feat(linter): eslint/guard-for-in (#2746)

Rule details: https://eslint.org/docs/latest/rules/guard-for-in

---------

Co-authored-by: j.buendia <j.buendia>

crates/oxc_linter/src/rules.rs

@@ -43,6 +43,7 @@ mod eslint {
     pub mod eqeqeq;
     pub mod for_direction;
     pub mod getter_return;
+    pub mod guard_for_in;
     pub mod max_lines;
     pub mod no_array_constructor;
     pub mod no_async_promise_executor;
@@ -360,6 +361,7 @@ oxc_macros::declare_all_lint_rules! {
     eslint::eqeqeq,
     eslint::for_direction,
     eslint::getter_return,
+    eslint::guard_for_in,
     eslint::max_lines,
     eslint::no_ternary,
     eslint::no_this_before_super,

crates/oxc_linter/src/rules/eslint/guard_for_in.rs

@@ -0,0 +1,100 @@
+use oxc_ast::ast::Statement;
+use oxc_ast::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};
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("eslint(guard-for-in): Require `for-in` loops to include an `if` statement")]
+#[diagnostic(severity(warning), help("The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype."))]
+struct GuardForInDiagnostic(#[label] pub Span);
+
+#[derive(Debug, Default, Clone)]
+pub struct GuardForIn;
+
+declare_oxc_lint!(
+    /// ### What it does
+    /// This rule is aimed at preventing unexpected behavior that could arise from using a for in loop without filtering the results in the loop. As such, it will warn when for in loops do not filter their results with an if statement.
+    ///
+    /// ### Why is this bad?
+    ///
+    ///
+    /// ### Example
+    /// ```javascript
+    /// for (key in foo) {
+    //     doSomething(key);
+    // }
+    /// ```
+    GuardForIn,
+    style
+);
+
+impl Rule for GuardForIn {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        if let AstKind::ForInStatement(for_in_statement) = node.kind() {
+            match &for_in_statement.body {
+                Statement::EmptyStatement(_) | Statement::IfStatement(_) => return,
+                Statement::BlockStatement(block_body) if block_body.body.is_empty() => return,
+                Statement::BlockStatement(block_body)
+                    if block_body.body.len() == 1
+                        && matches!(block_body.body[0], Statement::IfStatement(_)) =>
+                {
+                    return
+                }
+                Statement::BlockStatement(block_body) if block_body.body.len() >= 1 => {
+                    let block_statement = &block_body.body[0];
+                    if let Statement::IfStatement(i) = block_statement {
+                        if let Statement::ContinueStatement(_) = &i.consequent {
+                            return;
+                        }
+                        if let Statement::BlockStatement(consequent_block) = &i.consequent {
+                            if consequent_block.body.len() == 1
+                                && matches!(
+                                    &consequent_block.body[0],
+                                    Statement::ContinueStatement(_)
+                                )
+                            {
+                                return;
+                            }
+                        }
+                    }
+                }
+                _ => {}
+            }
+            ctx.diagnostic(GuardForInDiagnostic(Span::new(
+                for_in_statement.span.start,
+                for_in_statement.span.end,
+            )));
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        "for (var x in o);",
+        "for (var x in o) {}",
+        "for (var x in o) if (x) f();",
+        "for (var x in o) { if (x) { f(); } }",
+        "for (var x in o) { if (x) continue; f(); }",
+        "for (var x in o) { if (x) { continue; } f(); }",
+    ];
+
+    let fail = vec![
+        "for (var x in o) { if (x) { f(); continue; } g(); }",
+        "for (var x in o) { if (x) { continue; f(); } g(); }",
+        "for (var x in o) { if (x) { f(); } g(); }",
+        "for (var x in o) { if (x) f(); g(); }",
+        "for (var x in o) { foo() }",
+        "for (var x in o) foo();",
+    ];
+
+    Tester::new(GuardForIn::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/guard_for_in.snap

@@ -0,0 +1,45 @@
+---
+source: crates/oxc_linter/src/tester.rs
+expression: guard_for_in
+---
+  ⚠ eslint(guard-for-in): Require `for-in` loops to include an `if` statement
+   ╭─[guard_for_in.tsx:1:1]
+ 1 │ for (var x in o) { if (x) { f(); continue; } g(); }
+   · ───────────────────────────────────────────────────
+   ╰────
+  help: The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype.
+
+  ⚠ eslint(guard-for-in): Require `for-in` loops to include an `if` statement
+   ╭─[guard_for_in.tsx:1:1]
+ 1 │ for (var x in o) { if (x) { continue; f(); } g(); }
+   · ───────────────────────────────────────────────────
+   ╰────
+  help: The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype.
+
+  ⚠ eslint(guard-for-in): Require `for-in` loops to include an `if` statement
+   ╭─[guard_for_in.tsx:1:1]
+ 1 │ for (var x in o) { if (x) { f(); } g(); }
+   · ─────────────────────────────────────────
+   ╰────
+  help: The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype.
+
+  ⚠ eslint(guard-for-in): Require `for-in` loops to include an `if` statement
+   ╭─[guard_for_in.tsx:1:1]
+ 1 │ for (var x in o) { if (x) f(); g(); }
+   · ─────────────────────────────────────
+   ╰────
+  help: The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype.
+
+  ⚠ eslint(guard-for-in): Require `for-in` loops to include an `if` statement
+   ╭─[guard_for_in.tsx:1:1]
+ 1 │ for (var x in o) { foo() }
+   · ──────────────────────────
+   ╰────
+  help: The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype.
+
+  ⚠ eslint(guard-for-in): Require `for-in` loops to include an `if` statement
+   ╭─[guard_for_in.tsx:1:1]
+ 1 │ for (var x in o) foo();
+   · ───────────────────────
+   ╰────
+  help: The body of a for-in should be wrapped in an if statement to filter unwanted properties from the prototype.