Currently gtest's universal value printer detects whether a value is a
container (by checking the existence of member types iterator and
const_iterator), and prints the value using gtest's built-in format if yes.
The user has no way to override this decision: even if he defines a << or
PrintTo() for the class in its namespace, gtest will still use gtest's own
printer.
The rationale behind this decision is that some environments gtest works in
define their own << for STL containers and they do a poor (compared to gtest)
job of formatting the container contents. We want to use gtest's printer even
though a << is available for the type.
This is hacky but has been working well... Until recently we found that some
classes define 'iterator' or 'const_iterator' as *private* member types. This
breaks gtest's container-detection code and results in a compiler error when
gtest tries to print such an object.
We could ask the class author to make its 'iterator' and 'const_iterator'
members public, but it may not always be a good option. It would be nice if a
*user* (as opposed to an owner) of the class could work around the problem by
providing a PrintTo() function for the class.
Therefore, I think it's useful to change gtest's printer logic to use a custom
<< or PrintTo() first if one is available, and only do the container-detection
when no << or PrintTo() is defined for the type. It may result in degraded
formatting in some cases (when an inferior << is defined by the user or
third-party for a container class), but is more principled, and gives the user
the flexibility of overriding gtest's decision if he really wants to.
Original issue reported on code.google.com by w...@google.com on 9 Mar 2011 at 7:40
Original issue reported on code.google.com by
w...@google.comon 9 Mar 2011 at 7:40