feat(minifier): compress foo == true into foo == 1

crates/oxc_minifier/src/peephole/minimize_conditions.rs

@@ -1,5 +1,8 @@
 use oxc_ast::ast::*;
-use oxc_ecmascript::{ToInt32, constant_evaluation::DetermineValueType};
+use oxc_ecmascript::{
+    ToInt32,
+    constant_evaluation::{ConstantEvaluation, ConstantValue, DetermineValueType},
+};
 use oxc_span::GetSpan;
 use oxc_syntax::es_target::ESTarget;
 
@@ -22,7 +25,12 @@ impl<'a> PeepholeOptimizations {
             let mut local_change = false;
             if let Some(folded_expr) = match expr {
                 Expression::UnaryExpression(e) => self.try_minimize_not(e, ctx),
-                Expression::BinaryExpression(e) => Self::try_minimize_binary(e, ctx),
+                Expression::BinaryExpression(e) => {
+                    if Self::try_compress_is_loose_boolean(e, ctx) {
+                        local_change = true;
+                    }
+                    Self::try_minimize_binary(e, ctx)
+                }
                 Expression::LogicalExpression(e) => self.minimize_logical_expression(e, ctx),
                 Expression::ConditionalExpression(logical_expr) => {
                     if self.try_fold_expr_in_boolean_context(&mut logical_expr.test, ctx) {
@@ -154,6 +162,39 @@ impl<'a> PeepholeOptimizations {
         }
     }
 
+    /// Compress `foo == true` into `foo == 1`.
+    ///
+    /// - `foo == true` => `foo == 1`
+    /// - `foo != false` => `foo != 0`
+    ///
+    /// In `IsLooselyEqual`, `true` and `false` are converted to `1` and `0` first.
+    /// <https://tc39.es/ecma262/multipage/abstract-operations.html#sec-islooselyequal>
+    fn try_compress_is_loose_boolean(e: &mut BinaryExpression<'a>, ctx: Ctx<'a, '_>) -> bool {
+        if !matches!(e.operator, BinaryOperator::Equality | BinaryOperator::Inequality) {
+            return false;
+        }
+
+        if let Some(ConstantValue::Boolean(left_bool)) = e.left.evaluate_value(&ctx) {
+            e.left = ctx.ast.expression_numeric_literal(
+                e.left.span(),
+                if left_bool { 1.0 } else { 0.0 },
+                None,
+                NumberBase::Decimal,
+            );
+            return true;
+        }
+        if let Some(ConstantValue::Boolean(right_bool)) = e.right.evaluate_value(&ctx) {
+            e.right = ctx.ast.expression_numeric_literal(
+                e.right.span(),
+                if right_bool { 1.0 } else { 0.0 },
+                None,
+                NumberBase::Decimal,
+            );
+            return true;
+        }
+        false
+    }
+
     /// Returns the identifier or the assignment target's identifier of the given expression.
     pub fn extract_id_or_assign_to_id<'b>(
         expr: &'b Expression<'a>,
@@ -1438,4 +1479,16 @@ mod test {
             run(code, None)
         );
     }
+
+    #[test]
+    fn test_compress_is_loose_boolean() {
+        test("v = x == true", "v = x == 1");
+        test("v = x != true", "v = x != 1");
+        test("v = x == false", "v = x == 0");
+        test("v = x != false", "v = x != 0");
+        test("v = x == !0", "v = x == 1");
+        test("v = x != !0", "v = x != 1");
+        test("v = x == !1", "v = x == 0");
+        test("v = x != !1", "v = x != 0");
+    }
 }

crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs

@@ -1324,9 +1324,9 @@ mod test {
 
     #[test]
     fn test_fold_true_false_comparison() {
-        test("v = x == true", "v = x == !0");
-        test("v = x == false", "v = x == !1");
-        test("v = x != true", "v = x != !0");
+        test("v = x == true", "v = x == 1");
+        test("v = x == false", "v = x == 0");
+        test("v = x != true", "v = x != 1");
         test("v = x < true", "v = x < !0");
         test("v = x <= true", "v = x <= !0");
         test("v = x > true", "v = x > !0");

tasks/minsize/minsize.snap

@@ -13,7 +13,7 @@ Original   | minified   | minified   | gzip       | gzip       | Fixture
 
 555.77 kB  | 270.84 kB  | 270.13 kB  | 88.26 kB   | 90.80 kB   | d3.js     
 
-1.01 MB    | 440.17 kB  | 458.89 kB  | 122.38 kB  | 126.71 kB  | bundle.min.js
+1.01 MB    | 440.17 kB  | 458.89 kB  | 122.37 kB  | 126.71 kB  | bundle.min.js
 
 1.25 MB    | 647.00 kB  | 646.76 kB  | 160.28 kB  | 163.73 kB  | three.js