dbt-labs/dbt-core · error · syn::Error

`unhandled_panic` set multiple times.

Error message

`unhandled_panic` set multiple times.

What it means

The `unhandled_panic` option may be given at most once per #[tokio::main]/#[tokio::test]. set_unhandled_panic checks its stored Option and raises a syn::Error at the duplicate key if it is already set, before even validating the value.

Source

Thrown at crates/dbt-runtime-macros/src/entry.rs:183

        Ok(())
    }

    fn set_crate_name(&mut self, name: syn::Lit, span: Span) -> Result<(), syn::Error> {
        if self.crate_name.is_some() {
            return Err(syn::Error::new(span, "`crate` set multiple times."));
        }
        let name_path = parse_path(name, span, "crate")?;
        self.crate_name = Some(name_path);
        Ok(())
    }

    fn set_unhandled_panic(
        &mut self,
        unhandled_panic: syn::Lit,
        span: Span,
    ) -> Result<(), syn::Error> {
        if self.unhandled_panic.is_some() {
            return Err(syn::Error::new(
                span,
                "`unhandled_panic` set multiple times.",
            ));
        }

        let unhandled_panic = parse_string(unhandled_panic, span, "unhandled_panic")?;
        let unhandled_panic =
            UnhandledPanic::from_str(&unhandled_panic).map_err(|err| syn::Error::new(span, err))?;
        self.unhandled_panic = Some((unhandled_panic, span));
        Ok(())
    }

    fn macro_name(&self) -> &'static str {
        if self.is_test {
            "dbt_runtime::test"
        } else {
            "dbt_runtime::main"
        }

View on GitHub (pinned to 0267ce9170)

Solutions

1. Keep a single `unhandled_panic = "..."` key
2. Pick one behavior: `ignore` or `shutdown_runtime`
3. Remove the option to accept the default behavior

Example fix

// before
#[tokio::test(unhandled_panic = "ignore", unhandled_panic = "shutdown_runtime")]
async fn t() {}

// after
#[tokio::test(unhandled_panic = "shutdown_runtime")]
async fn t() {}

fn check_no_dupes(attr_src: &str, key: &str) -> Result<(), String> {
    let n = attr_src.matches(&format!("{} =", key)).count();
    if n <= 1 { Ok(()) } else { Err(format!("duplicate `{key}`")) }
}

When it happens

Trigger: #[tokio::test(flavor = "current_thread", unhandled_panic = "ignore", unhandled_panic = "shutdown_runtime")] — duplicate `unhandled_panic` key in the attribute.

Common situations: Refactoring test attributes and leaving the old value in place; generators emitting the option twice; merging two tests' attribute lines.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

• `worker_threads` set multiple times.
• `start_paused` set multiple times.
• `crate` set multiple times.
• No such runtime flavor `{s}`. The runtime flavors are `curre
• `worker_threads` may not be 0.

AI-assisted analysis of dbt-labs/dbt-core@0267ce9170 (2026-09-07). Data as JSON: /api/errors/303fcfcb18f08a6b. Report an issue: GitHub.