oxc-project/oxc · warning

Should not have duplicate prefix

Error message

Should not have duplicate prefix

What it means

Diagnostic from the shared jest/vitest `valid-title` rule (duplicate_prefix_diagnostic). It fires when the title starts with the same prefix as the function that wraps it — e.g. `test('test ...')` or `describe('describe ...')` — producing redundant report lines like 'test test something'.

Source

Thrown at crates/oxc_linter/src/rules/shared/jest_vitest/valid_title.rs:36

        JestFnKind, JestGeneralFnKind, PossibleJestNode, is_string_raw_member_expression,
        parse_general_jest_fn_call,
    },
};

fn title_must_be_string_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Title must be a string")
        .with_help("Replace your title with a string")
        .with_label(span)
}

fn empty_title_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Should not have an empty title")
        .with_help("Write a meaningful title for your test")
        .with_label(span)
}

fn duplicate_prefix_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Should not have duplicate prefix")
        .with_help("The function name already has the prefix, try to remove the duplicate prefix")
        .with_label(span)
}

fn accidental_space_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Should not have leading or trailing spaces")
        .with_help("Remove the leading or trailing spaces")
        .with_label(span)
}

fn disallowed_word_diagnostic(word: &str, span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("{word} is not allowed in test title"))
        .with_help("It is included in the `disallowedWords` of your config file, try to remove it from your title")
        .with_label(span)
}

pub fn must_match_diagnostic(message: &str, span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn(message.to_string())

View on GitHub (pinned to e1e7af627c)

Solutions

1. Drop the prefix from the title: `test('checkout completes', fn)`, `describe('utils', () => {})`.
2. In nested describes, make each level name its slice of scope instead of repeating the keyword: `describe('utils', () => { describe('formatDate', () => ...) })`.
3. Codemod a one-time cleanup with a regex lint pass if many titles are affected.

Example fix

// before
describe('describe user service', () => {
  it('it logs in', () => { /* ... */ });
});

// after
describe('user service', () => {
  it('logs in', () => { /* ... */ });
});

const dup = /\b(describe|test|it)(\.(skip|only|each))?\s*\(\s*(['"])(describe|test|it)\s/;
if (dup.test(src)) { console.error('title duplicates its function-name prefix'); process.exitCode = 1; }

When it happens

Trigger: `parse_general_jest_fn_call` yields the function kind (JestGeneralFnKind: test/it/describe and friends); when the title's first word duplicates the function name prefix (`'test foo'`, `'it foo'`, `'describe foo'`), the diagnostic fires. Examples: `describe('describe utils', () => {})`, `it('it works', fn)`, `test('test checkout', fn)`.

Common situations: Titles written by reading the call aloud ('test that...'), generators that prepend the keyword, and copy-paste chains where each level re-adds describe/test.

Related errors

• {word} is not allowed in test title
• {un_prefixed_name} should match {raw_pattern}
• {un_prefixed_name} should not match {raw_pattern}
• Title must be a string
• Should not have an empty title

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/46dc1a1f0ca0d0c3. Report an issue: GitHub.