oxc-project/oxc · warning · OxcDiagnostic

' .

Error message

{prefix} {{ after '{keyword}'{condition_if_needed}.

What it means

Oxlint's port of the ESLint rule curly. It enforces a chosen brace policy for the bodies of `if`, `else`, `for`, `while`, and `do`. The message is assembled in curly_diagnostic (crates/oxc_linter/src/rules/eslint/curly.rs:13): the prefix is Expected/Unexpected depending on the configured direction, and the suffix " condition" is appended only when the keyword is if, while, or for — so the rendered text is e.g. "Expected `{` after 'if' condition." or "Unexpected `{` after 'else'.". Modes come from the kebab-case CurlyType enum: `all` (default), `multi`, `multi-line`, `multi-or-nest`.

Solutions

1. Add braces to the flagged body (or remove them when running multi-line/multi-or-nest and the body is a single same-line statement).
2. Pick the mode that matches team convention: "all" for safety, "multi-line" for compactness.
3. Fix the whole file with the editor or oxfmt rather than statement by statement.

Example fix

// before (mode: all)
if (done) return;

// after
if (done) {
  return;
}

// .oxlintrc.json — choose the policy that matches the codebase
{
  "rules": {
    "curly": ["warn", "all"]
  }
}

When it happens

Trigger: Under `all`: any braceless body such as `if (x) return;`. Under `multi`/`multi-line`/`multi-or-nest`: multi-statement or multi-line bodies left without braces, or (multi-or-nest) a nested statement that does not sit on the same line as its keyword.

Common situations: Mixed-style files after merges or contributions; enabling `all` on code written brace-free for compactness; churn between hand-written style and formatter output.

Related errors

• A constructor name should not start with a lowercase letter.
• A function with a name starting with an uppercase letter…
• Accessor pair and should be grouped.
• All 'var' declarations must be at the top of the function…
• Assignment (=) can be replaced with operator assignment

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/cc0eefa24edfef3c. Report an issue: GitHub.

Appendix: source

Thrown at crates/oxc_linter/src/rules/eslint/curly.rs:18

use crate::fixer::{RuleFix, RuleFixer};
use crate::rule::TupleRuleConfig;
use crate::{AstNode, context::LintContext, rule::Rule};
use oxc_ast::{AstKind, ast::IfStatement, ast::Statement};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};
use schemars::JsonSchema;
use serde::{Deserialize, Serialize};
use serde_json::Value;

fn curly_diagnostic(span: Span, keyword: &str, expected: bool) -> OxcDiagnostic {
    let condition_if_needed =
        matches!(keyword, "if" | "while" | "for").then_some(" condition").unwrap_or("");
    let prefix = if expected { "Expected" } else { "Unexpected" };
    let message = format!("{prefix} {{ after '{keyword}'{condition_if_needed}.");

    OxcDiagnostic::warn(message).with_label(span)
}

/// The enforcement type for the curly rule.
#[derive(Debug, Default, Clone, PartialEq, Eq, JsonSchema, Deserialize, Serialize)]
#[serde(rename_all = "kebab-case")]
pub enum CurlyType {
    /// Require braces in all cases (default)
    #[default]
    All,
    /// Require braces only when there are multiple statements in the block
    Multi,
    /// Require braces when the block spans multiple lines
    MultiLine,
    /// Require braces when the block is nested or spans multiple lines
    MultiOrNest,
}

/// Configuration for the curly rule, specified as an array of one or two elements.

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