Pandoc Self-Contained HTML files with embedded CSS links

[kmader]

I have an RMarkdown report exporting to HTML (via Pandoc) and a few lines adding relevant css files to the report, specifically

<link rel="stylesheet" href="leaflet.css" />

causes pandoc to produce the error message

pandoc: Could not fetch html-demo/#default#VML

Since it is trying to parse this line in the css file to make it self-contained

.lvml {
    behavior: url(#default#VML);
    display: inline-block;
    position: absolute;
    }

which does not refer to a physical file.

Pandoc should ignore such tags in css files (initial issue posted in rmarkdown: rstudio/rmarkdown#418)

[nkalvi]

@kmader Would you please post a complete example along with your Pandoc's version and the complete command?

[jgm]

@nkalvi - although this is usually important to have, I think in this
case it is already clear enough what the problem is and how to solve it.

+++ nkalvi [Apr 27 15 06:40 ]:

@kmader Would you please post a complete example along with your Pandoc's version and the complete command?

[nkalvi]

Thanks @jgm - I realized it after a few minutes.

[kmader]

So in the case I am using (which is probably not completely proper usage of the pandoc tools) actually has the
<link rel="stylesheet" href="leaflet.css" type="text/css" /> portion inside the md file rather than being specified as a pandoc -c argument.
This is the case because it is not a style-sheet for the entire document rather a style sheet being included for a component or widget within the document.

[mpickering]

Surely you mean to use the --self-contained command?

[kmader]

Thanks @nkalvi @mpickering , here is a better working example

• pandocTest.md

# Hi
<link rel="stylesheet" href="pandocTest.css" />
# Bye

• pandocTest.css

.lvml {
    behavior: url(#default#VML);
    display: inline-block;
    position: absolute;
    }

Executed command

pandoc pandocTest.md --self-contained -o pandocTest.html

Error message: pandoc: Could not find data file ./

[jgm]

I think the fix is easy, in `cssURLs` in `Text.Pandoc.SelfContained`, we should check to see if the URL starts with `#`, and if it does, just return the original.

[nkalvi]

Sorry for not noticing it involved self-contained; Matt, thanks for pointing it out.

@jgm @mpickering would this be an acceptable fix?
I feel checking for URI reference instead of just # may be more future-proof.

In Text.Pandoc.SelfContained

import Network.URI (isURI, escapeURIString, URI(..), parseURI, isURIReference)

cssURLs :: MediaBag -> Maybe String -> FilePath -> ByteString
        -> IO ByteString
cssURLs media sourceURL d orig =
  case B.breakSubstring "url(" orig of
       (x,y) | B.null y  -> return orig
             | otherwise -> do
                  let (u,v) = B.breakSubstring ")" $ B.drop 4 y
                  let url = toString
                          $ case B.take 1 u of
                                 "\"" -> B.takeWhile (/='"') $ B.drop 1 u
                                 "'"  -> B.takeWhile (/='\'') $ B.drop 1 u
                                 _    -> u
                  let url' = if isURI url
                                then url
                                else d </> url
                  rest <- cssURLs media sourceURL d v
                  if not (isURIReference url') -- Ignore behavior: url(#default#VML) etc.
                    then
                      return $ x `B.append` "url(" `B.append` (fromString url) `B.append` rest
                    else do
                      (raw, mime) <- getRaw media sourceURL "" url'
                      let enc = fromString $ makeDataURI mime raw
                      return $ x `B.append` "url(" `B.append` enc `B.append` rest

[nkalvi]

@kmader You may already be aware of the --include-in-header option. I'm not sure whether it would be a feasible temporary workaround in your case (to include portions that result in error).

`-H` *FILE*, `--include-in-header=`*FILE*

:   Include contents of *FILE*, verbatim, at the end of the header.
    This can be used, for example, to include special
    CSS or javascript in HTML documents.  This option can be used
    repeatedly to include multiple files in the header.  They will be
    included in the order specified.  Implies `--standalone`.

[jgm]

@nkalvi, isURIReference doesn't test for what we need to test for. Haddocks say:
"Test if string contains a valid URI reference (an absolute or relative URI with optional fragment identifier)."

[jgm]

(Sorry - that last commit should not have referenced this issue.)