oxc-project/oxc · error

Missing lang attribute.

Error message

Missing lang attribute.

What it means

Raised by the jsx-a11y/html-has-lang rule when a JSX <html> element has no lang attribute. Screen readers use the lang attribute to determine pronunciation and translation of content; without it the document language is unknown to assistive technology.

Source

Thrown at crates/oxc_linter/src/rules/jsx_a11y/html_has_lang.rs:17

use oxc_ast::{
    AstKind,
    ast::{JSXAttributeItem, JSXAttributeValue, JSXExpression},
};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};

use crate::{
    AstNode,
    context::LintContext,
    rule::Rule,
    utils::{get_element_type, get_prop_value, has_jsx_prop_ignore_case},
};

fn missing_lang_prop(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Missing lang attribute.")
        .with_help("Add a `lang` attribute to the `html` element whose value represents the primary language of document.")
        .with_label(span)
}

fn missing_lang_value(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Missing value for `lang` attribute")
        .with_help("Must have meaningful value for `lang` prop.")
        .with_label(span)
}

#[derive(Debug, Default, Clone)]
pub struct HtmlHasLang;

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Ensures that every HTML document has a lang attribute.
    ///

View on GitHub (pinned to e1e7af627c)

Solutions

  1. Add lang="en" (or the appropriate BCP-47 language code) to the <html> element.
  2. If rendering multiple locales, set lang dynamically from the active locale.
Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/jsx_a11y/html_has_lang.rs:17 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/826664ef1678b0e5. Report an issue: GitHub.