oxc-project/oxc · error · OxcDiagnostic

Passing `{arg_str}` as the `deleteCount` argument is unneces

Error message

Passing `{arg_str}` as the `deleteCount` argument is unnecessary.

What it means

Raised by unicorn/no-unnecessary-array-splice-count when `Array#splice` is passed a deleteCount that provably deletes no elements (e.g. `0` or a value equal to the remaining length). The argument source text is interpolated; the faulting input is the redundant deleteCount argument at the labeled span.

Source

Thrown at crates/oxc_linter/src/rules/unicorn/no_unnecessary_array_splice_count.rs:17

use std::borrow::Cow;

use oxc_ast::{
    AstKind,
    ast::{Argument, Expression, MemberExpression, StaticMemberExpression},
    match_member_expression,
};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};

use crate::{
    AstNode, ast_util::is_method_call, context::LintContext, rule::Rule, utils::is_same_expression,
};

fn no_unnecessary_array_splice_count_diagnostic(span: Span, arg_str: &str) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!(
        "Passing `{arg_str}` as the `deleteCount` argument is unnecessary."
    ))
    .with_help("Omit the argument to delete all elements after the start index.")
    .with_label(span)
}

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

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Disallows passing `.length` or `Infinity` as the `deleteCount` or `skipCount` argument of `Array#splice()` or `Array#toSpliced()`.
    ///
    /// ### Why is this bad?
    ///
    /// When calling `Array#splice(start, deleteCount)` or `Array#toSpliced(start, skipCount)`,
    /// omitting the `deleteCount` or `skipCount` argument will delete or skip all elements after `start`.

View on GitHub (pinned to e1e7af627c)

Solutions

1. Omit the deleteCount argument when it removes nothing
2. Use `toSpliced()` for non-mutating edits on ES2023+ runtimes

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/unicorn/no_unnecessary_array_splice_count.rs:17 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/869aaa485e54a3eb. Report an issue: GitHub.