[clangd] Add folding ranges for #ifdef sections

[torshepherd]

Folding ranges (or whatever the corresponding LSP term is) allow users to 1. See the top line of the range as they scroll down stickily and 2. Fold entire ranges of code they don't care about

#ifdef and other preprocessor conditional blocks are well suited for this because 1. devs would benefit from seeing things like #ifdef clang following their cursor when they're very far down in a large file, and 2. e. g. A Linux dev might want to collapse an entire #ifdef WINDOWS section that's irrelevant to their work.

[llvmbot]

@llvm/issue-subscribers-clangd

Author: Tor Shepherd (torshepherd)

Folding ranges (or whatever the corresponding LSP term is) allow users to 1. See the top line of the range as they scroll down stickily and 2. Fold entire ranges of code they don't care about

#ifdef and other preprocessor conditional blocks are well suited for this because 1. devs would benefit from seeing things like #ifdef clang following their cursor when they're very far down in a large file, and 2. e. g. A Linux dev might want to collapse an entire #ifdef WINDOWS section that's irrelevant to their work.

[torshepherd]

Related: clangd/clangd#310, clangd/vscode-clangd#297, clangd/clangd#1661, clangd/clangd#2059,

#80592

[torshepherd]

Duplicate