oxc-project/oxc · warning · OxcDiagnostic

Nested block is redundant.

Error message

Nested block is redundant.

What it means

Diagnostic from oxlint's eslint/no-lone-blocks rule (crates/oxc_linter/src/rules/eslint/no_lone_blocks.rs:16). It reports a block nested inside another lone block ('{ { ... } }'). The outer block is redundant because it adds no scoping beyond the inner one; this is typically the residue of repeatedly removing wrappers or of copy-pasted code that carried its own braces.

Source

Thrown at crates/oxc_linter/src/rules/eslint/no_lone_blocks.rs:16

use oxc_ast::AstKind;
use oxc_ast::ast::{Declaration, VariableDeclarationKind};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};

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

fn no_lone_blocks_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Block is unnecessary.")
        .with_help("Remove the unnecessary block statement. If you need to limit variable scope, consider using a function or module instead.")
        .with_label(span)
}

fn no_nested_lone_blocks_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Nested block is redundant.")
        .with_help("Remove the redundant nested block statement.")
        .with_label(span)
}

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

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Disallows unnecessary standalone block statements.
    ///
    /// ### Why is this bad?
    ///
    /// Standalone blocks can be confusing as they do not provide any meaningful purpose when used unnecessarily.
    /// They may introduce extra nesting, reducing code readability, and can mislead readers about scope or intent.
    ///
    /// ### Examples

View on GitHub (pinned to e1e7af627c)

Solutions

1. Collapse the nesting to a single level, then remove the remaining braces if that block is itself unnecessary
2. Re-run the linter after each collapse; the rule reports one diagnostic per redundant layer
3. Re-enable editor auto-formatting (oxfmt/prettier) so stray brace levels become visible

Example fix

// before
{
  {
    doWork();
  }
}

// after
doWork();

When it happens

Trigger: A block statement whose body (after skipping other nested lone blocks) is just another block: '{ { doWork(); } }'; multiple levels of nesting are each reported.

Common situations: Automated refactors that wrapped code in blocks; debug/feature-flag wrappers ('if (FLAG) { ... }' where the if was deleted but both brace levels remained); pasting a snippet that already had braces into another braced region.

Related errors

• Block is unnecessary.
• Duplicate class member: {member_name:?}
• Duplicate conditions in if-else-if chain
• Duplicate key '{key}'
• Duplicate case label

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/4d2215ed842df674. Report an issue: GitHub.