Change JSON encodings of some types.

- For LineEnding use lowercase constructors, e.g. `crlf`, `native`.
  This was the original intent, but there was a bug in the
  implementation.
- For HTMLSlideVariant use lowercase constructors.
- For ReaderOptions use e.g. `default-image-extension`
  instead of `readerDefaultImageExtension` for field names.
- For Extension, use e.g. `tex_math_dollars` instead of
  `Ext_tex_math_dollars` as constructor.
- For Extensions, use an array of Extensions, instead of
  an object wrapping the tag `Extensions` and an integer.
  (The representation is not supposed to be part of the
  public API.)
- For Opt, use field names like `tab-stop` instead of `optTabStop`.

3 files changed, 56 insertions, 44 deletions

diff --git a/src/Text/Pandoc/App/Opt.hs b/src/Text/Pandoc/App/Opt.hs
index 93953d53f..c5fac7951 100644
--- a/src/Text/Pandoc/App/Opt.hs
+++ b/src/Text/Pandoc/App/Opt.hs
@@ -29,7 +29,7 @@ import Control.Monad.Except (MonadIO, liftIO, throwError, (>=>), foldM)
 import Control.Monad.State.Strict (StateT, modify, gets)
 import System.FilePath ( addExtension, (</>), takeExtension, takeDirectory )
 import System.Directory ( canonicalizePath )
-import Data.Char (isLower, toLower)
+import Data.Char (toLower)
 import Data.Maybe (fromMaybe)
 import GHC.Generics hiding (Meta)
 import Text.Pandoc.Filter (Filter (..))
@@ -43,8 +43,7 @@ import Text.Pandoc.Options (TopLevelDivision (TopLevelDefault),
 import Text.Pandoc.Class (readFileStrict, fileExists, setVerbosity, report,
                           PandocMonad(lookupEnv), getUserDataDir)
 import Text.Pandoc.Error (PandocError (PandocParseError, PandocSomeError))
-import Text.Pandoc.Shared (camelCaseStrToHyphenated, defaultUserDataDir,
-                           findM, ordNub)
+import Text.Pandoc.Shared (defaultUserDataDir, findM, ordNub)
 import qualified Text.Pandoc.Parsing as P
 import Text.Pandoc.Readers.Metadata (yamlMap)
 import Text.Pandoc.Class.PandocPure
@@ -54,7 +53,7 @@ import Data.Default (def)
 import qualified Data.Text as T
 import qualified Data.Map as M
 import Text.Pandoc.Definition (Meta(..), MetaValue(..))
-import Data.Aeson (defaultOptions, Options(..), Result(..), fromJSON)
+import Data.Aeson (defaultOptions, Options(..), Result(..), fromJSON, camelTo2)
 import Data.Aeson.TH (deriveJSON)
 import Control.Applicative ((<|>))
 import Data.Yaml
@@ -62,6 +61,11 @@ import Data.Yaml
 -- | The type of line-endings to be used when writing plain-text.
 data LineEnding = LF | CRLF | Native deriving (Show, Generic)
 
+-- see https://github.com/jgm/pandoc/pull/4083
+-- using generic deriving caused long compilation times
+$(deriveJSON
+   defaultOptions{ constructorTagModifier = map toLower } ''LineEnding)
+
 -- | How to handle output blocks in ipynb.
 data IpynbOutput =
     IpynbOutputAll
@@ -69,6 +73,9 @@ data IpynbOutput =
   | IpynbOutputBest
   deriving (Show, Generic)
 
+$(deriveJSON
+   defaultOptions{ fieldLabelModifier = map toLower . drop 11 } ''IpynbOutput)
+
 -- | Data structure for command line options.
 data Opt = Opt
     { optTabStop               :: Int     -- ^ Number of spaces per tab
@@ -147,6 +154,9 @@ data Opt = Opt
     , optSandbox               :: Bool
     } deriving (Generic, Show)
 
+$(deriveJSON
+   defaultOptions{ fieldLabelModifier = camelTo2 '-' . drop 3 } ''Opt)
+
 instance FromJSON (Opt -> Opt) where
   parseJSON (Object m) =
     case fromJSON (Object m) of
@@ -714,14 +724,3 @@ cyclic :: Ord a => [[a]] -> Bool
 cyclic = any hasDuplicate
   where
     hasDuplicate xs = length (ordNub xs) /= length xs
-
--- see https://github.com/jgm/pandoc/pull/4083
--- using generic deriving caused long compilation times
-$(deriveJSON
-   defaultOptions{ fieldLabelModifier = drop 11 . map toLower } ''IpynbOutput)
-$(deriveJSON
-   defaultOptions{ fieldLabelModifier = map toLower } ''LineEnding)
-$(deriveJSON
-   defaultOptions{ fieldLabelModifier =
-                      camelCaseStrToHyphenated . dropWhile isLower
-                 } ''Opt)
diff --git a/src/Text/Pandoc/Extensions.hs b/src/Text/Pandoc/Extensions.hs
index 831190e33..ce6a95458 100644
--- a/src/Text/Pandoc/Extensions.hs
+++ b/src/Text/Pandoc/Extensions.hs
@@ -40,31 +40,8 @@ import Data.Typeable (Typeable)
 import GHC.Generics (Generic)
 import Safe (readMay)
 import Text.Parsec
-import Data.Aeson.TH (deriveJSON, defaultOptions)
-
-newtype Extensions = Extensions Integer
-  deriving (Show, Read, Eq, Ord, Data, Typeable, Generic)
-
-instance Semigroup Extensions where
-  (Extensions a) <> (Extensions b) = Extensions (a .|. b)
-instance Monoid Extensions where
-  mempty = Extensions 0
-  mappend = (<>)
-
-extensionsFromList :: [Extension] -> Extensions
-extensionsFromList = foldr enableExtension emptyExtensions
-
-emptyExtensions :: Extensions
-emptyExtensions = Extensions 0
-
-extensionEnabled :: Extension -> Extensions -> Bool
-extensionEnabled x (Extensions exts) = testBit exts (fromEnum x)
-
-enableExtension :: Extension -> Extensions -> Extensions
-enableExtension x (Extensions exts) = Extensions (setBit exts (fromEnum x))
-
-disableExtension :: Extension -> Extensions -> Extensions
-disableExtension x (Extensions exts) = Extensions (clearBit exts (fromEnum x))
+import Data.Aeson.TH (deriveJSON)
+import Data.Aeson
 
 -- | Individually selectable syntax extensions.
 data Extension =
@@ -162,6 +139,40 @@ data Extension =
     | Ext_yaml_metadata_block -- ^ YAML metadata block
     deriving (Show, Read, Enum, Eq, Ord, Bounded, Data, Typeable, Generic)
 
+$(deriveJSON defaultOptions{ constructorTagModifier = drop 4 } ''Extension)
+
+newtype Extensions = Extensions Integer
+  deriving (Show, Read, Eq, Ord, Data, Typeable, Generic)
+
+instance Semigroup Extensions where
+  (Extensions a) <> (Extensions b) = Extensions (a .|. b)
+instance Monoid Extensions where
+  mempty = Extensions 0
+  mappend = (<>)
+
+instance FromJSON Extensions where
+  parseJSON =
+    return . foldr enableExtension emptyExtensions . fromJSON
+
+instance ToJSON Extensions where
+  toJSON exts = toJSON $
+    [ext | ext <- [minBound..maxBound], extensionEnabled ext exts]
+
+extensionsFromList :: [Extension] -> Extensions
+extensionsFromList = foldr enableExtension emptyExtensions
+
+emptyExtensions :: Extensions
+emptyExtensions = Extensions 0
+
+extensionEnabled :: Extension -> Extensions -> Bool
+extensionEnabled x (Extensions exts) = testBit exts (fromEnum x)
+
+enableExtension :: Extension -> Extensions -> Extensions
+enableExtension x (Extensions exts) = Extensions (setBit exts (fromEnum x))
+
+disableExtension :: Extension -> Extensions -> Extensions
+disableExtension x (Extensions exts) = Extensions (clearBit exts (fromEnum x))
+
 -- | Extensions to be used with pandoc-flavored markdown.
 pandocExtensions :: Extensions
 pandocExtensions = extensionsFromList
@@ -618,5 +629,3 @@ parseFormatSpec = parse formatSpec ""
                         '+' -> (ext : extsToEnable, extsToDisable)
                         _   -> (extsToEnable, ext : extsToDisable)
 
-$(deriveJSON defaultOptions ''Extension)
-$(deriveJSON defaultOptions ''Extensions)
diff --git a/src/Text/Pandoc/Options.hs b/src/Text/Pandoc/Options.hs
index ba18377c2..6a3028b14 100644
--- a/src/Text/Pandoc/Options.hs
+++ b/src/Text/Pandoc/Options.hs
@@ -37,6 +37,7 @@ import Control.Applicative ((<|>))
 import Data.Maybe (fromMaybe)
 import Data.Data (Data)
 import Data.Default
+import Data.Char (toLower)
 import Data.Text (Text)
 import qualified Data.Set as Set
 import Data.Typeable (Typeable)
@@ -371,6 +372,9 @@ defaultKaTeXURL :: Text
 defaultKaTeXURL = "https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.11.1/"
 
 -- Update documentation in doc/filters.md if this is changed.
-$(deriveJSON defaultOptions ''ReaderOptions)
+$(deriveJSON defaultOptions{ fieldLabelModifier =
+                               camelTo2 '-' . drop 6 }
+                            ''ReaderOptions)
 
-$(deriveJSON defaultOptions ''HTMLSlideVariant)
+$(deriveJSON defaultOptions{ constructorTagModifier = map toLower }
+  ''HTMLSlideVariant)