Plugin output is not being rendered

[jessicah]

Describe the bug

context I've written a port of markdown-it-abbr to python, but when used with MyST-Parser, the replacement tokens are missing, due to an error of WARNING: No render method for: abbr [myst.render].

expectation In the rendered HTML, I expected the <abbr> HTML tag and content to be output.

E.g. the following markdown:

*[HTML]: HyperText Markup Language
*[W3C]: World Wide Web Consortium

The HTML specification is maintained by the W3C.

should generate:

<p>The <abbr title="HyperText Markup Language'>HTML</abbr> specification is maintained by the <abbr title="World Wide Web Consortium">W3C</abbr>.</p>

bug Instead, it generates:

<p>The specification is maintained by the .</p>

I added print(nodes) at https://github.com/jessicah/mdit-py-abbr/blob/main/mdit_py_abbr/index.py#L157, and it showed up fine in console:

[Token(type='text', tag='', nesting=0, attrs={}, map=None, level=0, children=None, content='The ', markup='', info='', meta={}, block=False, hidden=False), Token(type='abbr_open', tag='abbr', nesting=1, attrs={'title': 'HyperText Markup Language'}, map=None, level=0, children=None, content='', markup='', info='', meta={}, block=False, hidden=False), Token(type='text', tag='', nesting=0, attrs={}, map=None, level=0, children=None, content='HTML', markup='', info='', meta={}, block=False, hidden=False), Token(type='abbr_close', tag='abbr', nesting=-1, attrs={}, map=None, level=0, children=None, content='', markup='', info='', meta={}, block=False, hidden=False), Token(type='text', tag='', nesting=0, attrs={}, map=None, level=0, children=None, content=' specification is maintained by the ', markup='', info='', meta={}, block=False, hidden=False), Token(type='abbr_open', tag='abbr', nesting=1, attrs={'title': 'World Wide Web Consortium'}, map=None, level=0, children=None, content='', markup='', info='', meta={}, block=False, hidden=False), Token(type='text', tag='', nesting=0, attrs={}, map=None, level=0, children=None, content='W3C', markup='', info='', meta={}, block=False, hidden=False), Token(type='abbr_close', tag='abbr', nesting=-1, attrs={}, map=None, level=0, children=None, content='', markup='', info='', meta={}, block=False, hidden=False), Token(type='text', tag='', nesting=0, attrs={}, map=None, level=0, children=None, content='.', markup='', info='', meta={}, block=False, hidden=False)]

So the token stream itself seems correct. Also, using markdown-it-py directly works correctly.

I did try adding a render method, but it had no effect. E.g.:

md.add_render_rule("abbr", abbr_render)

and

def abbr_render(self, tokens, idx, options, env):
    return f'<abbr title="{tokens[idx].attrGet("title")}">{tokens[idx].content}</abbr>'

Reproduce the bug

I've created an example repo: https://github.com/jessicah/myst-demo

make [all] runs sphinx-build, and make test runs the test file.

List your environment

myst_parser: 0.18.1 sphinx: 5.3.0 docutils: 0.17.1 markdown_it: 1.1.0

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[jessicah]

It seems like perhaps MyST-Parser's DocutilsRenderer is the culprit, using a fixed list of renderers?

See: https://github.com/executablebooks/MyST-Parser/blob/master/myst_parser/mdit_to_docutils/base.py#L102-L106

This might also explain what was going wrong in my WIP patch in https://github.com/executablebooks/MyST-Parser/issues/632

[jessicah]

Ohh, I see, it's because the overridden render methods produces docutils AST nodes, correct? And the plugins produce HTML strings, which is why all the currently supported plugins have their equivalent render_xyz methods in the DocutilsRenderer class. Still, an easy way to extend them would be useful... hmm.

[chrisjsewell]

Heya, yep indeed myst-parser intentionally does not expose markdown-it-py as the underlying markdown parser, it would not be maintainable to support such an API.

If you want to have a look at contributing your plugin to https://github.com/executablebooks/mdit-py-plugins, we can look to add it to myst-parser as an extension 😄 (there is already a node type for it, so should not be too difficult https://docutils.sourceforge.io/docs/ref/doctree.html#abbreviation)

[jessicah]

@chrisjsewell ah, yeah, I was just at that docutils link, although not quite sure how to write the render_abbr method in my python code.

I figured I can make a custom renderer by subclassing myst_parser.mdit_to_docutils.sphinx_.SphinxRenderer, and calling create_md_parser(config, CustomRenderer):

class CustomRenderer(SphinxRenderer):
    def render_abbr(self, token: SyntaxTreeNode) -> None:
        print(token)

class CustomParser(MystParser):
    def parse(self, inputstring: str, document: nodes.document) -> None:
        config: MdParserConfig = document.settings.env.myst_config
        # . . .         
        parser = create_md_parser(config, CustomRenderer)
        # . . . 

def setup(app):
    from myst_parser.sphinx_ext.main import setup_sphinx

    setup_sphinx(app, load_parser=False)
    app.add_source_suffix(".md", "markdown")
    app.add_source_parser(CustomParser)

I'm at least getting the print outputing SyntaxTreeNode(abbr) in my test, so it's just figuring out the final piece...

Some tips on what I should be producing in render_abbr would be great, and I can make PRs for both :)

[chrisjsewell]

Yeh no worries, if you get the PR into executablebooks/mdit-py-plugins, I should be able to take care of the myst-parser side (it should be relatively straight forward)

[jessicah]

https://github.com/executablebooks/mdit-py-plugins/pull/63

[jessicah]

@chrisjsewell any chance you can help me out with the myst-parser side as the plugin exists atm? I'd like to be able to start using in my own project ;-)