oxc-project/oxc · error · OxcDiagnostic

Prop '{prop_name}' requires default value to be set.

Error message

Prop '{prop_name}' requires default value to be set.

What it means

Emitted by check_object_props and check_type_signature in the vue require-default-prop rule when a prop is marked optional (or not required) in the component options or defineProps type signature but has no default value. It is a validation guard: optional props without defaults resolve to undefined, which often hides runtime bugs.

Source

Thrown at crates/oxc_linter/src/rules/vue/require_default_prop.rs:27

use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};

use crate::{
    AstNode,
    context::LintContext,
    frameworks::FrameworkOptions,
    rule::Rule,
    utils::{
        find_property, for_each_define_props_type_signature,
        is_vue_component_options_object_excluding_instance,
    },
};

const NATIVE_TYPES: [&str; 7] =
    ["String", "Number", "Boolean", "Function", "Object", "Array", "Symbol"];

fn require_default_prop_diagnostic(span: Span, prop_name: &str) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("Prop '{prop_name}' requires default value to be set."))
        .with_label(span)
}

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

declare_oxc_lint!(
    /// ### What it does
    ///
    /// Requires default value to be set for props that are not marked as
    /// `required`.
    ///
    /// ### Why is this bad?
    ///
    /// A prop that is neither required nor given a default is implicitly
    /// `undefined` when omitted. Forcing a default keeps the component's
    /// behavior explicit and avoids `undefined` leaking into the template and
    /// logic. `Boolean` props are exempt because they already default to

View on GitHub (pinned to e1e7af627c)

Solutions

1. Add a default value in the prop definition, e.g. props: { foo: { type: String, default: '' } }
2. For type-based defineProps, mark the prop required by omitting the optional '?' so a default is unnecessary
3. Use a compiler macro option like withDefaults(defineProps<...>(), { foo: '' }) for type signatures

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/vue/require_default_prop.rs:27 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/f1e0c5bd76d77fc6. Report an issue: GitHub.