rust-lang/rust-analyzer · error

Unable to convert to an AbsPath

Error message

Unable to convert to an AbsPath

What it means

This panic occurs in rust-analyzer's workspace fetching when a build-file path reported by a project-discovery provider cannot be converted into an AbsPathBuf. AbsPathBuf only represents absolute, canonical filesystem paths, so a relative or otherwise invalid path makes try_from fail and the expect panics. It indicates the build system produced a build_file path that is not absolute.

Source

Thrown at crates/rust-analyzer/src/reload.rs:324

                        sender
                            .send(Task::FetchWorkspace(ProjectWorkspaceProgress::Report(msg)))
                            .unwrap()
                    }
                };

                sender.send(Task::FetchWorkspace(ProjectWorkspaceProgress::Begin)).unwrap();

                if let (Some(_command), Some(path)) = (&discover_command, &path) {
                    let build = linked_projects.iter().find_map(|project| match project {
                        LinkedProject::InlineProjectJson(it) => it.crate_by_buildfile(path),
                        _ => None,
                    });

                    if let Some(build) = build
                        && is_quiescent
                    {
                        let path = AbsPathBuf::try_from(build.build_file)
                            .expect("Unable to convert to an AbsPath");
                        let arg = DiscoverProjectParam::Buildfile(path);
                        sender.send(Task::DiscoverLinkedProjects(arg)).unwrap();
                    }
                }

                let mut workspaces: Vec<_> = linked_projects
                    .iter()
                    .map(|project| match project {
                        LinkedProject::ProjectManifest(manifest) => {
                            debug!(path = %manifest, "loading project from manifest");

                            project_model::ProjectWorkspace::load(
                                manifest.clone(),
                                &cargo_config,
                                &progress,
                            )
                        }
                        LinkedProject::InlineProjectJson(it) => {

View on GitHub (pinned to e8f7e90aa3)

Solutions

1. Find which discovery provider produced the offending build_file and make it emit an absolute path (canonicalize before reporting).
2. Check rust-analyzer's project-discovery configuration (rust-analyzer.linkedProjects / workspace layout) for paths specified relatively; convert them to absolute paths.
3. Update rust-analyzer to the latest version in case the provider was fixed to canonicalize build-file paths.
4. Report a bug with the workspace layout if the build system legitimately emits relative build_file paths.

Example fix

// before (provider emits relative path)
build.build_file = "target/build-file.json";
// after
build.build_file = std::path::absolute("target/build-file.json").unwrap().into();

fn ensure_absolute(p: &str) -> Option<AbsPathBuf> {
    let pb = std::path::PathBuf::from(p);
    if pb.is_absolute() { AbsPathBuf::try_from(pb).ok() } else {
        std::path::absolute(p).ok()?.try_into().ok()
    }
}

fn is_absolute_buildfile(p: &str) -> bool { std::path::Path::new(p).is_absolute() }

When it happens

Trigger: A workspace-discovery provider (e.g. cargo/JSON project discovery via DiscoverProjectParam::Buildfile) returns a build.build_file that is a relative path or empty/non-UTF8 path, so AbsPathBuf::try_from fails during fetch_workspaces while dispatching linked-project discovery.

Common situations: Custom or third-party build-system discovery emitting relative buildfile paths; running rust-analyzer in environments where the tool that generates build files misreports locations; rust-analyzer config pointing discovery at a project whose build-file path is computed relative to the workspace root.

Related errors

• profiler failed to start
• A receiver has been dropped, something panicked!
• Unable to serialize data
• Unable to write data
• not a BlockExpr

AI-assisted analysis of rust-lang/rust-analyzer@e8f7e90aa3 (2026-09-03). Data as JSON: /api/errors/56b39f3b66c66710. Report an issue: GitHub.