feat(linter): eslint-plugin-unicorn/no-nested-ternary

crates/oxc_linter/src/rules.rs

@@ -159,6 +159,7 @@ mod unicorn {
     pub mod no_invalid_remove_event_listener;
     pub mod no_lonely_if;
     pub mod no_negated_condition;
+    pub mod no_nested_ternary;
     pub mod no_new_array;
     pub mod no_new_buffer;
     pub mod no_object_as_default_parameter;
@@ -317,6 +318,7 @@ oxc_macros::declare_all_lint_rules! {
     unicorn::no_invalid_remove_event_listener,
     unicorn::no_lonely_if,
     unicorn::no_negated_condition,
+    unicorn::no_nested_ternary,
     unicorn::no_new_array,
     unicorn::no_new_buffer,
     unicorn::no_object_as_default_parameter,

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

@@ -0,0 +1,186 @@
+use oxc_ast::{ast::Expression, AstKind};
+use oxc_diagnostics::{
+    miette::{self, Diagnostic},
+    thiserror::Error,
+};
+use oxc_macros::declare_oxc_lint;
+use oxc_span::Span;
+
+use crate::{context::LintContext, rule::Rule, AstNode, Fix};
+
+#[derive(Debug, Error, Diagnostic)]
+enum NoNestedTernaryDiagnostic {
+    #[error("eslint-plugin-unicorn(no-nested-ternary): Unexpected nested ternary expression without parentheses.")]
+    #[diagnostic(severity(warning), help("Add parentheses around the nested ternary expression."))]
+    UnparenthesizedNestedTernary(#[label] Span),
+    #[error(
+        "eslint-plugin-unicorn(no-nested-ternary): Unexpected deeply nested ternary expression."
+    )]
+    #[diagnostic(
+        severity(warning),
+        help("Avoid nesting ternary expressions for more than one level.")
+    )]
+    DeeplyNestedTernary(#[label] Span),
+}
+
+#[derive(Debug, Default, Clone)]
+pub struct NoNestedTernary;
+
+declare_oxc_lint!(
+    /// ### What it does
+    /// This rule disallows deeply nested ternary expressions.
+    /// Nested ternary expressions that are only one level deep and wrapped in parentheses are allowed.
+    ///
+    /// ### Why is this bad?
+    /// Nesting ternary expressions can make code more difficult to understand.
+    ///
+    /// ### Example
+    /// ```javascript
+    /// // Fail
+    /// const foo = i > 5 ? i < 100 ? true : false : true;
+    /// const foo = i > 5 ? true : (i < 100 ? true : (i < 1000 ? true : false));
+    ///
+    /// // Pass
+    /// const foo = i > 5 ? (i < 100 ? true : false) : true;
+    /// const foo = i > 5 ? (i < 100 ? true : false) : (i < 100 ? true : false);
+    /// ```
+    NoNestedTernary,
+    restriction
+);
+
+impl Rule for NoNestedTernary {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        let AstKind::ConditionalExpression(cond_expr) = node.kind() else { return };
+
+        if matches!(&cond_expr.test.get_inner_expression(), Expression::ConditionalExpression(_))
+            || matches!(
+                &cond_expr.consequent.get_inner_expression(),
+                Expression::ConditionalExpression(_)
+            )
+            || matches!(
+                &cond_expr.alternate.get_inner_expression(),
+                Expression::ConditionalExpression(_)
+            )
+        {
+            return;
+        }
+
+        let mut nested_level = 0;
+        let mut current_node = node;
+        while let Some(parent_node) = ctx.nodes().parent_node(current_node.id()) {
+            match parent_node.kind() {
+                AstKind::ConditionalExpression(_) => {
+                    nested_level += 1;
+                }
+                AstKind::ParenthesizedExpression(_) => {}
+                _ => break,
+            }
+            if nested_level == 2 {
+                break;
+            }
+            current_node = parent_node;
+        }
+
+        match nested_level {
+            0 => {}
+            1 => {
+                let Some(parent_node) = ctx.nodes().parent_node(node.id()) else { unreachable!() };
+                if let AstKind::ParenthesizedExpression(_) = parent_node.kind() {
+                    return;
+                }
+                ctx.diagnostic_with_fix(
+                    NoNestedTernaryDiagnostic::UnparenthesizedNestedTernary(cond_expr.span),
+                    || {
+                        Fix::new(
+                            format!("({})", cond_expr.span.source_text(ctx.source_text())),
+                            cond_expr.span,
+                        )
+                    },
+                );
+            }
+            2 => {
+                ctx.diagnostic(NoNestedTernaryDiagnostic::DeeplyNestedTernary(cond_expr.span));
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        r"const foo = i > 5 ? true : false;",
+        r"const foo = i > 5 ? true : (i < 100 ? true : false);",
+        r"const foo = i > 5 ? (i < 100 ? true : false) : true;",
+        r"const foo = i > 5 ? (i < 100 ? true : false) : (i < 100 ? true : false);",
+        r"const foo = i > 5 ? true : (i < 100 ? FOO(i > 50 ? false : true) : false);",
+        r"foo ? doBar() : doBaz();",
+        r"var foo = bar === baz ? qux : quxx;",
+        r"
+            const pluginName = isAbsolute ?
+                pluginPath.slice(pluginPath.lastIndexOf('/') + 1) :
+                (
+                    isNamespaced ?
+                    pluginPath.split('@')[1].split('/')[1] :
+                    pluginPath
+                );
+        ",
+    ];
+
+    let fail = vec![
+        r"const foo = i > 5 ? true : (i < 100 ? true : (i < 1000 ? true : false));",
+        r"const foo = i > 5 ? true : (i < 100 ? (i > 50 ? false : true) : false);",
+        r"const foo = i > 5 ? i < 100 ? true : false : true;",
+        r"const foo = i > 5 ? i < 100 ? true : false : i < 100 ? true : false;",
+        r"const foo = i > 5 ? true : i < 100 ? true : false;",
+        r"foo ? bar : baz === qux ? quxx : foobar;",
+        r"foo ? baz === qux ? quxx : foobar : bar;",
+        r"
+        const foo = a ?
+            b :
+            (
+                c ?
+                    d :
+                    (
+                        e ?
+                            f :
+                            (g ? h : i)
+                    )
+            )
+        ",
+    ];
+
+    let fix = vec![
+        (
+            "const foo = i > 5 ? i < 100 ? true : false : true;",
+            "const foo = i > 5 ? (i < 100 ? true : false) : true;",
+            None,
+        ),
+        (
+            "const foo = i > 5 ? i < 100 ? true : false : i < 100 ? true : false;",
+            "const foo = i > 5 ? (i < 100 ? true : false) : (i < 100 ? true : false);",
+            None,
+        ),
+        (
+            "const foo = i > 5 ? true : i < 100 ? true : false;",
+            "const foo = i > 5 ? true : (i < 100 ? true : false);",
+            None,
+        ),
+        (
+            "foo ? bar : baz === qux ? quxx : foobar;",
+            "foo ? bar : (baz === qux ? quxx : foobar);",
+            None,
+        ),
+        (
+            "foo ? baz === qux ? quxx : foobar : bar;",
+            "foo ? (baz === qux ? quxx : foobar) : bar;",
+            None,
+        ),
+    ];
+
+    Tester::new_without_config(NoNestedTernary::NAME, pass, fail)
+        .expect_fix(fix)
+        .test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/no_nested_ternary.snap

@@ -0,0 +1,70 @@
+---
+source: crates/oxc_linter/src/tester.rs
+expression: no_nested_ternary
+---
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected deeply nested ternary expression.
+   ╭─[no_nested_ternary.tsx:1:1]
+ 1 │ const foo = i > 5 ? true : (i < 100 ? true : (i < 1000 ? true : false));
+   ·                                               ───────────────────────
+   ╰────
+  help: Avoid nesting ternary expressions for more than one level.
+
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected deeply nested ternary expression.
+   ╭─[no_nested_ternary.tsx:1:1]
+ 1 │ const foo = i > 5 ? true : (i < 100 ? (i > 50 ? false : true) : false);
+   ·                                        ─────────────────────
+   ╰────
+  help: Avoid nesting ternary expressions for more than one level.
+
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected nested ternary expression without parentheses.
+   ╭─[no_nested_ternary.tsx:1:1]
+ 1 │ const foo = i > 5 ? i < 100 ? true : false : true;
+   ·                     ──────────────────────
+   ╰────
+  help: Add parentheses around the nested ternary expression.
+
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected nested ternary expression without parentheses.
+   ╭─[no_nested_ternary.tsx:1:1]
+ 1 │ const foo = i > 5 ? i < 100 ? true : false : i < 100 ? true : false;
+   ·                     ──────────────────────
+   ╰────
+  help: Add parentheses around the nested ternary expression.
+
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected nested ternary expression without parentheses.
+   ╭─[no_nested_ternary.tsx:1:1]
+ 1 │ const foo = i > 5 ? i < 100 ? true : false : i < 100 ? true : false;
+   ·                                              ──────────────────────
+   ╰────
+  help: Add parentheses around the nested ternary expression.
+
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected nested ternary expression without parentheses.
+   ╭─[no_nested_ternary.tsx:1:1]
+ 1 │ const foo = i > 5 ? true : i < 100 ? true : false;
+   ·                            ──────────────────────
+   ╰────
+  help: Add parentheses around the nested ternary expression.
+
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected nested ternary expression without parentheses.
+   ╭─[no_nested_ternary.tsx:1:1]
+ 1 │ foo ? bar : baz === qux ? quxx : foobar;
+   ·             ───────────────────────────
+   ╰────
+  help: Add parentheses around the nested ternary expression.
+
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected nested ternary expression without parentheses.
+   ╭─[no_nested_ternary.tsx:1:1]
+ 1 │ foo ? baz === qux ? quxx : foobar : bar;
+   ·       ───────────────────────────
+   ╰────
+  help: Add parentheses around the nested ternary expression.
+
+  ⚠ eslint-plugin-unicorn(no-nested-ternary): Unexpected deeply nested ternary expression.
+    ╭─[no_nested_ternary.tsx:9:1]
+  9 │                             f :
+ 10 │                             (g ? h : i)
+    ·                              ─────────
+ 11 │                     )
+    ╰────
+  help: Avoid nesting ternary expressions for more than one level.
+
+