support of cell metadata in markdown

[cleemesser]

I am interested in supporting notebook cell metadata in the markdown file.This would have benefits:

• It would maintain metadata like slideshow information for cells and allow one to write a slide show in markdown originally.
• The would allow true round trip fidelity ipynb -> markdown -> ipynb

I am not sure about the best way to do this, but I can imagine abusing markdown links somewhat

each markdown cell would be allowed to have a "comment:"

[//]: # ( "cell_type": "markdown", "metadata": { "slideshow": { "slide_type": "slide"} } )
### The markdown content level three header
content plain text...

The code blocks would be handled as they are in notedown, but would add an optional metadata tag:

```{.python, "metadata" : {"collapsed": false, "slideshow": { "slide_type": "fragment"} } }
import numpy, pandas
y = 3 * 4
```

This may be an answer to #47 I am not married to the idea of using this particular system, but it would seem it would be ignored by a typical common-mark/markdown renderer and would not be too hard to implement.

[sje30]

hi @cleemesser - I have other reasons for working on this project (supporting Julia, R), so roundtripping sounds like a great idea to me. joint project?!?

[sje30]

p.s. you know more python than me!

[cleemesser]

Sounds good. I have forked aaren's code and am messing with it as a prototype.

• looks like there is a problem with embedding metadata in markdown attributes as used with the fenced code in notedown, at least as implemented in the PandocAttribute class. It appears to mangle them when it tries to read them back.
• one way around this: have every cell have a [//] header, just like the markdown cells

Will implement ipynb -> markdown first as this is easiest using aaren's code. See https://github.com/cleemesser/notedown metadata branch

[aaren]

I'm not really sure about the best way to do this, and I'm a bit reluctant as I have very little time to maintain this any more, but things to consider are Pandoc's header_attributes and fenced_divs http://pandoc.org/MANUAL.html

Closing for now.