Positron assistant code completion bugs out quarto code chunks

[tacaro]

System details:

Positron and OS details:

Positron Version: 2025.12.1 build 4
Code - OSS Version: 1.106.0
Commit: f70a9bc
Date: 2025-12-05T20:53:14.100Z
Electron: 37.7.0
Chromium: 138.0.7204.251
Node.js: 22.20.0
V8: 13.8.258.32-electron.0
OS: Darwin arm64 21.6.0

Session details:

R 4.5.1
Positron Assistant with Github Copilot Completion Provider

Describe the issue:

Github copilot code completion will indent the triple backticks '```' used to demarcate code chunks in quarto documents. This will cause errors with code execution when running lines of code or code chunks. These problems will show up in the 'Problems' tab as "No Symbol named '```' in scope.

Steps to reproduce the issue:

This issue is difficult to reproduce 'in the wild' because it relies on LLM completion interfering with the triple backticks, which it does not reliably do. The error I encounter can be reproduced manually with the following steps:

1. Create a quarto document
2. Either with code completion or manually, indent the triple backticks at the end of a quarto R code chunk
3. With any sample code inside the code chunk, attempt to run the code line-by-line with whatever keyboard shortcut you have for this (for me, it's CMD+Enter).

(You may be able to reproduce the entire problem by coding one line above the triple backticks with an LLM completion tool for a long enough time period...)

Expected or desired behavior:

Code will not execute properly when these backticks are indented (which is often done inadvertently by Positron assistant/Github copilot completions)

Were there any error messages in the UI, Output panel, or Developer Tools console?

See above screenshot.

[juliasilge]

I haven't been to make get Copilot completions to do this exactly so far, although certainly if you indent the triple backticks you no longer have valid Quarto code cells. It is expected that you can't use statement execution if you have mangled code cells, perhaps something like this:

---
title: "My simple Quarto file"
format: html
---

## Make a plot

You can embed plots in a Quarto file, for example:

```{r}
#| echo: false
plot(faithful)
  ```

## Cool math

Or you can do simple calculations:

```{r}
1 + 1
```

Would you say you are asking about why statement execution via Cmd+enter doesn't work in this situation? Or why Copilot completions may have mangled the code cells? On the second, I haven't been able to see that myself so far (completions in a code cell are sensible, completions out of a code cell as sensible), but certainly it's not out of the realm of possibility.

[tacaro]

Thanks for your reply Julia! Yes, definitely more curious about the second aspect you identified – I can understand why Cmd+Enter does not function in this situation but more curious how copilot completions interfere with the backticks.

This is indeed a niche and difficult-to-replicate issue, but it has come up enough times in the past few weeks that I've found myself spending a decent chunk of time hunting through .qmds for indented backticks, so I figured it could be helpful to bring up if others have similar issues.

(I wonder if ensuring no indentations for triple backticks is something the Air formatter can address?)

[juliasilge]

We would definitely be interested in any steps you think are more likely to cause Copilot completions to behave this way, so that we might be able to understand when it might be happening.

In terms of how to identify problems like this in Quarto syntax, Air really only knows about R code (not Quarto code); it works in .qmd files because it has access to only the R code cells. However, the Quarto team is working on a new parser that will be useful in exactly that situation:
https://github.com/quarto-dev/quarto-markdown
The idea is that it will be able to parse your .qmd as a whole and providing diagnostics and linting for any problems in your file. A tool like that won't stop Copilot from generating completions that might not be valid Quarto syntax, but it will tell you when it happens. It would solve the problem you mention about hunting through your long file for the problem. It's not quite ready for prime time but I am excited about it!

[tacaro]

Cool! Excited to see that deployed. In the meantime I'll keep investigating to see if I can figure out what exactly gets copilot to futz with the code chunk delimiters. Should I close this issue (and is it possible to re-open it if I find out more?) or would you prefer I keep it open?

[juliasilge]

I think let's close for now; we can definitely re-open and/or keep our eyes peeled for similar reports. Thank you!