (ContentText "text") ]
>>>
runResourceT $ parseLBS def "</a><b></b>" $$ takeAnyTreeContent =$= consume
Just [ ]
>>>
runResourceT $ parseLBS def "<b><c></c></b></a>text" $$ takeAnyTreeContent =$= consume
Just [ EventBeginElement "b" [], EventBeginElement "c" [], EventEndElement "c", EventEndElement "b" ]
Since 1.5.0
takeAllTreesContent :: MonadThrow m => ConduitM Event Event m (Maybe ()) Source #
Deprecated: Please use takeAnyTreeContent
.
Tag name matching
newtype NameMatcher a Source #
A NameMatcher
describes which names a tag parser is allowed to match.
Since 1.5.0
NameMatcher | |
|
Functor NameMatcher Source # | |
Applicative NameMatcher Source # | |
Alternative NameMatcher Source # |
|
(~) * a Name => IsString (NameMatcher a) Source # | Match a single |
matching :: (Name -> Bool) -> NameMatcher Name Source #
matching f
matches name
iff f name
is true. Returns the matched Name
.
Since 1.5.0
Attribute parsing
data AttrParser a Source #
A monad for parsing attributes. By default, it requires you to deal with
all attributes present on an element, and will throw an exception if there
are unhandled attributes. Use the requireAttr
, attr
et al
functions for handling an attribute, and ignoreAttrs
if you would like to
skip the rest of the attributes on an element.
Alternative
instance behaves like First
monoid: it chooses first
parser which doesn't fail.
requireAttr :: Name -> AttrParser Text Source #
optionalAttr :: Name -> AttrParser (Maybe Text) Source #
Deprecated: Please use attr
.
requireAttrRaw :: String -> ((Name, [Content]) -> Maybe b) -> AttrParser b Source #
optionalAttrRaw :: ((Name, [Content]) -> Maybe b) -> AttrParser (Maybe b) Source #
ignoreAttrs :: AttrParser () Source #
Skip the remaining attributes on an element. Since this will clear the
list of attributes, you must call this after any calls to requireAttr
,
optionalAttr
, etc.
Combinators
many :: Monad m => ConduitM Event o m (Maybe a) -> ConduitM Event o m [a] Source #
Keep parsing elements as long as the parser returns Just
.
many_ :: MonadThrow m => ConduitM Event o m (Maybe a) -> ConduitM Event o m () Source #
Like many
but discards the results without building an intermediate list.
Since 1.5.0
manyIgnore :: Monad m => ConduitM Event o m (Maybe a) -> ConduitM Event o m (Maybe b) -> ConduitM Event o m [a] Source #
many' :: MonadThrow m => ConduitM Event o m (Maybe a) -> ConduitM Event o m [a] Source #
Like many
, but any tags and content the consumer doesn't match on
are silently ignored.
:: MonadThrow m | |
=> String | Error message |
-> m (Maybe a) | Optional parser to be forced |
-> m a |
Streaming combinators
manyYield' :: MonadThrow m => ConduitM Event b m (Maybe b) -> Conduit Event m b Source #
Like many'
, but uses yield
so the result list can be streamed
to downstream conduits without waiting for manyYield'
to finish
:: MonadThrow m | |
=> ConduitM Event b m (Maybe b) | Consuming parser that generates the result stream |
-> ConduitM Event b m (Maybe ()) | Ignore parser that consumes elements to be ignored |
-> Conduit Event m b |
Like manyIgnore
, but uses yield
so the result list can be streamed
to downstream conduits without waiting for manyIgnoreYield
to finish
Exceptions
data XmlException Source #
Other types
data PositionRange :: * #