astral-sh/ruff · error

Flame layer to be created

Error message

Flame layer to be created

What it means

When TY_LOG_PROFILE is '1' or 'true', ty attaches a tracing_flame FlameLayer writing 'tracing.folded' relative to the current directory. FlameLayer::with_files creation failure is turned into a panic by .expect("Flame layer to be created").

Source

Thrown at crates/ty/src/logging.rs:201

        subscriber.init();
    }

    Ok(TracingGuard {
        _flame_guard: guard,
    })
}

#[expect(clippy::type_complexity)]
fn setup_profile<S>() -> (
    Option<tracing_flame::FlameLayer<S, BufWriter<File>>>,
    Option<tracing_flame::FlushGuard<BufWriter<File>>>,
)
where
    S: Subscriber + for<'span> LookupSpan<'span>,
{
    if let Ok("1" | "true") = std::env::var(EnvVars::TY_LOG_PROFILE).as_deref() {
        let (layer, guard) = tracing_flame::FlameLayer::with_file("tracing.folded")
            .expect("Flame layer to be created");
        (Some(layer), Some(guard))
    } else {
        (None, None)
    }
}

pub(crate) struct TracingGuard {
    _flame_guard: Option<tracing_flame::FlushGuard<BufWriter<File>>>,
}

struct TyFormat {
    display_timestamp: bool,
    display_level: bool,
    show_spans: bool,
}

/// See <https://docs.rs/tracing-subscriber/0.3.18/src/tracing_subscriber/fmt/format/mod.rs.html#1026-1156>
impl<S, N> FormatEvent<S, N> for TyFormat

View on GitHub (pinned to d1087a4b9e)

Solutions

1. Unset TY_LOG_PROFILE if flame profiling was not intended
2. Run ty from a writable directory so tracing.folded can be created
3. Fix filesystem permissions or mount a writable path in containers before enabling profiling

Example fix

# before (read-only cwd -> panic on startup)
TY_LOG_PROFILE=1 ty check .

# after
cd /tmp/writable && TY_LOG_PROFILE=1 ty check /src

if [[ "${TY_LOG_PROFILE:-}" == 1 || "${TY_LOG_PROFILE:-}" == true ]]; then
  [ -w . ] || { echo 'cwd not writable; unsetting TY_LOG_PROFILE'; unset TY_LOG_PROFILE; }
fi

When it happens

Trigger: Starting ty with TY_LOG_PROFILE=1 from a directory where 'tracing.folded' cannot be created: read-only filesystem, missing permissions, or a container/sandbox without a writable cwd.

Common situations: Profiling inside containers with read-only root filesystems; CI runners with restricted write access; a stray TY_LOG_PROFILE left exported in the environment.

Related errors

• `initLogging` to only be called at most once.
• `initLogging` to only be called at most once.
• extra use-def data should have been retained
• Expected a Title
• unexpected annotation type: {annotation:?}

AI-assisted analysis of astral-sh/ruff@d1087a4b9e (2026-08-20). Data as JSON: /api/errors/b83747935492b14d. Report an issue: GitHub.