vectordotdev/vector · error · syn::Error

component names must be lowercase, and contain only letters,

Error message

component names must be lowercase, and contain only letters, numbers, and underscores (e.g. "{component_name_converted}")

What it means

Compile-time validation error from `check_component_name_validity`. The macro converts the given name to the canonical form (lowercase; every non-alphanumeric ASCII char to `_`) and compares: if input != converted, the name had uppercase letters or illegal characters, and the converted form is shown as the suggested fix.

Source

Thrown at lib/vector-config-macros/src/component_name.rs:155

            ),
        ));
    }

    // Now try and parse the helper attribute as a literal string, which is the only valid form.
    // After that, make sure it's actually valid according to our naming rules.
    attr.parse_args::<LitStr>()
        .map_err(|_| {
            Error::new(
                attr.span(),
                format!(
                    "expected a string literal for the {component_type} name (i.e. `{component_type_attr}(\"...\")`)"
                ),
            )
        })
        .and_then(|component_name| {
            let component_name_str = component_name.value();
            check_component_name_validity(&component_name_str)
                .map_err(|e| Error::new(component_name.span(), e))
                .map(|()| Some(component_name_str))
        })
}

fn check_component_name_validity(component_name: &str) -> Result<(), String> {
    // In a nutshell, component names must contain only lowercase ASCII alphabetic characters, or
    // numbers, or underscores.

    if component_name.is_empty() {
        return Err("component name must be non-empty".to_string());
    }

    // We only support ASCII names, so get that out of the way.
    if !component_name.is_ascii() {
        return Err("component names may only contain ASCII characters".to_string());
    }

    // Now, we blindly try and convert the given component name into the correct format, and

View on GitHub (pinned to 3708c39b12)

Solutions

Use the exact suggestion in the error message, e.g. change `source("my-source")` to `source("my_source")`
Lowercase everything and replace hyphens/dots/spaces with underscores
Check the remaining rules: non-empty and ASCII-only

Example fix

// before
#[configurable_component(source("my-Source"))]

// after
#[configurable_component(source("my_source"))]

Defensive patterns

Strategy: validation

Validate before calling

// Optional pre-commit check: name must be lowercase snake_case ASCII
fn valid_component_name(name: &str) -> bool {
    !name.is_empty()
        && name.is_ascii()
        && name
            .chars()
            .all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == '_')
}

Prevention

Name components in snake_case from the start; the error's suggestion shows the canonical form
Avoid display names, hyphens, and CamelCase in component attributes

When it happens

Trigger: `#[configurable_component(source("my-source"))]` (hyphen), `source("MySource")` (uppercase), `source("my.source")`, `source("my source")`, or any digit/underscore-legal name broken by punctuation or capitals.

Common situations: Naming a component after a display name (`"Kafka Logs"`) or a hyphenated marketing name (`"file-source"`) instead of the snake_case identifier Vector requires for schema keys and doc slugs.

Related errors

AI-assisted analysis of vectordotdev/vector@3708c39b12 (2026-08-20). Data as JSON: /api/errors/94bbef380b2991ee. Report an issue: GitHub.