oxc-project/oxc · error

Missing value for `lang` attribute

Error message

Missing value for `lang` attribute

What it means

Raised by jsx-a11y/html-has-lang when the <html> element has a lang attribute whose value is missing or empty (e.g. lang="" or a lang attribute with no value). An empty language tag conveys no language information to assistive technology.

Source

Thrown at crates/oxc_linter/src/rules/jsx_a11y/html_has_lang.rs:23

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.
    ///
    /// ### Why is this bad?
    ///
    /// If the language of a webpage is not specified,
    /// the screen reader assumes the default language set by the user.
    /// Language settings become an issue for users who speak multiple languages
    /// and access website in more than one language.

View on GitHub (pinned to e1e7af627c)

Solutions

  1. Set lang to a valid non-empty BCP-47 language tag such as lang="en" or lang="pt-BR".
  2. If the value comes from a variable, ensure it is a defined string at render time.
Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/jsx_a11y/html_has_lang.rs:23 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/c87948e5b12e06c6. Report an issue: GitHub.