Only zero or one arguments to font functions are currently s

Error message

Only zero or one arguments to font functions are currently supported

What it means

Thrown by options_from_request() in the Rust next-font (Google) validator when request.arguments has more than one entry. The next/font/google loader semantics allow zero arguments (defaults) or exactly one configuration object; multiple argument objects are unsupported.

Source

Thrown at crates/next-core/src/next_font/google/options.rs:79

#[derive(Debug, PartialEq, Deserialize, TraceRawVcs, NonLocalValue, Encode, Decode)]
#[serde(rename_all = "camelCase")]
pub(super) struct Axis {
    pub tag: RcStr,
    pub min: f64,
    pub max: f64,
}

impl Eq for Axis {}

// Transforms the request fields to a struct suitable for making requests to
// Google Fonts. Similar to next/font/google's validateData:
// https://github.com/vercel/next.js/blob/28454c6ddbc310419467e5415aee26e48d079b46/packages/font/src/google/utils.ts#L22
pub(super) fn options_from_request(
    request: &NextFontRequest,
    data: &FxIndexMap<RcStr, FontDataEntry>,
) -> Result<NextFontGoogleOptions> {
    if request.arguments.len() > 1 {
        anyhow::bail!("Only zero or one arguments to font functions are currently supported")
    }
    // Invariant enforced above: either None or Some(the only item in the vec)
    let argument = request.arguments.last().cloned().unwrap_or_default();

    // `import` comes from the imported symbol in JS, which separates with _
    let font_family: RcStr = request.import.replace('_', " ").into();
    let font_data = data.get(&font_family).context("Unknown font")?;

    let requested_weights: FxIndexSet<RcStr> = argument
        .weight
        .map(|w| match w {
            OneOrManyStrings::One(one) => fxindexset![one],
            OneOrManyStrings::Many(many) => many.into_iter().collect(),
        })
        .unwrap_or_default();

    let mut styles = argument
        .style

View on GitHub (pinned to 0ae8c72462)

Solutions

Call the Google font function with at most one configuration object: `Roboto({ subsets: ['latin'] })`.
If you need multiple fonts, create separate font function calls rather than passing multiple config objects.
Regenerate/rebuild to ensure the SWC transform emits a single argument object.

Example fix

// before
const font = Roboto({ subsets: ['latin'] }, { weight: '400' })
// after
const font = Roboto({ subsets: ['latin'], weight: '400' })

Defensive patterns

Strategy: validation

Prevention

Call each Google font with zero or exactly one config object.
Use separate font calls for multiple fonts rather than multiple arguments.
Rely on the standard next/font/google API; avoid manually constructing font requests.

When it happens

Trigger: A next/font/google invocation that the request layer serialized with >1 argument object — typically a malformed macro/generated call to the font function passing multiple config objects.

Common situations: Tooling or a code generator emitting a font call with extra arguments; manually constructing the font request outside the normal loader; an edge case in the SWC transform producing duplicated argument objects.

Related errors

AI-assisted analysis of vercel/next.js@0ae8c72462 (2026-08-06). Data as JSON: /api/errors/add78ad7752969d0. Report an issue: GitHub.