oxc-project/oxc · warning · OxcDiagnostic

Key `{key}` is reserved in `{group}` group.

Error message

Key `{key}` is reserved in `{group}` group.

What it means

The underscore variant of vue/no-reserved-keys: 'Key `{key}` is reserved in `{group}` group.' Vue treats `_`-prefixed properties as internal (not proxied on the instance), so a key starting with `_` declared in a group such as `props`, `data`, `computed`, `methods` or `setup` will not be reachable as `this.key` / in the template. The message names the offending group so you know exactly where the key lives.

Source

Thrown at crates/oxc_linter/src/rules/vue/no_reserved_keys.rs:57

    "$watch",
    "$set",
    "$delete",
    "$on",
    "$once",
    "$off",
    "$emit",
    "$mount",
    "$forceUpdate",
    "$nextTick",
    "$destroy",
];

fn reserved_key_diagnostic(name: &str, span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("Key `{name}` is reserved.")).with_label(span)
}

fn starts_with_underscore_diagnostic(key: &str, group: &str, span: Span) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("Key `{key}` is reserved in `{group}` group.")).with_label(span)
}

#[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema)]
#[serde(rename_all = "camelCase", default, deny_unknown_fields)]
struct NoReservedKeysConfig {
    /// Extra reserved key names to disallow, on top of the built-in list.
    reserved: Vec<CompactStr>,
    /// Extra component option groups to inspect, on top of the built-in
    /// `props` / `computed` / `data` / `asyncData` / `methods` / `setup`.
    groups: Vec<CompactStr>,
}

#[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema)]
pub struct NoReservedKeys(Box<NoReservedKeysConfig>);

declare_oxc_lint!(
    /// ### What it does
    ///

View on GitHub (pinned to e1e7af627c)

Solutions

1. Rename the key to remove the leading underscore.
2. If the state really is private, keep it outside the proxied groups (module-scope variable or non-reactive closure state) rather than using a `_` name inside them.
3. Check the rule's `groups` config if the report names a custom group you added.
4. Re-run oxlint to confirm.

Example fix

// before
export default {
  data() {
    return { _cache: {} } // reserved in `data` group
  }
}

// after
const cache = {}; // module-scope, intentionally private
export default {
  data() {
    return { visibleCount: 0 }
  }
}

When it happens

Trigger: Declaring an `_`-prefixed key in any built-in group (`props` / `computed` / `data` / `asyncData` / `methods` / `setup`) or a group listed in the rule's `groups` config, e.g. `data() { return { _internalFlag: true } }`.

Common situations: Marking 'private' state with a `_` prefix (a common convention from other languages); library components exposing `_`-prefixed props; Nuxt `asyncData` returning underscore keys that are then unreachable in the template.

Related errors

• Key `{name}` is reserved.
• Duplicate key '{name}'. May cause name collision in script o
• `VirtualFree` failed during cleanup: {err}
• TS5081
• You should not use an arrow function to define a watcher.

AI-assisted analysis of oxc-project/oxc@e1e7af627c (2026-08-20). Data as JSON: /api/errors/6c78cd7c5eecc848. Report an issue: GitHub.