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react-doctor/lang

Use a valid BCP-47 language tag on `<html lang>` (e.g. `en` / `en-US`).

Status
Active
Category
Accessibility
Assessment
Evidence-required risk
Required evidence
source code, rendered UI, accessibility audit
Default configuration
Enabled
Default severity
warn
Show technical metadata
Scope
All supported frameworks
Active when
always
Requirements
react
Tags
react-jsx-only
Priority
48 (P3)
Source
oxlint-plugin-react-doctor
Rule set
oxlint-plugin-react-doctor 0.9.3 (prompt schema 2)
On this page

Validation prompt

Confirm the detector match and collect the required evidence before deciding whether an edit is warranted.

Fires on a <html> element (including <HTML> or a component resolved to "html" via jsx-a11y polymorphic/components settings) whose lang prop is invalid: explicitly lang={undefined} or lang={null}, or a static string whose value fails BCP-47 validation: the primary subtag must match a known ISO-639 tag and every -/_-separated subtag must be alphanumeric. A dynamic value like lang={foo} is NOT flagged.

Suppress when: the primary-tag set is a partial, hand-maintained ISO-639 list, so a genuinely valid but uncommon or newer language tag absent from that set is wrongly reported.

Evidence boundary

The diagnostic proves only that the detector’s modeled source pattern matched. It does not prove runtime impact, product intent, rendered failure, or that one remediation is correct.

Establish the environment, repository policy, exceptions, and required rendered or runtime evidence before deciding the occurrence.

Record one outcome:

  • Confirmed failure: The required evidence establishes the violation.
  • Rejected: A documented exception or false-positive predicate applies.
  • Needs evidence: Named evidence can still be collected.
  • Unavailable: Required evidence cannot be collected in this run.
  • Waived with evidence: An authorized, scoped exception applies to an established failure.
  • Observation: The review records an optional tradeoff without claiming a defect.

A waiver records its scope, authority, evidence, and review condition. It is not a pass or false positive.

Default severity is registry metadata. Use the occurrence’s JSON severity after repository configuration when ordering real findings.

Fix prompt

Apply this candidate correction only after the required evidence confirms the risk.

Set lang to a valid BCP-47 / IANA language tag: <html lang="en"> or a region-qualified <html lang="en-US">, script-qualified <html lang="zh-Hans"> as needed. Never leave it as lang={undefined} or lang={null}; if the value is computed, ensure it always resolves to a real tag. If the linter rejects a tag you've confirmed is valid (e.g. a rare ISO-639 code), it's a known gap in the rule's partial tag list: suppress that line with a justifying comment. See https://oxc.rs/docs/guide/usage/linter/rules/jsx_a11y/lang

Repository-wide copy prompt

Use this repository-wide prompt only after validating each occurrence. For one occurrence, use the guidance above.

Show repository-wide prompt

Fix every confirmed react-doctor/lang diagnostic in the current repository.

Required change:

  • Set lang to a valid BCP-47 / IANA language tag: <html lang="en"> or a region-qualified <html lang="en-US">, script-qualified <html lang="zh-Hans"> as needed. Never leave it as lang={undefined} or lang={null}; if the value is computed, ensure it always resolves to a real tag. If the linter rejects a tag you've confirmed is valid (e.g. a rare ISO-639 code), it's a known gap in the rule's partial tag list: suppress that line with a justifying comment. See https://oxc.rs/docs/guide/usage/linter/rules/jsx_a11y/lang.

Validation before editing:

Fires on a <html> element (including <HTML> or a component resolved to "html" via jsx-a11y polymorphic/components settings) whose lang prop is invalid: explicitly lang={undefined} or lang={null}, or a static string whose value fails BCP-47 validation: the primary subtag must match a known ISO-639 tag and every -/_-separated subtag must be alphanumeric. A dynamic value like lang={foo} is NOT flagged.

Suppress when: the primary-tag set is a partial, hand-maintained ISO-639 list, so a genuinely valid but uncommon or newer language tag absent from that set is wrongly reported.

Constraints:

  • Make the smallest change that fixes the root cause.
  • Preserve behavior and interfaces unrelated to this diagnostic.
  • Reuse existing project components, utilities, and conventions.
  • Do not introduce render-phase side effects, render-phase state updates, or Hooks rule violations.
  • Preserve accessible names, focus order, keyboard behavior, and touch access not targeted by this rule.
  • Adapt identifiers and framework details instead of copying blindly.
  • Do not disable the rule or suppress matching code.

Assessment:

  • Record detector evidence, applicability facts, assumptions, missing evidence, and the rule class for this occurrence.
  • Return one outcome: Confirmed failure, Rejected, Needs evidence, Unavailable, Waived with evidence, or Observation.
  • A waiver records the established failure, scope, authority, evidence, and review or expiry condition. It is not a pass or false positive.

Verification:

  • Run focused tests for the changed behavior.
  • Run React Doctor and confirm this diagnostic no longer appears from changed code.
  • Run an unfiltered scan of the affected scope before claiming no cross-category regression.
  • Report the files changed and any checks you could not run.