rust-lang/rust-analyzer · error

No title could be found; this is a bug

Error message

No title could be found; this is a bug

What it means

handle_discover_msg processes messages from the workspace discovery process and needs the progress label configured in discoverWorkspaceConfig to report progress. The expect asserts a discovery message can only arrive when discovery is configured; it panics if a message arrives with no discover_workspace_config() entry, e.g. config changed after discovery started.

Source

Thrown at crates/rust-analyzer/src/main_loop.rs:1135

                                    analysis.is_proc_macro_crate(krate).is_ok_and(|it| it)
                                }),
                                _ => false,
                            }
                        }) {
                            sender.send(Task::BuildDepsHaveChanged).unwrap();
                        }
                    }
                });
            }
        }
    }

    fn handle_discover_msg(&mut self, message: DiscoverProjectMessage) {
        let title = self
            .config
            .discover_workspace_config()
            .map(|cfg| cfg.progress_label.clone())
            .expect("No title could be found; this is a bug");
        match message {
            DiscoverProjectMessage::Finished { project, buildfile } => {
                self.discover_jobs_active = self.discover_jobs_active.saturating_sub(1);
                if self.discover_jobs_active == 0 {
                    self.report_progress(&title, Progress::End, None, None, None);
                }

                let mut config = Config::clone(&*self.config);
                config.add_discovered_project_from_command(project, buildfile);
                self.update_configuration(config);
            }
            DiscoverProjectMessage::Progress { message } => {
                if self.discover_jobs_active > 0 {
                    self.report_progress(&title, Progress::Report, Some(message), None, None)
                }
            }
            DiscoverProjectMessage::Error { error, source } => {
                let message = format!("Project discovery failed: {error}");

View on GitHub (pinned to e8f7e90aa3)

Solutions

1. Restart rust-analyzer (or reload the window) after editing discoverWorkspaceConfig so stale discovery processes are killed.
2. Keep rust.analyzer.workspace.discoverConfig set as long as discovery may still be running; remove it only when no discovery is active.
3. Upgrade rust-analyzer — the handler should tolerate a missing label by ending/ignoring the stale progress report.
4. Check for orphaned discovery processes (e.g. the configured discovery command) still emitting messages and kill them.

Example fix

// before
let title = self.config.discover_workspace_config()
    .map(|cfg| cfg.progress_label.clone())
    .expect("No title could be found; this is a bug");
// after: tolerate config change mid-discovery
let Some(title) = self.config.discover_workspace_config().map(|c| c.progress_label.clone()) else { return; };

// server-side guard: only report progress while discovery is still configured
let Some(cfg) = self.config.discover_workspace_config() else { return; };
let title = cfg.progress_label.clone();

fn discovery_active(cfg: &Config) -> bool {
    cfg.discover_workspace_config().is_some()
}

When it happens

Trigger: A DiscoverProjectMessage (Started/Progress/Finished) arrives from a previously spawned discovery process after the user cleared rust.analyzer.workspace.discoverConfig (or the config was reloaded without it), so config.discover_workspace_config() returns None.

Common situations: Changing rust-analyzer settings mid-session while a project discovery run is in flight, switching workspace folders so the config lookup no longer matches, and stale discovery processes from before a settings reload.

Related errors

• Unable to get AbsPath
• received response for unknown request
• we never provide completions for excluded files
• we never provide code actions for excluded files
• unable to get FileId

AI-assisted analysis of rust-lang/rust-analyzer@e8f7e90aa3 (2026-09-03). Data as JSON: /api/errors/1bf27be32484f974. Report an issue: GitHub.