Highlight on hover in very large file hangs; 100% CPU and memory grows

[Atemu]

I work on Nix a lot. When I open Nixpkgs' all-packages.nix (1.4MiB) with the nixd server and hover over an instance of callPackage, nixd tells emacs to highlight that keyword and then emacs goes spinning. It can be cancelled but that results in highlighting of callPackage instances being stuck.

[stderr] I[14:15:13.101] 76380: <-- textDocument/hover(149)
[stderr] I[14:15:13.101] 76380: --> call attrset/attrpathInfo(2092)
[stderr] I[14:15:13.101] 76380: <-- textDocument/documentHighlight(150)
[stderr] I[14:15:13.101] 76380: <-- reply(2092)
[stderr] I[14:15:13.101] 76380: --> reply:textDocument/hover(149)
[server-reply] (id:149) Thu Apr 25 14:15:13 2024:
(:id 149 :jsonrpc "2.0" :result
     (:contents nil :range
                (:end
                 (:character 21 :line 4963)
                 :start
                 (:character 10 :line 4963))))
[stderr] I[14:15:13.224] 76380: --> reply:textDocument/documentHighlight(150)

Is it attempting to highlight all 15k instances of callPackage in the buffer? Can I make it not do that somehow? I only need the highlighting in the visible portion, the rest can be loaded on-demand.

Alternatively, can I turn of highlight on hover in certain files only? Or ideally in very large files past a certain size.
If you can't disable just highlighting (that appears to be the primary performance limitation), can you disable eglot in certain paths only (or past a certain size)?

[joaotavora]

Is it attempting to highlight all 15k instances of callPackage in the buffer?

Possibly. Let's confirm that by your experiment after M-x profiler-start (choose the "CPU+MEM" profiler), then M-x profiler-stop after you're done experimenting, then M-x profiler-report, and press RET (or maybe C-u RET)` to expand a selected interesting subtrees. Then post the result here.

But perhaps , and very importantly, before doing that, make sure you report your Emacs version, your Eglot version, and desirably everything (and I really do mean everything) requested in https://www.gnu.org/software/emacs/manual/html_node/eglot/Reporting-bugs.html