badrpc message during find definition

[delitrem]

I use expert (version is v0.1.0-rc.5, taken from here) with GNU Emacs 30.2, eglot and eglot-booster under Guix System (the NixOS equivalent with Guile Scheme instead of Nix DSL).

Sometimes I get the following message:

[eglot] Server reports (type=1): [lib] Failed to start child {XPExpert.Project.Node, "lib"}: {:badrpc, {:EXIT, {{:badmatch, {:error, :erofs}}, [{XPForge.Project, :ensure_workspace_directory, 1, [file: ~c"lib/forge/project.ex", line: 241]}, {XPForge.Project, :ensure_workspace, 1, [file: ~c"lib/forge/project.ex", line: 224]}, {XPEngine.Bootstrap, :init, 5, []}]}}}

This can be reproduced as follows. Place the text editor cursor on something like Application.spec(:myapp, :vsn), then have the LSP server perform a textDocument/definition (in Emacs: M-x xref-find-definitions), i.e., switch current buffer to the implementation code, in this case Application.spec/2 in the application.ex file, which belongs to Elixir. I guess the error may be related to the fact that the file is immutable due to Guix System specifics. In my case it is /gnu/store/1i5wvfhr3k39aldksjv42rl4w2kpa76d-elixir-1.19.5-src/source/lib/elixir/lib/application.ex, and everything at /gnu/... is read-only for a common user.

[katafrakt]

I think your guess is correct. The code fails on attempt to create an .expert directory, probably in /gnu/store/1i5wvfhr3k39aldksjv42rl4w2kpa76d-elixir-1.19.5-src/source/lib/elixir/lib/, which - as you say - is read-only. Good news is that it should not affect LSP for your main application code in any way.

Perhaps Expert could handle this situation and log a message like "Cannot initialize Engine for /this/path, because the filesystem is readonly" and gracefully quit.