Hiding execution options for Rust in the output

[Ablu]

Description

I am using the jupyter engine with evcxr. That works super well. But for one code cell I want to show error messages.
That works like this:

---
format: revealjs
execute:
  echo: true
---

```{rust}
#| error: true
fn foo(bar: TypeMissingCausesCompileError) {}
```

It looks as if the #| has an effect (the cell output includes the error). It also looks like the comment is trimmed before passing to the engine. But the #| error: true also gets printed in the output cell.

Any way I can get just the code without the #| error: true?

[mcanouil]

Your example does not use Jupyter, it defaults to knitr as the engine.

YAML option respect the "comment symbol" + "pipe" syntax.
# is not the comment symbol for Rust. // is.

[Ablu]

Does your kernel knows how to deal with errors?

It seems to work as I expect it when setting the #| error: true. My only problem is that the config line also gets emitted when setting the echo: true globally.

Screenshot:

So I assumed it would be quarto doing the filtering here?

rustc does not complain about the #| here, so it does not seem to arrive on the engine. But at the same time it definitely has an impact whether I add the #| error: true or not :). It feels like it gets detected to pick up the error handling and sending to the engine but not when emitting the code cell into the final document.

From what I have seen the rust kernel is not compatible with code cell level error option. The "workaround" is to set it at global level:

---
execute:
  error: true
---

Sure, that works! Though, I hoped to get it working at a cell level so I do not silently introduce errors elsewhere :).

[mcanouil]

If the kernel emits all this as the same output, then Quarto cannot do anything about it.
So, the answer is likely on the kernel or Rust side.

[mcanouil]

It seems to work as I expect it when setting the #| error: true. My only problem is that the config line also gets emitted when setting the echo: true globally.

It does not work since as per your screenshot the option is considered as code.

# is the default comment symbol when none is known by Quarto for a language.
But rust comment symbol is known:

• quarto-cli/src/core/jupyter/jupyter.ts

  Line 1245 in 70148df

  rust: "//",

[Ablu]

If the kernel emits all this as the same output, then Quarto cannot do anything about it.
So, the answer is likely on the kernel or Rust side.

Hm. I am still a bit confused as it looks to me as if the option is stripped before the code ends up in the kernel:

1. The line numbers do not include the setting line
2. The setting line has an impact on whether the error is presented in the output vs quarto throwing an error
3. running a raw Jupyter and leaving the #| error: true line in gives me a syntax error when attempting to treat it as rust code

But thanks a lot for your input! I will try to find some time to debug quarto and figure out what is going on :)

[mcanouil]

I agree something is weird here with the rust kernel which I did not see with other kernels so far.
Unfortunately, I'm not a Jupyter internals expert.