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refactor(minifier): move a != null && b -> a ?? b compression to remove_unused_expression #9468

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Merged
graphite-app merged 1 commit into from
Mar 1, 2025
Merged

refactor(minifier): move a != null && b -> a ?? b compression to remove_unused_expression #9468

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1 change: 0 additions & 1 deletion crates/oxc_minifier/src/peephole/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -166,7 +166,6 @@ impl<'a> Traverse<'a> for PeepholeOptimizations {
self.mark_current_function_as_changed();
}
}
self.substitute_exit_statement(stmt, ctx);
}

fn exit_for_statement(&mut self, stmt: &mut ForStatement<'a>, ctx: &mut TraverseCtx<'a>) {
Expand Down
96 changes: 76 additions & 20 deletions crates/oxc_minifier/src/peephole/remove_unused_expression.rs
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Expand Up @@ -79,38 +79,84 @@ impl<'a> PeepholeOptimizations {
return false;
}

// try optional chaining and nullish coalescing
if self.target >= ESTarget::ES2020 {
// "a != null && a.b()" => "a?.b()"
// "a == null || a.b()" => "a?.b()"
let LogicalExpression {
span: logical_span,
left: logical_left,
right: logical_right,
operator: logical_op,
..
} = logical_expr.as_mut();
if let Expression::BinaryExpression(binary_expr) = logical_left {
if matches!(
(logical_op, binary_expr.operator),
match (logical_op, binary_expr.operator) {
// "a != null && a.b()" => "a?.b()"
// "a == null || a.b()" => "a?.b()"
(LogicalOperator::And, BinaryOperator::Inequality)
| (LogicalOperator::Or, BinaryOperator::Equality)
) {
let name_and_id = if let Expression::Identifier(id) = &binary_expr.left {
(!ctx.is_global_reference(id) && binary_expr.right.is_null())
.then_some((id.name, &mut binary_expr.left))
} else if let Expression::Identifier(id) = &binary_expr.right {
(!ctx.is_global_reference(id) && binary_expr.left.is_null())
.then_some((id.name, &mut binary_expr.right))
} else {
None
};
if let Some((name, id)) = name_and_id {
if Self::inject_optional_chaining_if_matched(&name, id, logical_right, ctx)
{
*e = ctx.ast.move_expression(logical_right);
| (LogicalOperator::Or, BinaryOperator::Equality) => {
let name_and_id = if let Expression::Identifier(id) = &binary_expr.left {
(!ctx.is_global_reference(id) && binary_expr.right.is_null())
.then_some((id.name, &mut binary_expr.left))
} else if let Expression::Identifier(id) = &binary_expr.right {
(!ctx.is_global_reference(id) && binary_expr.left.is_null())
.then_some((id.name, &mut binary_expr.right))
} else {
None
};
if let Some((name, id)) = name_and_id {
if Self::inject_optional_chaining_if_matched(
&name,
id,
logical_right,
ctx,
) {
*e = ctx.ast.move_expression(logical_right);
self.mark_current_function_as_changed();
return false;
}
}
}
// "a == null && b" => "a ?? b"
// "a != null || b" => "a ?? b"
// "a == null && (a = b)" => "a ??= b"
// "a != null || (a = b)" => "a ??= b"
(LogicalOperator::And, BinaryOperator::Equality)
| (LogicalOperator::Or, BinaryOperator::Inequality) => {
let new_left_hand_expr = if binary_expr.right.is_null() {
Some(&mut binary_expr.left)
} else if binary_expr.left.is_null() {
Some(&mut binary_expr.right)
} else {
None
};
if let Some(new_left_hand_expr) = new_left_hand_expr {
if let Expression::AssignmentExpression(assignment_expr) = logical_right
{
if assignment_expr.operator == AssignmentOperator::Assign
&& Self::has_no_side_effect_for_evaluation_same_target(
&assignment_expr.left,
new_left_hand_expr,
ctx,
)
{
assignment_expr.span = *logical_span;
assignment_expr.operator = AssignmentOperator::LogicalNullish;
*e = ctx.ast.move_expression(logical_right);
self.mark_current_function_as_changed();
return false;
}
}

*e = ctx.ast.expression_logical(
*logical_span,
ctx.ast.move_expression(new_left_hand_expr),
LogicalOperator::Coalesce,
ctx.ast.move_expression(logical_right),
);
self.mark_current_function_as_changed();
return false;
}
}
_ => {}
}
}
}
Expand Down Expand Up @@ -735,6 +781,16 @@ mod test {
test_same("a == null || a.b()"); // a may have a getter
test("var a; null != a && a.b()", "var a; a?.b()");
test("var a; null == a || a.b()", "var a; a?.b()");

test("x == null && y", "x ?? y");
test("x != null || y", "x ?? y");
test_same("v = x == null && y");
test_same("v = x != null || y");
test("a == null && (a = b)", "a ??= b");
test("a != null || (a = b)", "a ??= b");
test_same("v = a == null && (a = b)");
test_same("v = a != null || (a = b)");
test("void (x == null && y)", "x ?? y");
}

#[test]
Expand Down
65 changes: 0 additions & 65 deletions crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -933,62 +933,6 @@ impl<'a> PeepholeOptimizations {
self.mark_current_function_as_changed();
}
}

pub fn substitute_exit_statement(&mut self, stmt: &mut Statement<'a>, ctx: Ctx<'a, '_>) {
if let Statement::ExpressionStatement(expr_stmt) = stmt {
if let Some(folded_expr) = match &mut expr_stmt.expression {
Expression::LogicalExpression(expr) => {
self.try_compress_is_null_and_to_nullish_coalescing(expr, ctx)
}
_ => None,
} {
expr_stmt.expression = folded_expr;
self.mark_current_function_as_changed();
}
}
}

/// Compress `a == null && b` to `a ?? b`
///
/// - `a == null && b` -> `a ?? b`
/// - `a != null || b` -> `a ?? b`
///
/// This can be only done when the return value is not used.
/// For example when a = 1, `a == null && b` returns `false` while `a ?? b` returns `1`.
fn try_compress_is_null_and_to_nullish_coalescing(
&self,
expr: &mut LogicalExpression<'a>,
ctx: Ctx<'a, '_>,
) -> Option<Expression<'a>> {
if self.target < ESTarget::ES2020 {
return None;
}
let target_op = match expr.operator {
LogicalOperator::And => BinaryOperator::Equality,
LogicalOperator::Or => BinaryOperator::Inequality,
LogicalOperator::Coalesce => return None,
};
let Expression::BinaryExpression(binary_expr) = &mut expr.left else {
return None;
};
if binary_expr.operator != target_op {
return None;
}
let new_left_hand_expr = if binary_expr.left.is_null() {
ctx.ast.move_expression(&mut binary_expr.right)
} else if binary_expr.right.is_null() {
ctx.ast.move_expression(&mut binary_expr.left)
} else {
return None;
};

Some(ctx.ast.expression_logical(
expr.span,
new_left_hand_expr,
LogicalOperator::Coalesce,
ctx.ast.move_expression(&mut expr.right),
))
}
}

impl<'a> LatePeepholeOptimizations {
Expand Down Expand Up @@ -1764,15 +1708,6 @@ mod test {
test_same("var a = class C { foo() { return C } }");
}

#[test]
fn test_compress_is_null_and_to_nullish_coalescing() {
test("x == null && y", "x ?? y");
test("x != null || y", "x ?? y");
test_same("v = x == null && y");
test_same("v = x != null || y");
test("void (x == null && y)", "x ?? y");
}

#[test]
fn test_compress_destructuring_assignment_target() {
test_same("var {y} = x");
Expand Down
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