libnyanpasu/clash-nyanpasu · error · anyhow::Error

child process failed: {:?}, err: {}

Error message

child process failed: {:?}, err: {}

What it means

run_pending_migrations runs a child process (migration sidecar) and waits for it. If the child exits with a non-zero status code, this anyhow error is raised wrapping the exit status and any collected stderr/stdout error strings from the child. It signals that a migration step did not complete successfully.

Source

Thrown at backend/tauri/src/utils/init/mod.rs:93

                    errs.push_str(unsafe { std::str::from_utf8_unchecked(&buf) });
                }
                Err(e) => {
                    eprintln!("failed to read stderr: {e:?}");
                    let mut errs = errs_.lock();
                    errs.push_str(&format!("failed to read stderr: {e:?}\n"));
                    break;
                }
            }
        }
    });
    let result = child.wait();
    let _l = guard.write(); // Just for waiting the thread read all the output
    let err = errs.lock();
    result
        .map_err(|e| anyhow!("Failed to wait for child: {:?}, errs: {}", e, err))
        .and_then(|status| {
            if !status.success() {
                Err(anyhow!("child process failed: {:?}, err: {}", status, err))
            } else {
                Ok(())
            }
        })
}

/// Initialize all the config files
/// before tauri setup
pub fn init_config() -> Result<()> {
    // Check if old config dir exist and new config dir is not exist
    // let mut old_app_dir: Option<PathBuf> = None;
    // let mut app_dir: Option<PathBuf> = None;
    // crate::dialog_err!(dirs::old_app_home_dir().map(|_old_app_dir| {
    //     old_app_dir = Some(_old_app_dir);
    // }));

    // crate::dialog_err!(dirs::app_home_dir().map(|_app_dir| {
    //     app_dir = Some(_app_dir);

View on GitHub (pinned to f7dbce2997)

Solutions

1. Read the captured child output (the `errs` content) in the error message to find the migration's own failure reason
2. Verify the migration sidecar binary exists and is executable (re-run pnpm prepare:check or reinstall)
3. Check permissions and free disk space on the app data directory
4. Fix or roll back the failing migration; if caused by a code change, run the migration binary manually to reproduce
5. Retry startup once the underlying cause is fixed

Example fix

// before: opaque failure
Err(anyhow!("child process failed: {:?}, err: {}", status, err))
// after: also surface captured child output
let out = out_log.lock().join("\n");
Err(anyhow!("child process failed: {:?}, err: {}, output: {}", status, err, out))

let status = cmd.status()?;
if !status.success() { bail!("migration sidecar unavailable (exit {})", status); }

match run_pending_migrations().await {
    Ok(()) => {},
    Err(e) => {
        log::error!("migrations failed: {e:#}");
        // block startup or show recovery UI
    }
}

When it happens

Trigger: Calling run_pending_migrations when the spawned child process exits with status.success() == false, e.g. the migration binary crashes or returns a failure exit code.

Common situations: Corrupt or incompatible app data directory blocking migrations; a missing/broken sidecar binary; migration script bug; insufficient permissions on the data directory; disk full.

Related errors

• {operation} failed with status {status}
• Failed to wait for child: {:?}, errs: {}
• failed to get core version
• {stderr}
• cannot repair typed clash config before split_legacy_config

AI-assisted analysis of libnyanpasu/clash-nyanpasu@f7dbce2997 (2026-09-08). Data as JSON: /api/errors/9f4fb78d9b7c7b92. Report an issue: GitHub.