feat(linter) eslint-plugin-unicorn: prefer code point (#1167)

crates/oxc_linter/src/rules.rs

@@ -153,6 +153,7 @@ mod unicorn {
     pub mod no_thenable;
     pub mod no_unnecessary_await;
     pub mod prefer_array_flat_map;
+    pub mod prefer_code_point;
     pub mod prefer_date_now;
     pub mod prefer_logical_operator_over_ternary;
     pub mod prefer_query_selector;
@@ -283,6 +284,7 @@ oxc_macros::declare_all_lint_rules! {
     unicorn::no_thenable,
     unicorn::no_unnecessary_await,
     unicorn::prefer_array_flat_map,
+    unicorn::prefer_code_point,
     unicorn::prefer_date_now,
     unicorn::prefer_logical_operator_over_ternary,
     unicorn::prefer_query_selector,

crates/oxc_linter/src/rules/unicorn/prefer_code_point.rs

@@ -0,0 +1,100 @@
+use oxc_ast::{ast::Expression, AstKind};
+use oxc_diagnostics::{
+    miette::{self, Diagnostic},
+    thiserror::{self, Error},
+};
+use oxc_macros::declare_oxc_lint;
+use oxc_span::Span;
+
+use crate::{context::LintContext, rule::Rule, AstNode};
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("eslint-plugin-unicorn(prefer-code-point): Prefer `{1}` over `{2}`")]
+#[diagnostic(severity(warning), help("Unicode is better supported in `{1}` than `{2}`"))]
+struct PreferCodePointDiagnostic(#[label] pub Span, pub &'static str, pub &'static str);
+
+#[derive(Debug, Default, Clone)]
+pub struct PreferCodePoint;
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// Prefers usage of `String.prototype.codePointAt` over `String.prototype.charCodeAt`.
+    /// Prefers usage of `String.fromCodePoint` over `String.fromCharCode`.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// Unicode is better supported in [`String#codePointAt()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/codePointAt) and [`String.fromCodePoint()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCodePoint).
+    ///
+    /// [Difference between `String.fromCodePoint()` and `String.fromCharCode()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCodePoint#compared_to_fromcharcode)
+    ///
+    /// ### Example
+    /// ```javascript
+    /// // bad
+    /// '🦄'.charCodeAt(0);
+    /// String.fromCharCode(0x1f984);
+    ///
+    /// // good
+    /// '🦄'.codePointAt(0);
+    /// String.fromCodePoint(0x1f984);
+    /// ```
+    PreferCodePoint,
+    pedantic
+);
+
+impl Rule for PreferCodePoint {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        let AstKind::CallExpression(call_expr) = node.kind() else { return };
+
+        let Expression::MemberExpression(memb_expr) = &call_expr.callee else { return };
+
+        if memb_expr.is_computed() || memb_expr.optional() || call_expr.optional {
+            return;
+        }
+
+        let (current, replacement, span) = match memb_expr.static_property_info() {
+            Some((span, "charCodeAt")) => ("charCodeAt", "codePointAt", span),
+            Some((span, "fromCharCode")) => ("fromCharCode", "fromCodePoint", span),
+            _ => return,
+        };
+
+        ctx.diagnostic(PreferCodePointDiagnostic(span, replacement, current));
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        r#""🦄".codePointAt(0)"#,
+        r#"foo.charCodeAt"#,
+        r#"new foo.charCodeAt"#,
+        r#"charCodeAt(0)"#,
+        r#"foo.charCodeAt?.(0)"#,
+        r#"foo?.charCodeAt(0)"#,
+        r#"foo[charCodeAt](0)"#,
+        r#"foo["charCodeAt"](0)"#,
+        r#"foo.notCharCodeAt(0)"#,
+        r#"String.fromCodePoint(0x1f984)"#,
+        r#"String.fromCodePoint"#,
+        r#"new String.fromCodePoint"#,
+        r#"fromCodePoint(foo)"#,
+        r#"String.fromCodePoint?.(foo)"#,
+        r#"String?.fromCodePoint(foo)"#,
+        r#"window.String.fromCodePoint(foo)"#,
+        r#"String[fromCodePoint](foo)"#,
+        r#"String["fromCodePoint"](foo)"#,
+        r#"String.notFromCodePoint(foo)"#,
+        r#"NotString.fromCodePoint(foo)"#,
+    ];
+
+    let fail = vec![
+        r#"string.charCodeAt(index)"#,
+        r#"(( (( string )).charCodeAt( ((index)), )))"#,
+        r#"String.fromCharCode( code )"#,
+        r#"(( (( String )).fromCharCode( ((code)), ) ))"#,
+    ];
+
+    Tester::new_without_config(PreferCodePoint::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/prefer_code_point.snap

@@ -0,0 +1,33 @@
+---
+source: crates/oxc_linter/src/tester.rs
+expression: prefer_code_point
+---
+  ⚠ eslint-plugin-unicorn(prefer-code-point): Prefer `codePointAt` over `charCodeAt`
+   ╭─[prefer_code_point.tsx:1:1]
+ 1 │ string.charCodeAt(index)
+   ·        ──────────
+   ╰────
+  help: Unicode is better supported in `codePointAt` than `charCodeAt`
+
+  ⚠ eslint-plugin-unicorn(prefer-code-point): Prefer `codePointAt` over `charCodeAt`
+   ╭─[prefer_code_point.tsx:1:1]
+ 1 │ (( (( string )).charCodeAt( ((index)), )))
+   ·                 ──────────
+   ╰────
+  help: Unicode is better supported in `codePointAt` than `charCodeAt`
+
+  ⚠ eslint-plugin-unicorn(prefer-code-point): Prefer `fromCodePoint` over `fromCharCode`
+   ╭─[prefer_code_point.tsx:1:1]
+ 1 │ String.fromCharCode( code )
+   ·        ────────────
+   ╰────
+  help: Unicode is better supported in `fromCodePoint` than `fromCharCode`
+
+  ⚠ eslint-plugin-unicorn(prefer-code-point): Prefer `fromCodePoint` over `fromCharCode`
+   ╭─[prefer_code_point.tsx:1:1]
+ 1 │ (( (( String )).fromCharCode( ((code)), ) ))
+   ·                 ────────────
+   ╰────
+  help: Unicode is better supported in `fromCodePoint` than `fromCharCode`
+
+