feat(minifier): finish implementing folding object expressions (#6586)

crates/oxc_ecmascript/src/side_effects/may_have_side_effects.rs

@@ -1,4 +1,4 @@
-use oxc_ast::ast::{Expression, ForStatementLeft, UnaryExpression};
+use oxc_ast::ast::{Expression, ForStatementLeft, PropertyKey, UnaryExpression};
 
 use super::check_for_state_change::CheckForStateChange;
 
@@ -19,3 +19,4 @@ where
 impl<'a, 'b> MayHaveSideEffects<'a, 'b> for Expression<'a> {}
 impl<'a, 'b> MayHaveSideEffects<'a, 'b> for UnaryExpression<'a> {}
 impl<'a, 'b> MayHaveSideEffects<'a, 'b> for ForStatementLeft<'a> {}
+impl<'a, 'b> MayHaveSideEffects<'a, 'b> for PropertyKey<'a> {}

crates/oxc_minifier/src/ast_passes/peephole_remove_dead_code.rs

@@ -1,6 +1,7 @@
 use oxc_allocator::Vec;
 use oxc_ast::{ast::*, Visit};
 use oxc_ecmascript::constant_evaluation::{ConstantEvaluation, IsLiteralValue};
+use oxc_ecmascript::side_effects::MayHaveSideEffects;
 use oxc_span::SPAN;
 use oxc_traverse::{Ancestor, Traverse, TraverseCtx};
 
@@ -253,8 +254,9 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
             .then(|| Some(ctx.ast.statement_empty(SPAN)))
             .unwrap_or_else(|| match &mut stmt.expression {
                 Expression::ArrayExpression(expr) => Self::try_fold_array_expression(expr, ctx),
-                // TODO: handle object expression
+                Expression::ObjectExpression(object_expr) => {
-                Expression::ObjectExpression(_object_expr) => None,
+                    Self::try_fold_object_expression(object_expr, ctx)
+                }
                 _ => None,
             })
     }
@@ -328,6 +330,97 @@ impl<'a, 'b> PeepholeRemoveDeadCode {
         ));
     }
 
+    // `{a: 1, b: 2, c: foo()}` -> `foo()`
+    fn try_fold_object_expression(
+        object_expr: &mut ObjectExpression<'a>,
+        ctx: Ctx<'a, 'b>,
+    ) -> Option<Statement<'a>> {
+        let spread_count = object_expr
+            .properties
+            .iter()
+            .filter(|prop| matches!(prop, ObjectPropertyKind::SpreadProperty(_)))
+            .count();
+
+        if spread_count == object_expr.properties.len() {
+            return None;
+        }
+
+        // if there is a spread, we can't remove the object expression
+        if spread_count > 0 {
+            let original_property_count = object_expr.properties.len();
+
+            object_expr.properties.retain(|v| match v {
+                ObjectPropertyKind::ObjectProperty(object_property) => {
+                    object_property.key.may_have_side_effects()
+                        || object_property.value.may_have_side_effects()
+                        || object_property.init.as_ref().is_some_and(
+                            oxc_ecmascript::side_effects::MayHaveSideEffects::may_have_side_effects,
+                        )
+                }
+                ObjectPropertyKind::SpreadProperty(_) => true,
+            });
+
+            if original_property_count == object_expr.properties.len() {
+                return None;
+            }
+            return Some(ctx.ast.statement_expression(
+                object_expr.span,
+                ctx.ast.expression_from_object(ctx.ast.object_expression(
+                    object_expr.span,
+                    ctx.ast.move_vec(&mut object_expr.properties),
+                    None,
+                )),
+            ));
+        }
+
+        // we can replace the object with a sequence expression
+        let mut filtered_properties = ctx.ast.vec();
+
+        for prop in object_expr.properties.iter_mut() {
+            match prop {
+                ObjectPropertyKind::ObjectProperty(object_prop) => {
+                    let key = object_prop.key.as_expression_mut();
+                    if let Some(key) = key {
+                        if key.may_have_side_effects() {
+                            let key_expr = ctx.ast.move_expression(key);
+                            filtered_properties.push(key_expr);
+                        }
+                    }
+
+                    if object_prop.value.may_have_side_effects() {
+                        let mut expr = ctx.ast.move_expression(&mut object_prop.value);
+                        filtered_properties.push(ctx.ast.move_expression(&mut expr));
+                    }
+
+                    if object_prop.init.as_ref().is_some_and(
+                        oxc_ecmascript::side_effects::MayHaveSideEffects::may_have_side_effects,
+                    ) {
+                        let mut expr = object_prop.init.take().unwrap();
+                        filtered_properties.push(ctx.ast.move_expression(&mut expr));
+                    }
+                }
+                ObjectPropertyKind::SpreadProperty(_) => {
+                    unreachable!("spread property should have been filtered out");
+                }
+            }
+        }
+
+        if filtered_properties.len() == 0 {
+            return Some(ctx.ast.statement_empty(object_expr.span));
+        } else if filtered_properties.len() == 1 {
+            return Some(
+                ctx.ast.statement_expression(object_expr.span, filtered_properties.pop().unwrap()),
+            );
+        }
+
+        return Some(ctx.ast.statement_expression(
+            object_expr.span,
+            ctx.ast.expression_from_sequence(
+                ctx.ast.sequence_expression(object_expr.span, filtered_properties),
+            ),
+        ));
+    }
+
     /// Try folding conditional expression (?:) if the condition results of the condition is known.
     fn try_fold_conditional_expression(
         expr: &mut ConditionalExpression<'a>,
@@ -460,11 +553,14 @@ mod test {
     fn test_object_literal() {
         fold("({})", "");
         fold("({a:1})", "");
-        // fold("({a:foo()})", "foo()");
+        fold("({a:foo()})", "foo()");
-        // fold("({'a':foo()})", "foo()");
+        fold("({'a':foo()})", "foo()");
         // Object-spread may trigger getters.
         fold_same("({...a})");
         fold_same("({...foo()})");
+
+        fold("({ [bar()]: foo() })", "bar(), foo()");
+        fold_same("({ ...baz, [bar()]: foo() })");
     }
 
     #[test]