vectordotdev/vector · error

field should be named

Error message

field should be named

What it means

This panic fires in vector-config-macros when generating a JSON schema for a named-field enum variant whose field unexpectedly has no identifier (i.e. a positional/tuple field reached the named-variant code path). The macro calls `field.ident().expect("field should be named")` because by that point the variant has been classified as a struct-style (named) variant, so every field must have a name. It is a derive-time internal invariant panic, not a runtime error in user code.

Solutions

1. Check the enum variant that fails to derive: it must be a true named-field variant (`Variant { field: Type }`) for this code path
2. Inspect generate_enum_variant_schema's variant classification so tuple/newtype fields go to generate_enum_newtype_struct_variant_schema instead
3. If it is a macro bug, add an explicit shape check before calling field.ident() and emit a syn::Error with a span instead of expect()

Example fix

// before
let field_name = field.ident().expect("field should be named");
// after
let field_name = field.ident().ok_or_else(|| {
    syn::Error::new(field.span(), "expected a named field on an enum struct variant")
        .to_compile_error()
})?;

// In the macro, before calling ident():
if field.ident().is_none() {
    return syn::Error::new(field.span(), "expected named field on struct variant").to_compile_error();
}

fn is_named_field(f: &syn::Field) -> bool { f.ident.is_some() }

When it happens

Trigger: Deriving `Configurable` on an enum whose variant is dispatched to `generate_enum_struct_named_variant_schema` while a field carries no identifier — e.g. an inconsistency in the syn-derived `Variant` data or a macro-internal bug in variant classification (a tuple/newtype-style field routed into the named-field generator).

Common situations: Contributing to the vector-config derive macros and accidentally routing tuple-variant fields through the named-variant path; changing variant-shape detection logic and breaking the invariant that struct variants only contain named fields.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• must exist
• #[derive(NamedInternalEvent)] can only be used with structs
• a record with a next ID must have an event count
• a valid HTTP/1 URI is valid as an HTTP URI
• a validated HTTP endpoint is a valid `http 1` URI

AI-assisted analysis of vectordotdev/vector@bdb87aeaa4 (2026-09-16). Data as JSON: /api/errors/d948b0d93072d83b. Report an issue: GitHub.

Appendix: source

Thrown at lib/vector-config-macros/src/configurable.rs:907

    let mut names = unflattened_serialized_names(fields);
    if let Some(tag) = enclosing_tag {
        names.push(tag.to_owned());
    }
    names
}

fn generate_named_enum_field(
    field: &Field<'_>,
    sibling_keys: &[String],
) -> proc_macro2::TokenStream {
    if field.required_one_of().is_some() {
        return syn::Error::new(
            field.span(),
            "`required_one_of` is not supported on enum variant fields",
        )
        .to_compile_error();
    }
    let field_name = field.ident().expect("field should be named");
    let field_ty = field.ty();
    let field_already_contained = format!(
        "schema properties already contained entry for `{field_name}`, this should not occur"
    );
    let field_key = field.name().to_string();

    let field_schema = generate_struct_field(field, sibling_keys);

    // Fields that have no default value are inherently required.  Unlike fields on a normal
    // struct, we can't derive a default value for an individual field because `serde`
    // doesn't allow even specifying a default value for an enum overall, only structs.
    let spanned_is_optional = quote_spanned! {field.span()=>
        <#field_ty as ::vector_config::Configurable>::is_optional()
    };
    let maybe_field_required = if field.default_value().is_none() {
        Some(quote! {
        if !#spanned_is_optional {
                if !required.insert(#field_key.to_string()) {

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