oxc-project/oxc · error · OxcDiagnostic

'{ident_name}' is not defined.

Error message

'{ident_name}' is not defined.

What it means

Diagnostic from react/jsx-no-undef (category: correctness). An identifier used inside JSX — a component tag (<Foo/>), or a reference inside an expression container — is not declared in scope (no import, variable, or global definition). The linter resolves the name against the module's scopes; JSX expression containers are treated like normal expressions, so undefined references there are flagged even though classic ESLint's no-undef did not look inside JSX without this rule. The rule's docs note it is largely redundant in TypeScript, where the compiler already catches undeclared variables.

Source

Thrown at crates/oxc_linter/src/rules/react/jsx_no_undef.rs:16

use oxc_ast::{
    AstKind,
    ast::{IdentifierReference, JSXElementName, JSXMemberExpression, JSXMemberExpressionObject},
};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::Span;

use crate::{
    AstNode,
    context::{ContextHost, LintContext},
    rule::Rule,
};

fn jsx_no_undef_diagnostic(ident_name: &str, span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("'{ident_name}' is not defined.")).with_label(span)
}

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

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Disallow undeclared variables in JSX.
    ///
    /// Note that this rule is generally unnecessary if you are using TypeScript, as
    /// TypeScript will catch undeclared variables for you.
    ///
    /// ### Why is this bad?
    ///
    /// It is most likely a potential ReferenceError caused by a misspelling of a variable or parameter name.
    ///
    /// ### Examples

View on GitHub (pinned to e1e7af627c)

Solutions

1. Add the missing import or declaration for the identifier
2. If the name is a legitimate global (e.g. an injected analytics object), declare it in .oxlintrc.json globals (or env) rather than silencing per line
3. If the identifier is only declared in a script type or ambient .d.ts, make sure that declaration is part of the linted project
4. In TypeScript projects where the compiler covers this, disable react/jsx-no-undef to remove duplicate reporting

Example fix

// before
function App() {
  return <Modal open={open}/>;
}

// after
import Modal from './Modal';
import { useOpen } from './state';
function App() {
  const open = useOpen();
  return <Modal open={open}/>;
}

npx oxlint -D react/jsx-no-undef src/

When it happens

Trigger: Rendering a component that was never imported: <Modal open={open}/>; referencing an undefined variable inside JSX: <div>{undefinedVar}</div>; using browser/Node globals (window is fine, but e.g. ga, dataLayer, process) that are not declared or not enabled in the lint environment/globals configuration.

Common situations: Auto-import failing when adding a component; copy-pasted JSX referencing helpers that were not copied; globals from analytics scripts or injected variables not listed in oxlint's globals/env config; projects where the rule duplicates what the TS compiler already reports.

Related errors

• Import the following Jest functions from `@jest/globals`: {g
• `button` elements must have an explicit `type` attribute.
• `button` elements must have a valid `type` attribute.
• `checked` should be used with either `onChange` or `readOnly
• Use either `checked` or `defaultChecked`, but not both.

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/4d0ea3f1a03d2df3. Report an issue: GitHub.