[folding] language-aware folding

[aeschli]

The current implementation of folding uses an indentation based folding strategy that is unaware of the language it works on. Knowledge on the underlying language allows us to solve the following requests:

• [folding] Cannot code fold empty functions [folding] Cannot code fold empty functions #3349
• [folding] Collapse ending brace to the same line [folding] Collapse ending brace to the same line #3352
• [folding] Folded block comments should show */ [folding] Folded block comments should show */ #3350
• [folding] should not fold whitespace after function [folding] should not fold whitespace after function #3353
• [folding] Add code folding for markdown based on heading level [folding] Add code folding for markdown based on heading level #3347
• [folding] [lua] Weird code folding with Lua [folding] [lua] Weird code folding with Lua #3602
• [folding] Collapse code block ignore comments inside this block [folding] Collapse code block ignore comments inside this block #3957
• [folding] Code Folding: support golang multiline strings [folding] support golang multiline strings #5994
• [folding] Optionally fold chained method calls [folding] Optionally fold chained method calls #6991

[rkeithhill]

Another issue I don't see in that list is user-configured folding like this example from C#:

#region Public methods
...
#endregion

In the PowerShell extension we would like to provide this same sort of feature the same syntax as what C# uses which, in PowerShell, looks like a "special" comment.

[fromthewoods]

PowerShell block comment folding is weird in the Insider build 0.10.10.
<#
Comments here
and here
#>
Broken: http://i.imgur.com/M6Ay1vl.gif
It should fold around the <# + #>
Like this: http://i.imgur.com/HFRHJJL.gif
https://blogs.msdn.microsoft.com/powershell/2008/06/14/block-comments-in-v2/

[fromthewoods]

Now I understand. It's the indentation level. Language-aware folding ftw!

[bgelens]

PowerShell here-string breaks folding logic.
Here-string end marker must be placed on first column of new line.

As you can see, the function isn't folded correctly anymore although folding was done on the function keyword. Code after the here-string stays visible as well.

[rkeithhill]

Yeah, I think for VSCode to give the best experience for code-folding they're definitely going to need help from the various language extensions/services.

[daviwil]

Either that or we're going to have to tweak the PowerShell syntax definition to jive with their folding model a little better. May need some pointers from Martin about what we can do to improve folding if the tmLanguage definition is a factor.

[aeschli]

@rkeithhill For the moment there's nothing you can tweek on your side until we allow languages to control code folding.

[jgeorgeson]

As another example, Ant build.xml files can have large text blocks where the content doesn't adhere to indentation of the XML. Such as

    <echo file="myfle.txt">
totally unindented
text
       goes here
 and breaks VS Code folding
    </echo>

[felixfbecker]

PowerShell here-string breaks folding logic.
Here-string end marker must be placed on first column of new line.

the same thing happens with PHP heredoc.

Also, sections in INI files cannot get folded by indentation

[nfloersch]

I'm probably way out of my depth here...

User-controlled folding - with "regions" - seems fairly straight-forward to define. The editor needs to only be language aware enough to know how each language shows comments. Then if a comment starts with "region" or "endregion" such as...

#region ... #endregion
//region ... //endregion
/region/ ... /endregion/
'region ... 'endregion
---region ... ---endregion

...

You treat the content in-between as a region. It seems like creating a list of all supported language comment syntaxes is the only thing necessary.

[pcgeek86]

Definitely need this resolved for PowerShell

[LeThiHyVong]

Atom's code folding based on indentation. But the next release (1.25) new parsing system Tree-sitter is added. I tried roughly and it's ok on small files.
May VSCode follow?
atom/atom#16299

Update: Seem like VSCode team plan to work on their own https://code.visualstudio.com/updates/v1_21#_folding

[rcjsuen]

I saw that a new experimental API was introduced in VS Code 1.21. Thank you for looking into this.

Are there any plans to give control as to which line is shown after the content is folded? For example, in VS Code, the source files look like this at the top:

/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

Current folding behaviour:

/*--------------------------------------------------------------------------------------------- ...

Proposed folding behaviour:

...  *  Copyright (c) Microsoft Corporation. All rights reserved. ...

export interface FoldingRange {

	/**
	 * The start line number
	 */
	startLine: number;

	/**
	 * The end line number
	 */
	endLine: number;

	/**
	 * The line to show when the region is folded. If this is
	 * unspecified, then startLine will be shown.
	 */
	visibleLine?: number;

	/**
	 * The actual color value for this folding range.
	 */
	type?: FoldingRangeType | string;
}

[unional]

@rcjsuen your request is similar to #19912

[rcjsuen]

Thank you for the info, @unional.

I also found #31966.

[pr-yemibedu]

Hello,
There would need to be a really strong formatter to shrink the excessive parts of the comments to get at such useful information. That may not be the exact case now, but I wanted to brain dump it. Most typical, lines with at least one letter or number is a high candidate for keeping to favor that useful preview style. It would handle most scenarios. Thank you. Good day.

[SunOfHomeBoy]

code fold logic have a question

[aeschli]

@SunOfHomeBoy Please file a separate issue with the VSCode version and the sample code.

[beachdweller]

Dear all,

I think I have not seen this example here yet. (Please let me know if other post discussed this already)

[pr-yemibedu]

Hello,
@Autodrive , It not a new notion to the old problem of only having indentation as the folding signal. There is now experimental syntax support possible in the mainline. It needs extension author help for the vast languages out there. Only HTML, JSON, Markdown, CSS, LESS and SCSS come available out of the box. So hopefully there can be a resolution to many of these scenarios issues. Thank you. Good day.

[aeschli]

Thanks @pr-yemibedu, correct.
In the coming release language extension authors now can provide folding range providers that are based on the language syntax. Please file issues against your favourite language extension provider to add support for your language.

[paul-xtr]

The cold foldering section of the interactive playground still says that code folding is based on indentation and doesn't mention the new language aware folding. It probably should be reworded.

[Thaina]

Seem like it's could be done as extension now

https://code.visualstudio.com/updates/v1_23#_folding-provider-api

[peon501]

Any news on

Iam w8ting for months #37494

[aeschli]

So the API is now available, so language extensions can add language aware folding. I reopened #37494 to continue the discussion.