feat: add curly lint rule

src/rules.rs

@@ -18,6 +18,7 @@ pub mod ban_unused_ignore;
 pub mod button_has_type;
 pub mod camelcase;
 pub mod constructor_super;
+pub mod curly;
 pub mod default_param_last;
 pub mod eqeqeq;
 pub mod explicit_function_return_type;
@@ -259,6 +260,7 @@ fn get_all_rules_raw() -> Vec<Box<dyn LintRule>> {
     Box::new(button_has_type::ButtonHasType),
     Box::new(camelcase::Camelcase),
     Box::new(constructor_super::ConstructorSuper),
+    Box::new(curly::Curly),
     Box::new(default_param_last::DefaultParamLast),
     Box::new(eqeqeq::Eqeqeq),
     Box::new(explicit_function_return_type::ExplicitFunctionReturnType),

src/rules/curly.rs

@@ -0,0 +1,234 @@
+// Copyright 2020-2025 the Deno authors. All rights reserved. MIT license.
+use super::Context;
+use super::LintRule;
+use crate::diagnostic::LintFix;
+use crate::diagnostic::LintFixChange;
+use crate::handler::Handler;
+use crate::handler::Traverse;
+use crate::tags::Tags;
+use crate::Program;
+
+use deno_ast::view::DoWhileStmt;
+use deno_ast::view::ForInStmt;
+use deno_ast::view::ForOfStmt;
+use deno_ast::view::ForStmt;
+use deno_ast::view::IfStmt;
+use deno_ast::view::NodeTrait;
+use deno_ast::view::Stmt;
+use deno_ast::view::WhileStmt;
+use deno_ast::SourceRange;
+use deno_ast::SourceRanged;
+
+#[derive(Debug)]
+pub struct Curly;
+
+const CODE: &str = "curly";
+const MESSAGE: &str =
+  "Enforce consistent brace style for all control statements";
+const HINT: &str = "Add curly braces around this statement";
+
+impl LintRule for Curly {
+  fn lint_program_with_ast_view<'view>(
+    &self,
+    context: &mut Context<'view>,
+    program: Program<'view>,
+  ) {
+    CurlyHandler.traverse(program, context);
+  }
+
+  fn code(&self) -> &'static str {
+    CODE
+  }
+
+  fn tags(&self) -> Tags {
+    &[]
+  }
+}
+
+struct CurlyHandler;
+
+impl CurlyHandler {
+  fn add_diagnostic(
+    &mut self,
+    ctx: &mut Context,
+    range: SourceRange,
+    text: &str,
+  ) {
+    ctx.add_diagnostic_with_fixes(
+      range,
+      CODE,
+      MESSAGE,
+      Some(HINT.to_string()),
+      vec![LintFix {
+        description: "Add curly braces".into(),
+        changes: vec![LintFixChange {
+          new_text: format!("{}\n  {}\n{}", "{", text, "}").into(),
+          range,
+        }],
+      }],
+    );
+  }
+
+  fn report_no_block(&mut self, ctx: &mut Context, stmt: Stmt) {
+    match stmt {
+      Stmt::Block(_) => {}
+      _ => {
+        self.add_diagnostic(ctx, stmt.range(), stmt.text());
+      }
+    }
+  }
+}
+
+impl Handler for CurlyHandler {
+  fn if_stmt(&mut self, node: &IfStmt, ctx: &mut Context) {
+    self.report_no_block(ctx, node.cons);
+
+    if let Some(alt) = node.alt {
+      self.report_no_block(ctx, alt);
+    }
+  }
+
+  fn while_stmt(&mut self, node: &WhileStmt, ctx: &mut Context) {
+    self.report_no_block(ctx, node.body);
+  }
+
+  fn do_while_stmt(&mut self, node: &DoWhileStmt, ctx: &mut Context) {
+    self.report_no_block(ctx, node.body);
+  }
+
+  fn for_stmt(&mut self, node: &ForStmt, ctx: &mut Context) {
+    self.report_no_block(ctx, node.body);
+  }
+
+  fn for_in_stmt(&mut self, node: &ForInStmt, ctx: &mut Context) {
+    self.report_no_block(ctx, node.body);
+  }
+
+  fn for_of_stmt(&mut self, node: &ForOfStmt, ctx: &mut Context) {
+    self.report_no_block(ctx, node.body);
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn valid() {
+    assert_lint_ok! {
+      Curly,
+      "if (foo) { foo; }",
+      "if (foo) { foo; } else { bar; }",
+      "while (foo) { foo; }",
+      "do { foo; } while (foo)",
+      "for (;;) { foo; }",
+      "for (const a in b) { foo; }",
+      "for (const a of b) { foo; }",
+    }
+  }
+
+  #[test]
+  fn invalid() {
+    assert_lint_err! {
+      Curly,
+      "if (foo) foo;": [
+        {
+          col: 9,
+          line: 1,
+          message: MESSAGE,
+          hint: HINT,
+          fix: (
+            "Add curly braces",
+            r#"if (foo) {
+  foo;
+}"#
+          ),
+        }
+      ],
+      "if (foo) { foo; } else bar;": [
+        {
+          col: 23,
+          line: 1,
+          message: MESSAGE,
+          hint: HINT,
+          fix: (
+            "Add curly braces",
+            r#"if (foo) { foo; } else {
+  bar;
+}"#
+          ),
+        }
+      ],
+      "while (foo) bar;": [
+        {
+          col: 12,
+          line: 1,
+          message: MESSAGE,
+          hint: HINT,
+          fix: (
+            "Add curly braces",
+            r#"while (foo) {
+  bar;
+}"#
+          ),
+        }
+      ],
+      "do bar; while (foo);": [
+        {
+          col: 3,
+          line: 1,
+          message: MESSAGE,
+          hint: HINT,
+          fix: (
+            "Add curly braces",
+            r#"do {
+  bar;
+} while (foo);"#
+          ),
+        }
+      ],
+      "for (;;) foo;": [
+        {
+          col: 9,
+          line: 1,
+          message: MESSAGE,
+          hint: HINT,
+          fix: (
+            "Add curly braces",
+            r#"for (;;) {
+  foo;
+}"#
+          ),
+        }
+      ],
+      "for (const a in b) foo;": [
+        {
+          col: 19,
+          line: 1,
+          message: MESSAGE,
+          hint: HINT,
+          fix: (
+            "Add curly braces",
+            r#"for (const a in b) {
+  foo;
+}"#
+          ),
+        }
+      ],
+      "for (const a of b) foo;": [
+        {
+          col: 19,
+          line: 1,
+          message: MESSAGE,
+          hint: HINT,
+          fix: (
+            "Add curly braces",
+            "for (const a of b) {
+  foo;
+}"
+          ),
+        }
+      ]
+    };
+  }
+}