This module provides functions to parse an XML document to a tree structure, either strictly or lazily, as well as a lazy SAX-style interface.

The GenericXMLString type class allows you to use any string type. Three string types are provided for here: String, ByteString and Text.

Error handling in strict parses is very straight forward - just check the Either return value. Lazy parses are not so simple. Here are two working examples that illustrate the ways to handle errors. Here they are:

Way no. 1

 import Text.XML.Expat.Tree
 import qualified Data.ByteString.Lazy as L
 import Data.ByteString.Internal (c2w)
 import Control.Exception.Extensible as E
 
 -- This is the recommended way to handle errors in lazy parses
 main = do
     let (tree, mError) = parseTree Nothing (L.pack $ map c2w $ "<top><banana></apple></top>")
     print (tree :: UNode String)
     -- Note: We check the error _after_ we have finished our processing on the tree.
     case mError of
         Just err -> putStrLn $ "It failed : "++show err
         Nothing -> putStrLn "Success!"

Way no. 2

 ...
 import Control.Exception.Extensible as E
 
 -- This is not the recommended way to handle errors.
 main = do
     do
         let tree = parseTreeThrowing Nothing (L.pack $ map c2w $ "<top><banana></apple></top>")
         print (tree :: UNode String)
         -- Because of lazy evaluation, you should not process the tree outside the 'do' block,
         -- or exceptions could be thrown that won't get caught.
     `E.catch` (\exc ->
         case E.fromException exc of
             Just (XMLParseException err) -> putStrLn $ "It failed : "++show err
             Nothing -> E.throwIO exc)