[Feature Request] Skip formatting doc comments altogether when mixing sugared and de-sugared doc comments

[stepancheg]

Input:

//! <details open>
//!     <summary>Example 1</summary>
//!
//! ```
#![doc = "test()"]
//! ```
//!
//! </details>
//!
//! <details open>
//!     <summary>Example 2</summary>
//!
//! ```
//! example(2);
//! ```
//!
//! </details>

rustfmt +nightly --config format_code_in_doc_comments=true

Outputs:

//! <details open>
//!     <summary>Example 1</summary>
//!
//! ```
#![doc = "test()"]
//! ```
//!
//! </details>
//!
//! <details open>
//!     <summary>Example 2</summary>
//! ```
//! example(2);
//! ```
//!
//! </details>

Note no empty line before second example. So rustdoc of output looks like this:

Empty lines before backticks are important for Markdown.

Rustdoc uses commonmark

HTML blocks in commonmark must end with empty line:

End condition: line is followed by a blank line

rustfmt 1.7.0-nightly (ca663b06 2024-01-08)

[ytmimi]

I'm pretty sure the use of #![doc = "test()"] is throwing rustfmt off. This feels very similar to #5420.

//! <details open>
//!     <summary>Example 1</summary>
//!
//! ```
//! test()
//! ```
//!
//! </details>
//!
//! <details open>
//!     <summary>Example 2</summary>
//! ```
//! example(2);
//! ```
//!
//! </details>

[stepancheg]

@ytmimi that issue you linked is closed.

The problem with this case is that it rustfmt damages valid code, so I believe some solution is needed (for example, just skip formatting of comments if they have #[doc]).

[ytmimi]

The linked issue is closed because of technical limitations on rustfmt's side. Maybe it's possible to skip formatting altogether if there's a mix of sugared and de-sugard doc comments. I'll reopen this one for now as a feature request, but I'll be honest this is pretty low priority, and I don't anticipate the rustfmt team working on this directly.