Redo FromJSON for Opt so that optional values can be omitted.

It would have been cleaner to make all of these values Maybes,
so the JSON could be derived automatically. But this method preserves
the existing API.

1 files changed, 86 insertions, 3 deletions

diff --git a/src/Text/Pandoc/App/Opt.hs b/src/Text/Pandoc/App/Opt.hs
index 5d15560d8..57951347d 100644
--- a/src/Text/Pandoc/App/Opt.hs
+++ b/src/Text/Pandoc/App/Opt.hs
@@ -54,7 +54,8 @@ import qualified Data.Text as T
 import qualified Data.Map as M
 import qualified Data.ByteString.Char8 as B8
 import Text.Pandoc.Definition (Meta(..), MetaValue(..))
-import Data.Aeson (defaultOptions, Options(..), Result(..), fromJSON, camelTo2)
+import Data.Aeson (defaultOptions, Options(..), Result(..), camelTo2,
+                   genericToJSON, fromJSON)
 import Data.Aeson.TH (deriveJSON)
 import Control.Applicative ((<|>))
 import Data.Yaml
@@ -156,8 +157,90 @@ data Opt = Opt
     , optSandbox               :: Bool
     } deriving (Generic, Show)
 
-$(deriveJSON
-   defaultOptions{ fieldLabelModifier = camelTo2 '-' . drop 3 } ''Opt)
+instance FromJSON Opt where
+   parseJSON = withObject "Opt" $ \o ->
+     Opt
+       <$> o .:? "tab-stop" .!= optTabStop defaultOpts
+       <*> o .:? "preserve-tabs" .!= optPreserveTabs defaultOpts
+       <*> o .:? "standalone" .!= optStandalone defaultOpts
+       <*> o .:? "from"
+       <*> o .:? "to"
+       <*> o .:? "table-of-contents" .!= optTableOfContents defaultOpts
+       <*> o .:? "shift-heading-level-by" .!= optShiftHeadingLevelBy defaultOpts
+       <*> o .:? "template"
+       <*> o .:? "variables" .!= optVariables defaultOpts
+       <*> o .:? "metadata" .!= optMetadata defaultOpts
+       <*> o .:? "metadata-files" .!= optMetadataFiles defaultOpts
+       <*> o .:? "output-file"
+       <*> o .:? "input-files"
+       <*> o .:? "number-sections" .!= optNumberSections defaultOpts
+       <*> o .:? "number-offset" .!= optNumberOffset defaultOpts
+       <*> o .:? "section-divs" .!= optSectionDivs defaultOpts
+       <*> o .:? "incremental" .!= optIncremental defaultOpts
+       <*> o .:? "self-contained" .!= optSelfContained defaultOpts
+       <*> o .:? "embed-resources" .!= optEmbedResources defaultOpts
+       <*> o .:? "html-q-tags" .!= optHtmlQTags defaultOpts
+       <*> o .:? "highlight-style"
+       <*> o .:? "syntax-definitions" .!= optSyntaxDefinitions defaultOpts
+       <*> o .:? "top-level-division" .!= optTopLevelDivision defaultOpts
+       <*> o .:? "html-math-method" .!= optHTMLMathMethod defaultOpts
+       <*> o .:? "abbreviations"
+       <*> o .:? "reference-doc"
+       <*> o .:? "epub-subdirectory" .!= optEpubSubdirectory defaultOpts
+       <*> o .:? "epub-metadata"
+       <*> o .:? "epub-fonts" .!= optEpubFonts defaultOpts
+       <*> o .:? "epub-chapter-level" .!= optEpubChapterLevel defaultOpts
+       <*> o .:? "epub-cover-image"
+       <*> o .:? "toc-depth" .!= optTOCDepth defaultOpts
+       <*> o .:? "dump-args" .!= optDumpArgs defaultOpts
+       <*> o .:? "ignore-args" .!= optIgnoreArgs defaultOpts
+       <*> o .:? "verbosity" .!= optVerbosity defaultOpts
+       <*> o .:? "trace" .!= optTrace defaultOpts
+       <*> o .:? "log-file"
+       <*> o .:? "fail-if-warnings" .!= optFailIfWarnings defaultOpts
+       <*> o .:? "reference-links" .!= optReferenceLinks defaultOpts
+       <*> o .:? "reference-location" .!= optReferenceLocation defaultOpts
+       <*> o .:? "dpi" .!= optDpi defaultOpts
+       <*> o .:? "wrap" .!= optWrap defaultOpts
+       <*> o .:? "columns" .!= optColumns defaultOpts
+       <*> o .:? "filters" .!= optFilters defaultOpts
+       <*> o .:? "email-obfuscation" .!= optEmailObfuscation defaultOpts
+       <*> o .:? "identifier-prefix" .!= optIdentifierPrefix defaultOpts
+       <*> o .:? "strip-empty-paragraphs" .!= optStripEmptyParagraphs defaultOpts
+       <*> o .:? "indented-code-classes" .!= optIndentedCodeClasses defaultOpts
+       <*> o .:? "data-dir"
+       <*> o .:? "cite-method" .!= optCiteMethod defaultOpts
+       <*> o .:? "listings" .!= optListings defaultOpts
+       <*> o .:? "pdf-engine"
+       <*> o .:? "pdf-engine-opts" .!= optPdfEngineOpts defaultOpts
+       <*> o .:? "slide-level"
+       <*> o .:? "setext-headers" .!= optSetextHeaders defaultOpts
+       <*> o .:? "ascii" .!= optAscii defaultOpts
+       <*> o .:? "default-image-extension" .!= optDefaultImageExtension defaultOpts
+       <*> o .:? "extract-media"
+       <*> o .:? "track-changes" .!= optTrackChanges defaultOpts
+       <*> o .:? "file-scope" .!= optFileScope defaultOpts
+       <*> o .:? "title-prefix" .!= optTitlePrefix defaultOpts
+       <*> o .:? "css" .!= optCss defaultOpts
+       <*> o .:? "ipynb-output" .!= optIpynbOutput defaultOpts
+       <*> o .:? "include-before-body" .!= optIncludeBeforeBody defaultOpts
+       <*> o .:? "include-after-body" .!= optIncludeAfterBody defaultOpts
+       <*> o .:? "include-in-header" .!= optIncludeInHeader defaultOpts
+       <*> o .:? "resource-path" .!= optResourcePath defaultOpts
+       <*> o .:? "request-headers" .!= optRequestHeaders defaultOpts
+       <*> o .:? "no-check-certificate" .!= optNoCheckCertificate defaultOpts
+       <*> o .:? "eol" .!= optEol defaultOpts
+       <*> o .:? "strip-comments" .!= optStripComments defaultOpts
+       <*> o .:? "csl"
+       <*> o .:? "bibliography" .!= optBibliography defaultOpts
+       <*> o .:? "citation-abbreviations"
+       <*> o .:? "sandbox" .!= optSandbox defaultOpts
+
+instance ToJSON Opt where
+ toJSON = genericToJSON defaultOptions{
+                                 fieldLabelModifier = camelTo2 '-' . drop 3,
+                                 omitNothingFields = True }
+
 
 instance FromJSON (Opt -> Opt) where
   parseJSON (Object m) =