Feature Request: Folding regions for Rust

[PaulHale]

Folding regions for Rust

The following languages currently have markers defined:

TypeScript/JavaScript: //#region and //#endregion and //region and //endregion
C#: #region and #endregion
C/C++: #pragma region and #pragma endregion
F#: //#region and //#endregion
Powershell: #region and #endregion
VB: #Region and #End Region
CSS/Less/SCSS: /*#region*/ and /*#endregion*/
Coffeescript: #region and #endregion
PHP: #region and #endregion
Bat: ::#region and ::#endregion

Can we please have this functionality for Rust code?
Rust: #region and #endregion would suffice

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• [folding] select line with folding should include folded range (#51232)
• [folding] Hover can show region description on #endregion (#38149)
• region navigator (#51738)
• #region and #endregion last state is not saved (#42217)
• Typescript region folding does not work when syntax-aware folding is enabled (#52650)

[isidorn]

This works for me nicely if the #region and #endregion are indented all the way to the left. However if they are a bit indented it does not work. @aeschli is this expected?
Here's an example where it is not working (notice the indentation)

fn main() {
    // The statements here will be executed when the compiled binary is called

	#region
 	///my region
	#endregion

    // Print text to the console
    println!("Hello World!");
}

[aeschli]

Sounds like a bug to me.

[PaulHale]

@isidorn it does work if the code within the #region #endregion is also indented. Kind of forces you to indent your code within regions which I personally like. Not sure if this is by design though.

[aeschli]

The PR added only// region and // endregion as folding regions. For consistency we should also support // #region and // #endregion. That was the original request and what @isidorn tried.

[bpasero]

Verified. But the code in the region has to be indented for this to work.

[isidorn]

@bpasero read my comment from above, this should also work if the code is not indented as well (I justr tried with latest insiders and it is not working). Reopening so @aeschli can decide if this is intended

[DJMcNab]

A few thoughts:

• Sorry that I didn't support //#region and friends - it might be worth just copying the Typescript ones into Rust: https://github.com/Microsoft/vscode/blob/1eb0b5bc91f637940facfd0c509a2c35b16f3969/extensions/typescript-basics/language-configuration.json#L29-L34
  However, the Rust Style Guide says that a single space after comment markers should be used. I don't know if this we should require this or just leave it up to tools such as rustfmt. It might be worth asking @nrc's opinion for this

• I should have done this originally in add rust region comments (#55648) #57069, but only made that PR quickly and didn't test it properly.

• I don't think Rust supports # comments:
  See @isidorn's code in the playground. Try pressing Run and see it error.

• Also, once this is done, if the issue with indentation still reproduces in Rust, can we see if it reproduces in Typescript as the region comments would be the same. With some initial testing, I cannot reproduce.

[aeschli]

With my fix this should work also indented.

When testing always use content with the same or smaller indent than the #region. Otherwise you might see the regular indentation based folding regions.

@bpasero What was your example?

[bpasero]

@isidorn the one from isidor

[aeschli]

@bpasero Ah, his example is missing the // before region.

[nrc]

However, the Rust Style Guide says that a single space after comment markers should be used. I don't know if this we should require this or just leave it up to tools such as rustfmt. It might be worth asking @nrc's opinion for this

We do prefer a space after a comment, however, we use //! for doc comments, so there is precedent for not using a space where there is punctuation which is changing the 'kind' of a comment. On the other hand, these are used //! words not //!words so //#region would still be different.

In general, Rust and it's tools do not have any 'significant' comments and when people have tried to use them there has usually been a negative reaction. So I don't think using //#region or // #region would be popular. However, I can't think of a better way to do it. The Rust way would be #[vscode::region], but these attributes can only be used on specific AST nodes, they can't be used to mark a point in a file. I don't know of a good solution, so perhaps comments are OK.