Improve parsing of --defaults.

- Add FromYAML instances to Opt and to all subsidiary types.
- Remove the use of HsYAML-aeson, which doesn't give good
  position information on errors.
- Rename some fields in Opt to better match cli options or
  reflect what the ycontain [API change]:

  + optMetadataFile -> optMetadataFiles
  + optPDFEngineArgs -> optPDFEngineOpts
  + optWrapText -> optWrap
- Add IpynbOutput enumerated type to Text.Pandoc.App.Opts.
  Use this instead fo a string for optIpynbOutput.
- Add FromYAML instance for Filter in Text.Pandoc.Filters.

With these changes parsing of defaults files should be
complete and should give decent error messages.

Now (unlike before) we get an error if an unknown field
is used.

1 files changed, 97 insertions, 1 deletions

diff --git a/src/Text/Pandoc/Options.hs b/src/Text/Pandoc/Options.hs
index 5dc94b2ad..5ff4504df 100644
--- a/src/Text/Pandoc/Options.hs
+++ b/src/Text/Pandoc/Options.hs
@@ -3,6 +3,7 @@
 {-# LANGUAGE DeriveGeneric      #-}
 {-# LANGUAGE NoImplicitPrelude  #-}
 {-# LANGUAGE TemplateHaskell    #-}
+{-# LANGUAGE OverloadedStrings  #-}
 {- |
    Module      : Text.Pandoc.Options
    Copyright   : Copyright (C) 2012-2019 John MacFarlane
@@ -29,12 +30,15 @@ module Text.Pandoc.Options ( module Text.Pandoc.Extensions
                            , ReferenceLocation (..)
                            , def
                            , isEnabled
+                           , defaultMathJaxURL
+                           , defaultKaTeXURL
                            ) where
 import Prelude
+import Control.Applicative ((<|>))
 import Data.Char (toLower)
 import Data.Data (Data)
 import Data.Default
-import Data.Text (Text)
+import Data.Text (Text, unpack)
 import Text.DocTemplates (Context(..))
 import qualified Data.Set as Set
 import Data.Typeable (Typeable)
@@ -46,6 +50,7 @@ import Text.Pandoc.Shared (camelCaseToHyphenated)
 import Text.DocTemplates (Template)
 import Data.Aeson.TH (deriveJSON, defaultOptions, Options(..),
                       SumEncoding(..))
+import Data.YAML
 
 class HasSyntaxExtensions a where
   getExtensions :: a -> Extensions
@@ -101,17 +106,58 @@ data HTMLMathMethod = PlainMath
                     | KaTeX String                -- url of KaTeX files
                     deriving (Show, Read, Eq, Data, Typeable, Generic)
 
+instance FromYAML HTMLMathMethod where
+   parseYAML node =
+     (withMap "HTMLMathMethod" $ \m -> do
+        method <- m .: "method"
+        mburl <- m .:? "url"
+        case unpack method of
+          "plain" -> return PlainMath
+          "webtex" -> return $ WebTeX $ maybe "" unpack mburl
+          "gladtex" -> return GladTeX
+          "mathml" -> return MathML
+          "mathjax" -> return $ MathJax $
+                         maybe defaultMathJaxURL unpack mburl
+          "katex" -> return $ KaTeX $
+                         maybe defaultKaTeXURL unpack mburl
+          _ -> fail $ "Unknown HTML math method " ++ show method) node
+       <|> (withStr "HTMLMathMethod" $ \method ->
+             case unpack method of
+               "plain" -> return PlainMath
+               "webtex" -> return $ WebTeX ""
+               "gladtex" -> return GladTeX
+               "mathml" -> return MathML
+               "mathjax" -> return $ MathJax defaultMathJaxURL
+               "katex" -> return $ KaTeX defaultKaTeXURL
+               _  -> fail $ "Unknown HTML math method " ++ show method) node
+
 data CiteMethod = Citeproc                        -- use citeproc to render them
                   | Natbib                        -- output natbib cite commands
                   | Biblatex                      -- output biblatex cite commands
                 deriving (Show, Read, Eq, Data, Typeable, Generic)
 
+instance FromYAML CiteMethod where
+  parseYAML = withStr "Citeproc" $ \t ->
+    case t of
+      "citeproc" -> return Citeproc
+      "natbib"   -> return Natbib
+      "biblatex" -> return Biblatex
+      _          -> fail $ "Unknown citation method " ++ show t
+
 -- | Methods for obfuscating email addresses in HTML.
 data ObfuscationMethod = NoObfuscation
                        | ReferenceObfuscation
                        | JavascriptObfuscation
                        deriving (Show, Read, Eq, Data, Typeable, Generic)
 
+instance FromYAML ObfuscationMethod where
+  parseYAML = withStr "Citeproc" $ \t ->
+    case t of
+      "none"       -> return NoObfuscation
+      "references" -> return ReferenceObfuscation
+      "javascript" -> return JavascriptObfuscation
+      _            -> fail $ "Unknown obfuscation method " ++ show t
+
 -- | Varieties of HTML slide shows.
 data HTMLSlideVariant = S5Slides
                       | SlidySlides
@@ -127,12 +173,29 @@ data TrackChanges = AcceptChanges
                   | AllChanges
                   deriving (Show, Read, Eq, Data, Typeable, Generic)
 
+instance FromYAML TrackChanges where
+  parseYAML = withStr "TrackChanges" $ \t ->
+    case t of
+      "accept"     -> return AcceptChanges
+      "reject"     -> return RejectChanges
+      "all"        -> return AllChanges
+      _            -> fail $ "Unknown track changes method " ++ show t
+
 -- | Options for wrapping text in the output.
 data WrapOption = WrapAuto        -- ^ Automatically wrap to width
                 | WrapNone        -- ^ No non-semantic newlines
                 | WrapPreserve    -- ^ Preserve wrapping of input source
                 deriving (Show, Read, Eq, Data, Typeable, Generic)
 
+instance FromYAML WrapOption where
+  parseYAML = withStr "WrapOption" $ \t ->
+    case t of
+      "auto"     -> return WrapAuto
+      "none"     -> return WrapNone
+      "preserve" -> return WrapPreserve
+      _          -> fail $ "Unknown wrap method " ++ show t
+
+
 -- | Options defining the type of top-level headers.
 data TopLevelDivision = TopLevelPart      -- ^ Top-level headers become parts
                       | TopLevelChapter   -- ^ Top-level headers become chapters
@@ -141,12 +204,31 @@ data TopLevelDivision = TopLevelPart      -- ^ Top-level headers become parts
                                           --   heuristics
                       deriving (Show, Read, Eq, Data, Typeable, Generic)
 
+instance FromYAML TopLevelDivision where
+  parseYAML = withStr "TopLevelDivision" $ \t ->
+    case t of
+      "part"     -> return TopLevelPart
+      "chapter"  -> return TopLevelChapter
+      "section"  -> return TopLevelSection
+      "default"  -> return TopLevelDefault
+      _          -> fail $ "Unknown top level division " ++ show t
+
+
 -- | Locations for footnotes and references in markdown output
 data ReferenceLocation = EndOfBlock    -- ^ End of block
                        | EndOfSection  -- ^ prior to next section header (or end of document)
                        | EndOfDocument -- ^ at end of document
                        deriving (Show, Read, Eq, Data, Typeable, Generic)
 
+instance FromYAML ReferenceLocation where
+  parseYAML = withStr "ReferenceLocation" $ \t ->
+    case t of
+      "block"    -> return EndOfBlock
+      "section"  -> return EndOfSection
+      "document" -> return EndOfDocument
+      _          -> fail $ "Unknown reference location " ++ show t
+
+
 -- | Options for writers
 data WriterOptions = WriterOptions
   { writerTemplate          :: Maybe Template -- ^ Template to use
@@ -227,16 +309,25 @@ instance HasSyntaxExtensions WriterOptions where
 isEnabled :: HasSyntaxExtensions a => Extension -> a -> Bool
 isEnabled ext opts = ext `extensionEnabled` getExtensions opts
 
+defaultMathJaxURL :: String
+defaultMathJaxURL = "https://cdn.jsdelivr.net/npm/mathjax@3/es5/"
+
+defaultKaTeXURL :: String
+defaultKaTeXURL = "https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.9.0/"
+
 $(deriveJSON defaultOptions ''ReaderOptions)
+
 $(deriveJSON defaultOptions{
    constructorTagModifier = map toLower,
    sumEncoding = TaggedObject{
                     tagFieldName = "method",
                     contentsFieldName = "url" }
                            } ''HTMLMathMethod)
+
 $(deriveJSON defaultOptions{ constructorTagModifier =
                                camelCaseToHyphenated
                            } ''CiteMethod)
+
 $(deriveJSON defaultOptions{ constructorTagModifier =
                             \t -> case t of
                                     "NoObfuscation"         -> "none"
@@ -244,16 +335,21 @@ $(deriveJSON defaultOptions{ constructorTagModifier =
                                     "JavascriptObfuscation" -> "javascript"
                                     _                       -> "none"
                            } ''ObfuscationMethod)
+
 $(deriveJSON defaultOptions ''HTMLSlideVariant)
+
 $(deriveJSON defaultOptions{ constructorTagModifier =
                                camelCaseToHyphenated
                            } ''TrackChanges)
+
 $(deriveJSON defaultOptions{ constructorTagModifier =
                                camelCaseToHyphenated
                            } ''WrapOption)
+
 $(deriveJSON defaultOptions{ constructorTagModifier =
                                camelCaseToHyphenated . drop 8
                            } ''TopLevelDivision)
+
 $(deriveJSON defaultOptions{ constructorTagModifier =
                                camelCaseToHyphenated
                            } ''ReferenceLocation)