feat: build recipe yaml directly

[wolfv]

This adds some "fallback" behavior if a recipe.yaml is found but no pixi.toml next to it.

We just default to the pixi-build-rattler-build backend.

I am currently testing with:

[project]
authors = ["Wolf Vollprecht <w.vollprecht@gmail.com>"]
channels = ["conda-forge"]
description = "Add a short description here"
name = "build-recipe"
platforms = ["osx-arm64"]
version = "0.1.0"
preview = ["pixi-build"]


[package]

[build-system]
dependencies = []
# note this is unused garbage but currently necessary
build-backend = "bla"
channels = [
    "https://prefix.dev/pixi-build-backends",
    "https://prefix.dev/conda-forge"
]

[tasks]

[dependencies]
bzip-two = { path = "./recipes/bzip-two" }

and a recipe.yaml that looks like:

package:
  name: bzip-two
  version: 1.0.8

[tdejager]

Some linting errors!

[wolfv]

For sure, but maybe you guys can check if this is going in the right direction :)

[tdejager]

I think this would still need a proper error if pixi build is called on a toml without a build-section and no recipe.yaml. Or maybe I missed this.

[tdejager]

For sure, but maybe you guys can check if this is going in the right direction :)

Seems like a useful default for sure!

[nichmor]

For sure, but maybe you guys can check if this is going in the right direction :)

looks like a reasonable direction to me!

[wolfv]

I cleaned up my changes, and just discussed the requirement for [package] and [build-system]. We determined that that is a bug - we should not take the "parent" channels but rather take the channels of the thing we're building.

So this should go away, but IMO that is a follow up PR we should do.

I would argue we can merge this as is now, and then iterate further.

[nichmor]

Looks good !
boring request: could we add a smoke test for this in integration_python/test_build.py?

[wolfv]

Let's add a proper test once the pixi.toml works properly without a build system and package.

I done the changes! :)