feat(ecmascript): add unknown_global_side_effects to MayHaveSideEffectsContext

crates/oxc_ecmascript/src/side_effects/context.rs

@@ -29,4 +29,10 @@ pub trait MayHaveSideEffectsContext: IsGlobalReference {
 
     /// Whether property read accesses have side effects.
     fn property_read_side_effects(&self) -> PropertyReadSideEffects;
+
+    /// Whether accessing a global variable has side effects.
+    ///
+    /// Accessing a non-existing global variable will throw an error.
+    /// Global variable may be a getter that has side effects.
+    fn unknown_global_side_effects(&self) -> bool;
 }

crates/oxc_ecmascript/src/side_effects/may_have_side_effects.rs

@@ -75,7 +75,7 @@ impl MayHaveSideEffects for IdentifierReference<'_> {
             // Reading global variables may have a side effect.
             // NOTE: It should also return true when the reference might refer to a reference value created by a with statement
             // NOTE: we ignore TDZ errors
-            _ => ctx.is_global_reference(self) != Some(false),
+            _ => ctx.unknown_global_side_effects() && ctx.is_global_reference(self) != Some(false),
         }
     }
 }

crates/oxc_minifier/src/ctx.rs

@@ -37,6 +37,10 @@ impl oxc_ecmascript::side_effects::MayHaveSideEffectsContext for Ctx<'_, '_> {
     fn property_read_side_effects(&self) -> PropertyReadSideEffects {
         PropertyReadSideEffects::All
     }
+
+    fn unknown_global_side_effects(&self) -> bool {
+        true
+    }
 }
 
 impl<'a> ConstantEvaluationCtx<'a> for Ctx<'a, '_> {

crates/oxc_minifier/tests/ecmascript/may_have_side_effects.rs

@@ -12,6 +12,7 @@ struct Ctx {
     annotation: bool,
     pure_function_names: Vec<String>,
     property_read_side_effects: PropertyReadSideEffects,
+    unknown_global_side_effects: bool,
 }
 impl Default for Ctx {
     fn default() -> Self {
@@ -20,6 +21,7 @@ impl Default for Ctx {
             annotation: true,
             pure_function_names: vec![],
             property_read_side_effects: PropertyReadSideEffects::All,
+            unknown_global_side_effects: true,
         }
     }
 }
@@ -44,6 +46,10 @@ impl MayHaveSideEffectsContext for Ctx {
     fn property_read_side_effects(&self) -> PropertyReadSideEffects {
         self.property_read_side_effects
     }
+
+    fn unknown_global_side_effects(&self) -> bool {
+        self.unknown_global_side_effects
+    }
 }
 
 fn test(source_text: &str, expected: bool) {
@@ -785,6 +791,22 @@ fn test_property_read_side_effects_support() {
     // test_with_ctx("({ bar } = foo)", &none_ctx, false);
 }
 
+#[test]
+fn test_unknown_global_side_effects_support() {
+    let true_ctx = Ctx {
+        unknown_global_side_effects: true,
+        global_variable_names: vec!["foo".to_string()],
+        ..Default::default()
+    };
+    let false_ctx = Ctx {
+        unknown_global_side_effects: false,
+        global_variable_names: vec!["foo".to_string()],
+        ..Default::default()
+    };
+    test_with_ctx("foo", &true_ctx, true);
+    test_with_ctx("foo", &false_ctx, false);
+}
+
 #[test]
 fn test_object_with_to_primitive_related_properties_overridden() {
     test("+{}", false);