[jira] [Created] (MESOS-7124) Replaced monadic type get() functions with operator*

["Benjamin Bannier (JIRA)" <ji...@apache.org>]

Benjamin Bannier created MESOS-7124:
---------------------------------------

             Summary: Replaced monadic type get() functions with operator*
                 Key: MESOS-7124
                 URL: https://issues.apache.org/jira/browse/MESOS-7124
             Project: Mesos
          Issue Type: Improvement
          Components: libprocess, stout
            Reporter: Benjamin Bannier


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.,
{code}
m.get().fun();
{code}
instead of
{code}
m->fun();
{code}

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,
{code}
void f(const T&);
    
Try<T> m = ..;

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

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.,
{code}
m->fun();
{code}
appears more natural than
{code}
(*m).fun();
{code}
    
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}}.



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