Ipynb reader/writer: better handling of cell metadata.

We now handle even complex cell metadata in the Div's attributes.
Simple metadata fields are rendered as a plain string, and complex ones
as JSON.

src/Text/Pandoc/Readers/Ipynb.hs

@@ -18,6 +18,7 @@ Ipynb (Jupyter notebook JSON format) reader for pandoc.
 module Text.Pandoc.Readers.Ipynb ( readIpynb )
 where
 import Prelude
+import Data.Char (isDigit)
 import Data.List (isPrefixOf)
 import Data.Maybe (fromMaybe)
 import Data.Digest.Pure.SHA (sha1, showDigest)
@@ -39,6 +40,7 @@ import qualified Data.ByteString.Lazy as BL
 import Data.Aeson as Aeson
 import Control.Monad.Except (throwError)
 import Text.Pandoc.Readers.Markdown (readMarkdown)
+import qualified Text.Pandoc.UTF8 as UTF8
 
 readIpynb :: PandocMonad m => ReaderOptions -> Text -> m Pandoc
 readIpynb opts t = do
@@ -217,10 +219,11 @@ jsonMetaToMeta = M.mapKeys T.unpack . M.map valueToMetaValue
     valueToMetaValue Aeson.Null = MetaString ""
 
 jsonMetaToPairs :: JSONMeta -> [(String, String)]
-jsonMetaToPairs = M.toList . M.mapMaybe
-     (\case
-        MetaString s -> Just s
-        MetaBool True -> Just "true"
-        MetaBool False -> Just "false"
-        -- for now we skip complex cell metadata:
-        _ -> Nothing) . jsonMetaToMeta
+jsonMetaToPairs = M.toList . M.mapKeys T.unpack . M.map
+  (\case
+      String t
+        | not (T.all isDigit t)
+        , t /= "true"
+        , t /= "false"
+                 -> T.unpack t
+      x          -> UTF8.toStringLazy $ Aeson.encode x)

src/Text/Pandoc/Writers/Ipynb.hs

@@ -213,10 +213,9 @@ extractData bs = do
 
 pairsToJSONMeta :: [(String, String)] -> JSONMeta
 pairsToJSONMeta kvs =
-  M.fromList [(T.pack k, case v of
-                           "true"  -> Bool True
-                           "false" -> Bool False
-                           _       -> case safeRead v of
-                                        Just n -> Number n
-                                        _      -> String (T.pack v))
-             | (k,v) <- kvs , k /= "execution_count" ]
+  M.fromList [(T.pack k, case Aeson.decode (UTF8.fromStringLazy v) of
+                           Just val -> val
+                           Nothing  -> String (T.pack v))
+             | (k,v) <- kvs
+             , k /= "execution_count"
+             ]

test/ipynb/simple.in.native

@@ -8,6 +8,6 @@ Pandoc (Meta {unMeta = fromList [("jupyter",MetaMap (fromList [("nbformat",MetaI
  [Header 2 ("pyout",[],[]) [Str "Pyout"]]
 ,Div ("",["cell","code"],[])
  [CodeBlock ("",["python"],[]) "from IPython.display import HTML\nHTML(\"\"\"\n<script>\nconsole.log(\"hello\");\n</script>\n<b>HTML</b>\n\"\"\")"]
-,Div ("",["cell","markdown"],[])
+,Div ("",["cell","markdown"],[("tags","[\"foo\",\"bar\"]")])
  [Header 2 ("image",[],[]) [Str "Image"]
  ,Para [Str "This",Space,Str "image",Space,Image ("",[],[]) [Str "the",Space,Str "moon"] ("lalune.jpg",""),Space,Str "will",Space,Str "be",Space,Str "included",Space,Str "as",Space,Str "a",Space,Str "cell",SoftBreak,Str "attachment."]]]

test/ipynb/simple.ipynb

@@ -45,7 +45,12 @@
   },
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "tags": [
+     "foo",
+     "bar"
+    ]
+   },
    "source": [
     "Image\n",
     "-----\n",

test/ipynb/simple.out.native

@@ -8,6 +8,6 @@ Pandoc (Meta {unMeta = fromList [("jupyter",MetaMap (fromList [("nbformat",MetaS
  [Header 2 ("pyout",[],[]) [Str "Pyout"]]
 ,Div ("",["cell","code"],[])
  [CodeBlock ("",["python"],[]) "from IPython.display import HTML\nHTML(\"\"\"\n<script>\nconsole.log(\"hello\");\n</script>\n<b>HTML</b>\n\"\"\")"]
-,Div ("",["cell","markdown"],[])
+,Div ("",["cell","markdown"],[("tags","[\"foo\",\"bar\"]")])
  [Header 2 ("image",[],[]) [Str "Image"]
  ,Para [Str "This",Space,Str "image",Space,Image ("",[],[]) [Str "the",Space,Str "moon"] ("lalune.jpg",""),Space,Str "will",Space,Str "be",Space,Str "included",Space,Str "as",Space,Str "a",Space,Str "cell",SoftBreak,Str "attachment."]]]