AssertExpectations re-evaluates MatchedBy() functions

[decibel]

It appears that AssertExpectations always re-executes every MatchedBy() function. That's a problem if the matcher isn't re-entrant. It's not hard to work around (see below), but it would be nice if the function was never evaluated a second time.

My fix:

mockAlreadyCalled := false
mock.On("bleh", mock.MatchedBy ... {
    if mockAlreadyCalled { return true }
    mockAlreadyCalled = true
...

[ernesto-jimenez]

The problem is AssertExpectations re-evaluates everything, which has other problems: mock is storing the calls internally to replicate on the assertions, which in turn means that it can have a false failure if the mocked method received a pointer and the underlying object was mutated after the call succeeded.

Last time I looked into this it was quite tricky to fix that behaviour without introducing breaking changes.

Happy to receive proposals that would be backwards-compatible, though.