On Tue, Jun 27, 2017 at 12:27 AM, Nick Coghlan <ncoghlan@gmail.com> wrote:
On 26 June 2017 at 22:36, Nathaniel Smith <njs@pobox.com> wrote:
On Jun 25, 2017 12:46 AM, "Nick Coghlan" <ncoghlan@gmail.com> wrote:
On 25 June 2017 at 17:41, Nathaniel Smith <njs@pobox.com> wrote:
Maybe you're right and there are exactly 2 front-end use cases and it will turn out that the current PEP addresses them perfectly. I don't have a crystal ball; I'm making an argument from ignorance.
I'm not - we have two concrete potential consumers of the interface (pip and tox, aka "build to use" and "build to test"), and I'm designing the interface to cover their needs (i.e. out-of-tree wheel builds and actual sdists).
If we discover other use cases later, we'll worry about them then (and the easy of doing so is the nicest benefit of defining this as a Python API), but the temptation to design in hyper-flexibility now falls under YAGNI (You Ain' Gonna Need It).
My proposal also covers their needs AFAICT?
No, as you don't know in your proposal whether or not build_sdist can fail until after you've already called it, and you always need to call both `get_build_sdist_requires()` and `build_sdist()`, even if you only care about doing an out-of-tree wheel build.
Ah, this is an interesting point, thank you! I hadn't thought of that. But... it doesn't seem like a big deal in practice? If a build backend knows that it can't build an sdist from a given tree, then its get_build_sdist_requires hook (which is arbitrary code after all) can surely figure this out and return []. Or we could allow get_build_sdist_requires to also return NotImplemented (defining that to mean "building sdists is not implemented, don't even try calling build_sdist"), though maybe that's unnecessary fiddliness.
2. If you don't find the input preparation hook:
- call `get_build_sdist_requires()` - call `get_build_wheel_requires()` - install both sets of additional dependencies - call `build_sdist()` - unpack the sdist into the build directory - call `build_wheel()`
Side note: I think this is wrong -- I think you can't call get_build_wheel_requires until after you've unpacked the sdist, because that's a whole new tree that might be arbitrarily different. (In practice I guess this should never happen, but we should be clear conceptually I think.) -n -- Nathaniel J. Smith -- https://vorpus.org