How to use generated output as the body of an outer code block?

[sisp]

I'm trying to generate content for a fenced code block and thought markdown-exec could do just that, but I'm hitting a wall.

I'd like to render a Vega-Lite chart in MkDocs using mkdocs-charts-plugin. But instead of hardcoding the Vega-Lite JSON document, I'd like to generate it, e.g. using some inline Python code or using a shell command. Before actually trying it out and seeing it fail, I thought this was going to work:

````vegalite
```python exec="1"
# Imagine a real function that generates a Vega-Lite JSON document
print('{"$schema": "https://vega.github.io/schema/vega-lite/v5.json", ...}')
```
````

But mkdocs-charts-plugin fails to render the Vega-Lite JSON document because it receives literally this

```python exec="1"
# Imagine a real function that generates a Vega-Lite JSON document
print('{"$schema": "https://vega.github.io/schema/vega-lite/v5.json", ...}')
```

instead of the result from executing this Python code.

After thinking about this problem a little, it probably wouldn't be a good idea – if technically possible at all – to always render inner code blocks with exec="1" and pass the output to the outer code block because then writing documentation that shows a code block with exec="1" wouldn't be possible (it would be rendered and not left untouched).

That said, is there any way to do what I'm trying to achieve, ideally in a generic way without needing to add explicit support for the vegalite fence (which I could do of course – if you accepted the contribution –, but it wouldn't scale to other similar use cases)?

[pawamoy]

Hey @sisp, happy to see you here 😄

So, yeah, your reasoning is correct, we can't execute inner code blocks if the outer is not also executed. We cannot even detect that the inner block should be executed: we rely on the PyMDown Superfences extension (not regular expressions or other similar approaches), so we only ever see outer code blocks: the inner code blocks are just seen as contents of the outer code blocks.

Now, I believe what you want to achieve is possible. Try this:

```python exec="1" result="vegalite"
# Imagine a real function that generates a Vega-Lite JSON document
print('{"$schema": "https://vega.github.io/schema/vega-lite/v5.json", ...}')
```

This simply tells Markdown Exec to wrap the output of your executed code block in a vegalite code block, and render it again from Markdown to HTML 🙂

[sisp]

OMG, I can't believe I missed this option in the docs. 🤦 It's the solution to my problem. 👌 Sorry for the bother because of my not reading the docs properly. 🫣 markdown-exec is such an amazing MkDocs plugin! 🚀

[pawamoy]

No worries haha, and thanks ❤️ !