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{-|
Module : QuoteStr
Description : Quasiquoter for multi-line string literals
Copyright : (c) Eric Mertens, 2023
License : ISC
Maintainer : emertens@gmail.com
This module makes it easy to write inline TOML for
test cases without worrying about escaping newlines
or quotation marks.
-}
module QuoteStr (quoteStr) where
import Language.Haskell.TH (Exp(LitE), ExpQ, Lit(StringL))
import Language.Haskell.TH.Quote ( QuasiQuoter(..) )
import Data.List ( stripPrefix )
quoteStr :: QuasiQuoter
quoteStr = QuasiQuoter {
quoteDec = \_ -> fail "quoteStr doesn't support declarations",
quotePat = \_ -> fail "quoteStr doesn't support patterns",
quoteType = \_ -> fail "quoteStr doesn't support types",
quoteExp = processString
}
processString :: String -> ExpQ
processString ('\n':xs) =
let ws = takeWhile (' '==) xs
cleanup "" = pure ""
cleanup x = case stripPrefix ws x of
Nothing -> fail "bad prefix"
Just x' -> pure x'
in LitE . StringL . unlines <$> traverse cleanup (lines xs)
processString _ = fail "malformed string literal"
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