Libraries, versions, API changes, and Dub

[Mike Parker]

On Thursday, 10 January 2019 at 05:44:22 UTC, Russel Winder wrote:
> It appears that libdvbv5 has undergone an (unnoticed by me till 
> just now) version change. This raises a general question for 
> creators of D bindings.
>
> libdvbv5 has versions 1.12.x, 1.14.x, 1.16.x, etc, following 
> the "odd is internal, even is released" minor version number 
> strategy. It seems wrong somehow to follow that numbering for 
> the D binding; the binding needs to have a separate evolution. 
> However the binding has to allow the user to choose the 
> major.minor number of the underlying library they have – though 
> that should perhaps be done automatically using the pkg-config 
> system.
>
> Has anyone had previous experience of this situation and can 
> give advice/direction so I don't have to build a solution from 
> first principles?

Use version conditions for the different library versions to set 
up compile-time versions you can static if on:

```
enum DVBVSupport {
     v112  = 112,
     v114  = 114,
     v116  = 116,
}

version(DVBV_114) {
     enum dvbvSupport = DVBVSupport.v114;
}
else version(DVBV_116) {
     enum dvbvSupport = DVBVSupport.v116;
}
else enum dvbvSupport = DVBVSupport.v114;

// Declarations supported in 1.12
...

static if(dvbvSupport >= DVBVSupport.v114) {
...
}

static if(dvbvSupport >= DVBVSupport.v116) {
...
}
```

This is how I handle it in the BindBC libraries, to which I'm 
porting all the active bindings from the DerelictOrg group (where 
I handled it with different git branches, which is a horribly 
confusing and inefficient way to go about it):

https://github.com/BindBC

The only drawback to it right now is that static if isn't 
supported inside enum declarations, so you'll wind up with 
multiple declarations of the enum, as I did with SDL_EventType 
here:

https://github.com/BindBC/bindbc-sdl/blob/master/source/bindbc/sdl/bind/sdlevents.d#L25

static if *is* supported in class & struct delcarations, though, 
and you can see it used in that same file in some of the event 
types, like SDL_MouseButtonEvent and SDL_MouseWheelEvent:

https://github.com/BindBC/bindbc-sdl/blob/master/source/bindbc/sdl/bind/sdlevents.d#L347