[MESOS-7124] Replace monadic type get() functions with operator*

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.8.0
• Component/s: libprocess, stout
• Labels: tech-debt
• Epic Link: C++11 Upgrade
• Sprint: Resource Mgmt RI11 Sp 41
• Story Points: 3
• Assignee: Meng Zhu
• Reporter: Benjamin Bannier
• Created: 14/Feb/17 09:09
• Updated: 12/Mar/19 22:59
• Resolved: 12/Mar/19 21:15

Description

In MESOS-2757 we introduced T* operator-> for Option, Future and Try. This provided a convenient short-hand for existing member functions T& get providing identical functionality.

To finalize the work of MESOS-2757 we should replace the existing T& get() member functions with functions T& operator*.

This is desirable as having both operator-> and get in the code base at the same time lures developers into using the old-style get instead of operator-> where it is not needed, e.g.,

m.get().fun();

instead of

m->fun();

We still require the functionality of get to directly access the contained value, but the current API unnecessarily conflates two (at least from a usage perspective) unrelated aspects; in these instances, we should use an operator* instead,

void f(const T&);
    
Try<T> m = ..;

f(*m); // instead of: f(m.get());

Using operator* in these instances makes it much less likely that users would use it in instances when they wanted to call functions of the wrapped value, i.e.,

m->fun();

appears more natural than

(*m).fun();

Note that this proposed change is in line with the interface of std::optional. Also, std::shared_ptr's get is a useful function and implements an unrelated interface: it surfaces the wrapped pointer as opposed to its operator* which dereferences the wrapped pointer. Similarly, our current get also produce values, and are unrelated to std::shared_ptr's get.

Issue Links

• is related to: MESOS-2757 Add -> operator for Option<T>, Try<T>, Result<T>, Future<T>.
• relates to: MESOS-9617 Lint to catch uses of get where operator* should be used.