block/buzz · error · syn::Error

expected `name`, `system`, or `fields`

Error message

expected `name`, `system`, or `fields`

What it means

The catch-all branch of #[datastore_span]'s argument parser: any key other than name, system, or fields produces 'expected `name`, `system`, or `fields`' at the offending identifier's span. It fires for typos, for unknown extras (e.g. trying target = ...), and for a `fields = ...` written with an equals sign — fields is parenthesized, so after `fields` the parser expects '(' and the '=' would be parsed as the next (unknown) key. Compile-time error.

Source

Thrown at crates/buzz-datastore-tracing/src/lib.rs:49

                    name = Some(input.parse()?);
                }
                "system" => {
                    if system.is_some() {
                        return Err(Error::new(key.span(), "duplicate `system` argument"));
                    }
                    input.parse::<Token![=]>()?;
                    system = Some(input.parse()?);
                }
                "fields" => {
                    if fields.is_some() {
                        return Err(Error::new(key.span(), "duplicate `fields` argument"));
                    }
                    let content;
                    parenthesized!(content in input);
                    fields = Some(content.parse()?);
                }
                _ => {
                    return Err(Error::new(
                        key.span(),
                        "expected `name`, `system`, or `fields`",
                    ))
                }
            }
            if !input.is_empty() {
                input.parse::<Token![,]>()?;
            }
        }

        Ok(Self {
            name: name.ok_or_else(|| Error::new(input.span(), "missing `name`"))?,
            system: system.ok_or_else(|| Error::new(input.span(), "missing `system`"))?,
            fields,
        })
    }
}

View on GitHub (pinned to eed74bde2f)

Solutions

1. Remove the unsupported key — the macro only accepts name, system, fields.
2. If you wrote `fields = (...)`, drop the equals: `fields(...)`.
3. For target/skip/level behaviour: it is already baked in (target = "buzz_datastore", skip_all, otel fields) — do not try to override.
4. Check the doc comment on datastore_span for the accepted grammar before adding new arguments.

Example fix

// before
#[datastore_span(name = "q", system = "postgresql", target = "my_target")]

// after
#[datastore_span(name = "q", system = "postgresql")] // target is always buzz_datastore

// compile-time only: `cargo check` reports the unknown key's span;
// accepted grammar: #[datastore_span(name = "...", system = "postgresql"[, fields(...)])]

When it happens

Trigger: #[datastore_span(name = "q", system = "postgresql", targets = "x")] (typo/extra key), or #[datastore_span(..., fields = (a))] (wrong syntax — fields must be fields(a)), both hitting the _ => branch at crates/buzz-datastore-tracing/src/lib.rs:48-53.

Common situations: Trying to pass tracing::instrument-style options (target, level, skip) which this macro does not accept — it fixes target=buzz_datastore and skip_all itself; muscle memory typing `fields = (...)` after name/system which do use '='.

Related errors

• duplicate `name` argument
• duplicate `system` argument
• duplicate `fields` argument
• failed to install rustls crypto provider
• connect to test DB

AI-assisted analysis of block/buzz@eed74bde2f (2026-08-20). Data as JSON: /api/errors/2a9a22ef4a651449. Report an issue: GitHub.