protected bool IntroduceVariableFor(JsExpression expression, int limit = 2)
{
if (expression is JsIdentifierExpression)
{
return(false);
}
if (expression is JsSymbolicParameter symbol)
{
return(false);
}
if (limit > 0 && (expression is JsMemberAccessExpression memberAccess ||
expression is JsInvocationExpression invocation && invocation.Arguments.Count == 0 && invocation.HasAnnotation <ObservableUnwrapInvocationAnnotation>()))
{
return(IntroduceVariableFor(expression.GetChildByRole(JsTreeRoles.TargetExpression), limit - 1));
}
return(true);
}
protected void ProcessTargetedExpression(JsExpression expression, JsExpression defaultValue)
{
var target = expression.GetChildByRole(JsTreeRoles.TargetExpression);
if (target.HasAnnotation <MayBeNullAnnotation>())
{
// A().B -> (A() || {}).B
if (defaultValue != null &&
(expression.HasAnnotation <MayBeNullAnnotation>() || expression.IsRootResultExpression()) &&
target.IsComplexType() &&
IntroduceVariableFor(target, 1))
{
target.ReplaceWith(_ =>
new JsBinaryExpression(target, BinaryOperatorType.ConditionalOr, defaultValue));
}
// {A().B}.MORESTUFF -> (a=A()) == null : null ? a.B.MORESTUFF
else
{
var dependentExpression = GetDependentAncestorNode(expression);
if (IntroduceVariableFor(target))
{
var variable = new JsSymbolicParameter(new JsTemporaryVariableParameter());
target.ReplaceWith(variable);
target = new JsAssignmentExpression(variable.Clone(), target);
}
else
{
target = target.Clone();
}
ReplaceOrEmit(dependentExpression, _ => {
return(CreateNullCondition(target, dependentExpression).WithAnnotation(MayBeNullAnnotation.Instance));
});
}
}
}