oxc-project/oxc · error · OxcDiagnostic

Use `.{prop_name} {op_and_rhs}` when checking {prop_name} is

Error message

Use `.{prop_name} {op_and_rhs}` when checking {prop_name} is zero.

What it means

Raised by unicorn/explicit-length-check when code checks a non-zero length via a non-explicit comparison while checking for the empty case, e.g. if (arr.length === 0) else-branches should use the explicit non-zero form.

Source

Thrown at crates/oxc_linter/src/rules/unicorn/explicit_length_check.rs:34

    utils::{
        expression_uses_optional_chain, get_boolean_ancestor, is_boolean_call, is_boolean_node,
        pad_fix_with_token_boundary,
    },
};

fn non_zero(span: Span, prop_name: &str, op_and_rhs: &str, help: Option<String>) -> OxcDiagnostic {
    let mut d = OxcDiagnostic::warn(format!(
        "Use `.{prop_name} {op_and_rhs}` when checking {prop_name} is not zero."
    ))
    .with_label(span);
    if let Some(x) = help {
        d = d.with_help(x);
    }
    d
}

fn zero(span: Span, prop_name: &str, op_and_rhs: &str, help: Option<String>) -> OxcDiagnostic {
    let mut d = OxcDiagnostic::warn(format!(
        "Use `.{prop_name} {op_and_rhs}` when checking {prop_name} is zero."
    ));
    if let Some(x) = help {
        d = d.with_help(x);
    }
    d.with_label(span)
}

#[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema)]
#[serde(rename_all = "kebab-case")]
enum NonZero {
    /// Enforces non-zero to be checked with `foo.length > 0`.
    #[default]
    GreaterThan,
    /// Enforces non-zero to be checked with `foo.length !== 0`.
    NotEqual,
}

View on GitHub (pinned to e1e7af627c)

Solutions

1. Use the explicit comparison form suggested in the message, e.g. arr.length !== 0 or arr.length > 0.
2. Align the comparison operator with the configured rule mode.

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/unicorn/explicit_length_check.rs:34 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/534e44c5ecac555a. Report an issue: GitHub.