fix(minifier): rotate associative operators to make it more idempotent (

#8424) another **massive** pain to debug ~~https://github.com/oxc-project/monitor-oxc/actions/runs/12717213600~~ https://github.com/oxc-project/monitor-oxc/actions/runs/12717978983/job/35455601146
oxc-project · Jan 11, 2025 · 52f88c0 · 52f88c0
1 parent a80460c
commit 52f88c0
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Showing 3 changed files with 46 additions and 2 deletions.
diff --git a/crates/oxc_minifier/src/ast_passes/peephole_minimize_conditions.rs b/crates/oxc_minifier/src/ast_passes/peephole_minimize_conditions.rs
@@ -515,7 +515,7 @@ impl<'a> PeepholeMinimizeConditions {
             }
         }
 
-        // `a ? c : b && c` -> `(a || b) && c``
+        // `a ? c : b && c` -> `(a || b) && c`
         if let Expression::LogicalExpression(logical_expr) = &mut expr.alternate {
             if logical_expr.operator == LogicalOperator::And
                 && logical_expr.right.content_eq(&expr.consequent)

diff --git a/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs b/crates/oxc_minifier/src/ast_passes/peephole_substitute_alternate_syntax.rs
@@ -149,7 +149,8 @@ impl<'a> Traverse<'a> for PeepholeSubstituteAlternateSyntax {
                 Self::try_compress_assignment_to_update_expression(e, ctx)
             }
             Expression::LogicalExpression(e) => Self::try_compress_is_null_or_undefined(e, ctx)
-                .or_else(|| self.try_compress_logical_expression_to_assignment_expression(e, ctx)),
+                .or_else(|| self.try_compress_logical_expression_to_assignment_expression(e, ctx))
+                .or_else(|| Self::try_rotate_logical_expression(e, ctx)),
             Expression::TemplateLiteral(t) => Self::try_fold_template_literal(t, ctx),
             Expression::BinaryExpression(e) => Self::try_fold_loose_equals_undefined(e, ctx)
                 .or_else(|| Self::try_compress_typeof_undefined(e, ctx)),
@@ -503,6 +504,38 @@ impl<'a, 'b> PeepholeSubstituteAlternateSyntax {
         Some(ctx.ast.move_expression(&mut expr.right))
     }
 
+    /// `a || (b || c);` -> `(a || b) || c;`
+    fn try_rotate_logical_expression(
+        expr: &mut LogicalExpression<'a>,
+        ctx: Ctx<'a, 'b>,
+    ) -> Option<Expression<'a>> {
+        let Expression::LogicalExpression(right) = &mut expr.right else { return None };
+        if right.operator != expr.operator {
+            return None;
+        }
+
+        let mut new_left = ctx.ast.expression_logical(
+            expr.span,
+            ctx.ast.move_expression(&mut expr.left),
+            expr.operator,
+            ctx.ast.move_expression(&mut right.left),
+        );
+
+        {
+            let Expression::LogicalExpression(new_left2) = &mut new_left else { unreachable!() };
+            if let Some(expr) = Self::try_rotate_logical_expression(new_left2, ctx) {
+                new_left = expr;
+            }
+        }
+
+        Some(ctx.ast.expression_logical(
+            expr.span,
+            new_left,
+            expr.operator,
+            ctx.ast.move_expression(&mut right.right),
+        ))
+    }
+
     /// Returns `true` if the assignment target and expression have no side effect for *evaluation* and points to the same reference.
     ///
     /// Evaluation here means `Evaluation` in the spec.

diff --git a/crates/oxc_minifier/tests/ast_passes/mod.rs b/crates/oxc_minifier/tests/ast_passes/mod.rs
@@ -50,6 +50,17 @@ fn integration() {
         return console.log(e || JSON.stringify(os));
     });"#,
     );
+
+    test_idempotent(
+        "if (!(foo instanceof Var) || open) {
+          arg0 = null;
+        } else if (que || !(foo && bar)) {
+          if (baz()) arg0 = null;
+        }",
+        "(!(foo instanceof Var) || open || (que || !(foo && bar)) && baz()) && (arg0 = null);",
+    );
+
+    test_same("a && (b && (c && (d && (e && (f && (g && (h && i && j && k && l && m && n && o && p && q && r && s && t && u && v && w && x && y && z)))))))");
 }
 
 #[test] // https://github.com/oxc-project/oxc/issues/4341