oxc-project/oxc · error · OxcDiagnostic

Prefer `{good_encoding}` over `{bad_encoding}`.

Error message

Prefer `{good_encoding}` over `{bad_encoding}`.

What it means

Emitted by the unicorn/text-encoding-identifier-case rule at an encoding identifier (in `TextEncoder`/`TextDecoder` labels or JSX `charset`-style attributes) whose casing does not match the configured preference (lowercase by default). It fires on the identifier span purely for canonical casing consistency.

Source

Thrown at crates/oxc_linter/src/rules/unicorn/text_encoding_identifier_case.rs:21

use oxc_ast::{AstKind, ast::JSXAttributeName};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_semantic::NodeId;
use oxc_span::{GetSpan, Span};

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

fn text_encoding_identifier_case_diagnostic(
    span: Span,
    good_encoding: &str,
    bad_encoding: &str,
) -> OxcDiagnostic {
    OxcDiagnostic::warn(format!("Prefer `{good_encoding}` over `{bad_encoding}`.")).with_label(span)
}

#[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema)]
#[serde(default, rename_all = "camelCase", deny_unknown_fields)]
pub struct TextEncodingIdentifierCase {
    /// If `true`, prefer `utf-8` over `utf8`.
    with_dash: bool,
}

declare_oxc_lint!(
    /// ### What it does
    ///
    /// This rule enforces consistent casing for text encoding identifiers, specifically:
    /// - `'utf8'` instead of `'UTF-8'` or `'utf-8'` (or `'utf-8'` if `withDash` is enabled)
    /// - `'ascii'` instead of `'ASCII'`
    ///
    /// ### Why is this bad?
    ///

View on GitHub (pinned to e1e7af627c)

Solutions

1. Use the canonical casing, e.g. `'utf-8'` instead of `'UTF-8'` (or the inverse if configured)
2. The rule offers a fix that rewrites the identifier to the preferred casing

When it happens

Trigger: Thrown at crates/oxc_linter/src/rules/unicorn/text_encoding_identifier_case.rs:21 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/24d9c91050aa0b13. Report an issue: GitHub.