Comply with recent grammar changes

[sjakobi]

• Allow quoted labels to be empty dhall-lang#980
• Remove the ability to quote paths in URLs dhall-lang#1005

---

TODO:

• Update prettyprinter
• Does the marshalling code need any updates to handle empty labels?

[sjakobi]

[ ] Update prettyprinter

I haven't found anything to change. Here's the URL prettyprinter:

dhall-haskell/dhall/src/Dhall/Syntax.hs

Lines 794 to 823 in b9cbc63

	instance Pretty URL where
	pretty (URL {..}) =
	schemeDoc
	<> "://"
	<> Pretty.pretty authority
	<> pathDoc
	<> queryDoc
	<> foldMap prettyHeaders headers
	where
	prettyHeaders h = " using " <> Pretty.pretty h
	File {..} = path
	Directory {..} = directory
	pathDoc =
	foldMap prettyURIComponent (reverse components)
	<> prettyURIComponent file
	schemeDoc = case scheme of
	HTTP -> "http"
	HTTPS -> "https"
	queryDoc = case query of
	Nothing -> ""
	Just q -> "?" <> Pretty.pretty q
	prettyURIComponent :: Text -> Doc ann
	prettyURIComponent text =
	Pretty.pretty $ URI.normalizeCase $ URI.normalizeEscape $ "/" <> Data.Text.unpack text

[sjakobi]

I believe we'll benefit from the empty labels change in our QuickCheck tests where we previously produced a lot of invalid expressions which contained empty labels.

I'm still wondering whether the same change won't cause a bug in some marshalling/conversion code, but I assume we'll find out when people start using empty labels.