Element Get method can raise "unable to *set*" error

[marcoag]

Discussed in this PR .

Environment

SDFormat13

Description

When calling the method Get from the Element class, if the type is not matching the current value it might ultimately end up
here, where it tries to get the not-matching type on the Get call and the current value of the Param and tries to set it with the new type that was asked for in the initial Get function. I don't know what's the use case for this, maybe is an effort to correct the type because it could have been parsed with a wrong one initially?

It would be very helpful if we can figure out the use case for the code, as it will help understand the need (or not) for it and if it can be refactored to not "set" when calling Get.

Alternatively an easier/faster patch could be generalizing the message of ValueFromStringImpl to make the error less confusing. However IMHO this might be slightly incorrect as the function is actually setting something so the error it produces is currently correct.

Steps to reproduce

Run a piece of code like:

sdf::ElementPtr elem = std::make_shared<sdf::Element>();
elem->AddAttribute("key", "std::string", "test", true, errors, "");
elem->Get<int>("key");

Output

 Invalid argument. Unable to set value [test] for key[key].