xml-hamlet does not honour namespaces.

[fisx]

I want to render a piece of xml with namespaces, but the xmlns keyword is interpreted as an ordinary attribute:

{-# LANGUAGE OverloadedStrings #-}
{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}

import Text.Hamlet.XML as Hamlet
import Text.XML
import Text.XML.Cursor

test :: IO ()
test = parseSomething renderSomething

parseSomething :: Element -> IO ()
parseSomething el = do
  let cur = fromNode $ NodeElement el
      tick = cur $| element "{some:namespace}tick"
      tack = cur $/ element "{some:namespace}tack"

  print (length tick, length tack, cur)

renderSomething :: Element
renderSomething = el
  where
    [NodeElement el] = [Hamlet.xml|
      <tick xmlns="some:namespace">
          <tack>
      |]

expected behavior: output should be (1, 1, ..), and the xmlns keyword should not be in the attribute list.

observed behavior: output is (0, 0, ..), and the xmlns keyword is listed as an ordinary attribute.

[snoyberg]

I have no intention of modifying the xml-hamlet parser to have special support for xmlns right now. If you're interested in having this behavior, you'd need to send a PR yourself.

[fisx]

I'd love to fix this, but I don't think I'll find the time for this before xml comes out of fashion.

Oh, I just thought of something: what will go wrong if I replace Text.Hamlet.XMLParse.parseDoc with the xml-conduit parser?

workaround

-- | https://github.com/snoyberg/xml/issues/137
repairNamespaces :: HasCallStack => [Node] -> [Node]
repairNamespaces = fmap $ \case
  NodeElement el -> NodeElement $ repairNamespacesEl el
  other -> other

-- | https://github.com/snoyberg/xml/issues/137
repairNamespacesEl :: HasCallStack => Element -> Element
repairNamespacesEl el = unwrap . parseText def . renderText def . mkDocument $ el
  where
    unwrap (Right (Document _ el' _)) = el'
    unwrap (Left msg) = error $ show msg