GNOME Bugzilla – Bug 633447
add annotations for override="always" and override="never"
Last modified: 2018-02-08 12:01:28 UTC
There's currently no way to have any of the vfunc flags set in a typelib. The patch I'm attaching here adds 'override: always' and 'override: never' annotations, which end up looking something like this: /** * interface_method: * override: always */ and which set the must_be_implemented and must_not_be_implemented flags in the vfunc blob in the typelib.
Created attachment 173469 [details] [review] add annotations, write vfunc flags into typelib
What are examples of real-world code where this is needed?
https://bugzilla.gnome.org/show_bug.cgi?id=625033
Without doing actual research, my instinct is that "most" vfuncs don't contain defaults. In other words, the existing GIVFuncInfoFlags are not optimal. GI_VFUNC_MUST_OVERRIDE is basically the opposite of what I'd expect, which would be GI_VFUNC_CONTAINS_DEFAULT. And what is GI_VFUNC_MUST_NOT_OVERRIDE? I don't understand that one. What would be the point of a virtual one can't override? Adding mclasen@ to CC as he stubbed out this API long ago and may still remember the rationale =)
The most important flag for us is the MUST_OVERRIDE flag. This gives us the ability to warn the user much more effectively. This is similar to C++'s pure virtual interfaces which will error out if one of the pure virtual methods isn't implemented. I think we are still doing the wrong thing in PyGI though. We need to be able to ignore this issue when overriding because in essence we are not creating final classes. I would like us to have a MUST_OVERRIDE, PURE_VIRTUAL or HAS_DEFAULT flag. The rest I don't think is particularly interesting unless there is such things as MUST_NOT_OVERRIDE.
(In reply to comment #5) Right, but I think that following the principle of safety, we should assume you have to override, and the annotation should be more of the form: /** * foo_vfunc: (contains-default) * */
Sounds reasonable. I have no idea what MUST_NOT_OVERRIDE is for either.
Created attachment 173583 [details] [review] use (contains-default) option instead I'm not sure if 'contains-default' is the right name, but I can't think of anything better right now.
people don't generally refer to interfaces as "containing" methods. I'd say "has-default". or even "has-default-implementation".
Created attachment 173936 [details] [review] add (has-default) option OK, let's try (has-default) instead.
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