rome · Conaclos · Mar 30, 2023 · Mar 28, 2023 · Mar 29, 2023
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -7,11 +7,12 @@
 ### Editors
 ### Formatter
 ### Linter
+#### New rules
+- [`noConfusingArrow`](https://docs.rome.tools/lint/rules/noConfusingArrow/)
 ### Parser
 ### VSCode
 ### JavaScript APIs
 
-
 ## 12.0.0
 
 ### CLI
@@ -130,7 +131,10 @@ details.
 a configuration file in your workspace/project. If Rome doesn't find a `rome.json` file, it won't
 emit diagnostics.
 
+<<<<<<< HEAD
 
+=======
+>>>>>>> 9abb92e (release: 12.0.0 (#4002))
 ## 11.0.0
 
 ### CLI

diff --git a/crates/rome_diagnostics_categories/src/categories.rs b/crates/rome_diagnostics_categories/src/categories.rs
@@ -99,6 +99,7 @@ define_categories! {
     "lint/nursery/noUselessCatch": "https://docs.rome.tools/lint/rules/noUselessCatch",
 "lint/nursery/noParameterAssign": "https://docs.rome.tools/lint/rules/noParameterAssign",
 "lint/nursery/noNamespace": "https://docs.rome.tools/lint/rules/noNamespace",
+"lint/nursery/noConfusingArrow": "https://docs.rome.tools/lint/rules/noConfusingArrow",
     // Insert new nursery rule here
     "lint/nursery/noRedeclare": "https://docs.rome.tools/lint/rules/noRedeclare",
     "lint/nursery/useNamespaceKeyword": "https://docs.rome.tools/lint/rules/useNamespaceKeyword",

diff --git a/crates/rome_js_analyze/src/analyzers/nursery.rs b/crates/rome_js_analyze/src/analyzers/nursery.rs
diff --git a/crates/rome_js_analyze/src/analyzers/nursery/no_confusing_arrow.rs b/crates/rome_js_analyze/src/analyzers/nursery/no_confusing_arrow.rs
@@ -0,0 +1,96 @@
+use rome_analyze::{context::RuleContext, declare_rule, Ast, Rule, RuleDiagnostic};
+use rome_console::markup;
+use rome_js_syntax::JsArrowFunctionExpression;
+
+declare_rule! {
+    /// Disallow arrow functions where they could be confused with comparisons.
+    ///
+    /// Arrow functions (`=>`) are similar in syntax to some comparison operators (`>`, `<`, `<=`, and `>=`).
+    /// This rule warns against using the arrow function syntax in places where it could be confused with a comparison operator.
+    ///
+    /// Source: https://eslint.org/docs/latest/rules/no-confusing-arrow
+    ///
+    /// ## Examples
+    ///
+    /// ### Invalid
+    ///
+    /// ```js,expect_diagnostic
+    /// var x = a => 1 ? 2 : 3;
+    /// var x = (a) => 1 ? 2 : 3;
+    /// ```
+    ///
+    /// ## Valid
+    ///
+    /// ```js
+    /// var x = a => (1 ? 2 : 3);
+    /// var x = (a) => (1 ? 2 : 3);
+    /// var x = (a) => {
+    ///     return 1 ? 2 : 3;
+    /// };
+    /// var x = a => { return 1 ? 2 : 3; };
+    /// ```
+    ///
+    pub(crate) NoConfusingArrow {
+        version: "next",
+        name: "noConfusingArrow",
+        recommended: false,
+    }
+}
+
+impl Rule for NoConfusingArrow {
+    type Query = Ast<JsArrowFunctionExpression>;
+    type State = ();
+    type Signals = Option<Self::State>;
+    type Options = ();
+
+    fn run(ctx: &RuleContext<Self>) -> Self::Signals {
+        let arrow_fn = ctx.query();
+
+        arrow_fn
+            .body()
+            .ok()?
+            .as_any_js_expression()?
+            .as_js_conditional_expression()
+            .is_some()
+            .then_some(())
+    }
+
+    fn diagnostic(ctx: &RuleContext<Self>, _state: &Self::State) -> Option<RuleDiagnostic> {
+        Some(RuleDiagnostic::new(
+            rule_category!(),
+            ctx.query().fat_arrow_token().ok()?.text_trimmed_range(),
+            markup! {
+                "Fat arrows can be confused with some comparison operators ("
+                    <Emphasis>"<"</Emphasis>", "
+                    <Emphasis>">"</Emphasis>", "
+                    <Emphasis>"<="</Emphasis>", "
+                    <Emphasis>">="</Emphasis>
+                ")."
+            },
+        ))
+    }
+
+    // Formatter is not happy with the added parenthesis at the time of commit.
+    // This should be fixed before enabling the action.
+    //fn action(ctx: &RuleContext<Self>, _state: &Self::State) -> Option<JsRuleAction> {
+    //    let body_expr = ctx.query().body().ok()?.as_any_js_expression()?.clone();
+    //
+    //    let mut mutation = ctx.root().begin();
+    //
+    //    mutation.replace_node(
+    //        body_expr.clone(),
+    //        AnyJsExpression::from(make::js_parenthesized_expression(
+    //            JsSyntaxToken::new_detached(JsSyntaxKind::L_PAREN, "(", [], []),
+    //            body_expr,
+    //            JsSyntaxToken::new_detached(JsSyntaxKind::R_PAREN, ")", [], []),
+    //        )),
+    //    );
+    //
+    //    Some(JsRuleAction {
+    //        category: ActionCategory::QuickFix,
+    //        applicability: Applicability::Always,
+    //        message: markup! { "Wrap the function body in parenthesis." }.to_owned(),
+    //        mutation,
+    //    })
+    //}
+}
diff --git a/crates/rome_js_analyze/tests/specs/nursery/noConfusingArrow/invalid.js b/crates/rome_js_analyze/tests/specs/nursery/noConfusingArrow/invalid.js
@@ -0,0 +1,2 @@
+var x = a => 1 ? 2 : 3;
+var x = (a) => 1 ? 2 : 3;
diff --git a/crates/rome_js_analyze/tests/specs/nursery/noConfusingArrow/invalid.js.snap b/crates/rome_js_analyze/tests/specs/nursery/noConfusingArrow/invalid.js.snap
@@ -0,0 +1,39 @@
+---
+source: crates/rome_js_analyze/tests/spec_tests.rs
+expression: invalid.js
+---
+# Input
+```js
+var x = a => 1 ? 2 : 3;
+var x = (a) => 1 ? 2 : 3;
+
+```
+
+# Diagnostics
+```
+invalid.js:1:11 lint/nursery/noConfusingArrow ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Fat arrows can be confused with some comparison operators (<, >, <=, >=).
+
+  > 1 │ var x = a => 1 ? 2 : 3;
+      │           ^^
+    2 │ var x = (a) => 1 ? 2 : 3;
+    3 │ 
+
+
+```
+
+```
+invalid.js:2:13 lint/nursery/noConfusingArrow ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Fat arrows can be confused with some comparison operators (<, >, <=, >=).
+
+    1 │ var x = a => 1 ? 2 : 3;
+  > 2 │ var x = (a) => 1 ? 2 : 3;
+      │             ^^
+    3 │ 
+
+
+```
+
+
diff --git a/crates/rome_js_analyze/tests/specs/nursery/noConfusingArrow/valid.js b/crates/rome_js_analyze/tests/specs/nursery/noConfusingArrow/valid.js
@@ -0,0 +1,8 @@
+/* should not generate diagnostics */
+
+var x = a => (1 ? 2 : 3);
+var x = (a) => (1 ? 2 : 3);
+var x = (a) => {
+    return 1 ? 2 : 3;
+};
+var x = a => { return 1 ? 2 : 3; };
diff --git a/crates/rome_js_analyze/tests/specs/nursery/noConfusingArrow/valid.js.snap b/crates/rome_js_analyze/tests/specs/nursery/noConfusingArrow/valid.js.snap
@@ -0,0 +1,18 @@
+---
+source: crates/rome_js_analyze/tests/spec_tests.rs
+expression: valid.js
+---
+# Input
+```js
+/* should not generate diagnostics */
+
+var x = a => (1 ? 2 : 3);
+var x = (a) => (1 ? 2 : 3);
+var x = (a) => {
+    return 1 ? 2 : 3;
+};
+var x = a => { return 1 ? 2 : 3; };
+
+```
+
+
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		var x = a => 1 ? 2 : 3;
		var x = (a) => 1 ? 2 : 3;