Support Collapsed Text

[mtbaqer]

Description

Adds VSCode implementation of LSP's collapsed text.
Allows for custom collapsed text instead of the default ..., and the ability to start folding anywhere in the start line not only at the very end. See the demo below.

Demo

Issues

• Fixes [folding] custom folding text for folded ranges #70794.

Should make following issues trivial to solve:

• [folding] Collapse ending brace to the same line #3352
• [folding] Show number of lines folded #130250
• [folding] show comment first line for folded sections #31966

Does a lot of heavy lifting for (but still requires some work):

• Support folding ranges inside a line #50840

Changes

• Adds two fields to almost all inner folding interfaces/classes (FoldingRange, FoldingRegion, etc.):

  • collapsedText: text to display
  • startColumn: where the folding should start at the start line. More details here.

• Changes FoldingDecorations to dynamically construct collapsed decorations to include collapsed text (currently little messy, will make a future refactor PR to reduce the size of this one).

• Introduces new InlineFoldingRange class to support the custom startColumn. Currently only supports always folding to the end of the line.

• Adds new hideContent field to ModelDecorationOptions to support InlineFoldingRange.

• Modifies ModelLineProjection, ModelLineProjectionData and related classes to support inlineFoldingRange.

• Adds new test cases and modifies current ones for most classes touched.

Note: The current implementation assumes InlineFoldingRange decorations are located in the same InjectedText decoration tree. This can be changed in future updates.

VSCode Language Server

A new PR against vscode-languageserver-node is needed to support providing ranges through the language server and to update the capability.

[mtbaqer]

@microsoft-github-policy-service agree

[mtbaqer]

@aeschli any updates on this?

[aeschli]

Thanks @mtbaqer, this is an impressive change, that will take a while to process and review. We need @alexdima to look at the editor changes, but unfortunately he's out for the month. Or maybe @hediet can check it out?

[daiyam]

Is there any updates? This PR is a must have. Thanks @mtbaqer

[hediet]

I had a look at the PR now.

I am very impressed by the work and I can see that it took a lot of effort to implement this feature!

However, because this part of the editor is so complicated, we have to be very careful with how such features are implemented.
I think we should split up this feature into a proper implementation of the hideContent flag for decorations and then the folding feature on top of that.

The implementation of the hideContent flag in this PR misses some edge cases and doesn't properly implement the flag, as it only supports hiding content from a given offset until the end of the line.

I think the hideContent flag and injected text together should be implemented as view edits to simplify the implementation. A single view edit would replace a range with text. That range can be non-empty to hide content and the text can be non-empty to insert text.
That way there wouldn't be confusion around folding indices within injected text.

[mtbaqer]

@hediet Thanks for taking the time to look over the PR.

I 100% agree that fully implementing the hideContent flag (which is basically #50840) then doing the custom collapsed text #70794 is the better approach. The reason that did not happen was to reduce the amount changes required to achieve the goal of the PR which was #70794.

Given your knowledge of the codebase, if you think a full implementation of inline folding is absolutely required, then I understand. However, as much as I would love to implement #50840, I'm afraid I would not be able to anytime soon (I'm graduating soon and still in the middle of a job search). Anyone is more than welcome to build on top my current InlineFoldingRange implementation to do it.

On the other hand, if there's anything else we can do to this current PR to provide a solution for #70794 that can be merged with much less work required, I would be more than happy to help with what I can.