oxc-project/oxc · error

Unexpected empty block statement surrounding arrow body.

Error message

Unexpected empty block statement surrounding arrow body.

What it means

Lint diagnostic from eslint/arrow-body-style: an arrow function body is an empty block statement. An empty block implicitly returns undefined, which reads as a mistake rather than an intentional no-op and is flagged separately from a non-empty block.

Source

Thrown at crates/oxc_linter/src/rules/eslint/arrow_body_style.rs:34

    context::LintContext,
    fixer::{RuleFix, RuleFixer},
    rule::{Rule, TupleRuleConfig},
};

fn expected_block_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Expected block statement surrounding arrow body.")
        .with_help("Surround the arrow body with braces and use a return statement.")
        .with_label(span)
}

fn unexpected_block_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Unexpected block statement surrounding arrow body.")
        .with_help("Move the returned value to be immediately after the `=>`.")
        .with_label(span)
}

fn unexpected_empty_block_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Unexpected empty block statement surrounding arrow body.")
        .with_help("Put a value of `undefined` immediately after the `=>`.")
        .with_label(span)
}

/// Diagnostic that is emitted when we don't have a specific help message to provide
fn unexpected_block_with_unknown_help_diagnostic(span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn("Unexpected block statement surrounding arrow body.").with_label(span)
}

#[derive(Debug, Default, PartialEq, Clone, Deserialize, Serialize, JsonSchema)]
#[serde(rename_all = "kebab-case")]
enum Mode {
    /// Enforces no braces where they can be omitted (default).
    #[default]
    AsNeeded,
    /// Enforces braces around the function body.
    Always,
    /// Enforces no braces around the function body (constrains arrow functions to the role of returning an expression).

View on GitHub (pinned to e1e7af627c)

Solutions

1. Return the intended value: () => { return value; }
2. Write the body as () => undefined if undefined is truly the intent
3. Add the missing implementation

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/eslint/arrow_body_style.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/ff649613573b1de9. Report an issue: GitHub.