feat(ecmascript): add property_read_side_effects to MayHaveSideEffectsContext

Author: sapphi-red

crates/oxc_ecmascript/src/side_effects/context.rs

@@ -2,6 +2,18 @@ use oxc_ast::ast::Expression;
 
 use crate::is_global_reference::IsGlobalReference;
 
+#[derive(Default, Clone, Copy, Debug, PartialEq, Eq)]
+pub enum PropertyReadSideEffects {
+    /// Treat all property read accesses as side effect free.
+    None,
+    /// Treat non-member property accesses as side effect free.
+    /// Member property accesses are still considered to have side effects.
+    OnlyMemberPropertyAccess,
+    /// Treat all property read accesses as possible side effects.
+    #[default]
+    All,
+}
+
 pub trait MayHaveSideEffectsContext: IsGlobalReference {
     /// Whether to respect the pure annotations.
     ///
@@ -14,4 +26,7 @@ pub trait MayHaveSideEffectsContext: IsGlobalReference {
     /// This function is called for normal function calls, new calls, and
     /// tagged template calls (`foo()`, `new Foo()`, ``foo`b` ``).
     fn is_pure_call(&self, callee: &Expression) -> bool;
+
+    /// Whether property read accesses have side effects.
+    fn property_read_side_effects(&self) -> PropertyReadSideEffects;
 }

crates/oxc_ecmascript/src/side_effects/may_have_side_effects.rs

@@ -5,7 +5,7 @@ use crate::{
     to_primitive::ToPrimitive,
 };
 
-use super::context::MayHaveSideEffectsContext;
+use super::{PropertyReadSideEffects, context::MayHaveSideEffectsContext};
 
 /// Returns true if subtree changes application state.
 ///
@@ -398,7 +398,9 @@ impl MayHaveSideEffects for MemberExpression<'_> {
         match self {
             MemberExpression::ComputedMemberExpression(e) => e.may_have_side_effects(ctx),
             MemberExpression::StaticMemberExpression(e) => e.may_have_side_effects(ctx),
-            MemberExpression::PrivateFieldExpression(_) => true,
+            MemberExpression::PrivateFieldExpression(_) => {
+                ctx.property_read_side_effects() != PropertyReadSideEffects::None
+            }
         }
     }
 }
@@ -446,6 +448,9 @@ fn property_access_may_have_side_effects(
     if object.may_have_side_effects(ctx) {
         return true;
     }
+    if ctx.property_read_side_effects() == PropertyReadSideEffects::None {
+        return false;
+    }
 
     match property {
         "length" => {
@@ -464,6 +469,9 @@ fn integer_index_property_access_may_have_side_effects(
     if object.may_have_side_effects(ctx) {
         return true;
     }
+    if ctx.property_read_side_effects() == PropertyReadSideEffects::None {
+        return false;
+    }
     match object {
         Expression::StringLiteral(s) => property as usize >= s.value.encode_utf16().count(),
         Expression::ArrayExpression(arr) => property as usize >= get_array_minimum_length(arr),

crates/oxc_ecmascript/src/side_effects/mod.rs

@@ -1,5 +1,5 @@
 mod context;
 mod may_have_side_effects;
 
-pub use context::MayHaveSideEffectsContext;
+pub use context::{MayHaveSideEffectsContext, PropertyReadSideEffects};
 pub use may_have_side_effects::MayHaveSideEffects;

crates/oxc_minifier/src/ctx.rs

@@ -4,7 +4,7 @@ use oxc_ast::{AstBuilder, ast::*};
 use oxc_ecmascript::constant_evaluation::{
     ConstantEvaluation, ConstantEvaluationCtx, ConstantValue, binary_operation_evaluate_value,
 };
-use oxc_ecmascript::side_effects::MayHaveSideEffects;
+use oxc_ecmascript::side_effects::{MayHaveSideEffects, PropertyReadSideEffects};
 use oxc_semantic::{IsGlobalReference, Scoping};
 use oxc_traverse::TraverseCtx;
 
@@ -33,6 +33,10 @@ impl oxc_ecmascript::side_effects::MayHaveSideEffectsContext for Ctx<'_, '_> {
     fn is_pure_call(&self, _callee: &Expression) -> bool {
         false
     }
+
+    fn property_read_side_effects(&self) -> PropertyReadSideEffects {
+        PropertyReadSideEffects::All
+    }
 }
 
 impl<'a> ConstantEvaluationCtx<'a> for Ctx<'a, '_> {

crates/oxc_minifier/tests/ecmascript/may_have_side_effects.rs

@@ -2,7 +2,7 @@ use oxc_allocator::Allocator;
 use oxc_ast::ast::{Expression, IdentifierReference, Statement};
 use oxc_ecmascript::{
     is_global_reference::IsGlobalReference,
-    side_effects::{MayHaveSideEffects, MayHaveSideEffectsContext},
+    side_effects::{MayHaveSideEffects, MayHaveSideEffectsContext, PropertyReadSideEffects},
 };
 use oxc_parser::Parser;
 use oxc_span::SourceType;
@@ -11,10 +11,16 @@ struct Ctx {
     global_variable_names: Vec<String>,
     annotation: bool,
     pure_function_names: Vec<String>,
+    property_read_side_effects: PropertyReadSideEffects,
 }
 impl Default for Ctx {
     fn default() -> Self {
-        Self { global_variable_names: vec![], annotation: true, pure_function_names: vec![] }
+        Self {
+            global_variable_names: vec![],
+            annotation: true,
+            pure_function_names: vec![],
+            property_read_side_effects: PropertyReadSideEffects::All,
+        }
     }
 }
 impl IsGlobalReference for Ctx {
@@ -34,6 +40,10 @@ impl MayHaveSideEffectsContext for Ctx {
             false
         }
     }
+
+    fn property_read_side_effects(&self) -> PropertyReadSideEffects {
+        self.property_read_side_effects
+    }
 }
 
 fn test(source_text: &str, expected: bool) {
@@ -750,6 +760,31 @@ fn test_is_pure_call_support() {
     test_with_ctx("bar``", &ctx, true);
 }
 
+#[test]
+fn test_property_read_side_effects_support() {
+    let all_ctx =
+        Ctx { property_read_side_effects: PropertyReadSideEffects::All, ..Default::default() };
+    let only_member_ctx = Ctx {
+        property_read_side_effects: PropertyReadSideEffects::OnlyMemberPropertyAccess,
+        ..Default::default()
+    };
+    let none_ctx =
+        Ctx { property_read_side_effects: PropertyReadSideEffects::None, ..Default::default() };
+
+    test_with_ctx("foo.bar", &all_ctx, true);
+    test_with_ctx("foo.bar", &only_member_ctx, true);
+    test_with_ctx("foo.bar", &none_ctx, false);
+    test_with_ctx("foo[0]", &none_ctx, false);
+    test_with_ctx("foo[0n]", &none_ctx, false);
+    test_with_ctx("foo[bar()]", &none_ctx, true);
+    test_with_ctx("foo.#bar", &all_ctx, true);
+    test_with_ctx("foo.#bar", &only_member_ctx, true);
+    test_with_ctx("foo.#bar", &none_ctx, false);
+    test_with_ctx("({ bar } = foo)", &all_ctx, true);
+    // test_with_ctx("({ bar } = foo)", &only_member_ctx, false);
+    // test_with_ctx("({ bar } = foo)", &none_ctx, false);
+}
+
 #[test]
 fn test_object_with_to_primitive_related_properties_overridden() {
     test("+{}", false);