--script and --lib flags

[dsp]

• fix missing space in init --build-system flag description

• init: add support for --bin
  --lib and --lib-rs,This adds support for three new flags which determine the templates
  we generate:

1. We adding --lib, which will generate the standard python library
   We no longer generate [project.scripts] section and updated
   the template.
2. We added --script, which will generate a package with a main.py,
   init.py and an entry to [project.scripts]. __main__.py follows
   semantics found in Python packages such as ensurepip and `pip.
3. We added simple tests. Tests do not cover yet --lib and --build-system=maturin.
4. We added a short section about executable projects to docs/guide/basic.md
5. We moved all in init.rs to a templates folder and use include_str!().

[dsp]

Adding this as a draft to get feedback, while I am working to add tests.

[mitsuhiko]

I think this looks good, I'm however not sure if --lib-rs is a good idea. I do however also recognize that this build system thing is odd / verbose.

[dsp]

I think this looks good, I'm however not sure if --lib-rs is a good idea. I do however also recognize that this build system thing is odd / verbose.

My reasoning here is that these options determine the template used. The intuition here is that I likely know the kind of project i want, but leave the specifics of build system choice, etc to rye to choose. This means that rye has "sane default' switch for a template. For instance --lib and --bin implying hatchling and --lib-rs implying maturin. If in the future some new build system comes out and rye chooses this, we can flip the switch to have --lib-rs imply something else.

[dsp]

The counter argument btw is that we want to implment a PyO3/Maturin template for --bin as well. Instead of then having an awkward --bin-rs we just have any combination of --build-system and --bin and --lib flags.

So our choices are effectively:

1. Only keep --bin and --lib, build system choises the specific template choosen.
2. Add --lib-rs and treat them all as explicit template choices. This means later we might need --bin-rs, etc.
3. Some alternative solution (e.g. --lib=rust)
   Happy to go with whatever your preferred choice for rye is. The more i think, the more I actually think adding a template for the --bin --build-system=maturin case is the best choice and just go with --lib and --bin.

Notable I am not happy with --bin because technically it's not a binary that we are producing and thought about --script or --executable. I am not sure about a good alternative.

[mitsuhiko]

I would go with --lib and --bin and then use the build system for the template. It can always error out and say it's not a sensible combination. I also agree that --bin is weird. Maybe it should be called --script instead?

[dsp]

• added tests.
• added changelog entry.
• added an entry to docs/guide/basic.md
• refactored how we deal with templates in init.rs (this is deliberately the last commit and can be dropped, if needed)

[mitsuhiko]

I know people love __main__ but do we think it's a good idea? At least personally I really try to avoid it. Not sure how others feel about it.

[dsp]

I looked into common Python packages like ensurepip, pip, etc. They all provide __main__.py so that you can do python -m pip for example. I think it is good to provide a way so people can run python -m my-package from a rye project. That's why i included it as a thin wrapper around init

[mitsuhiko]

This looks good!