Miss-leaded error message while building with invalid package metadata

[davidlatwe]

Hi everyone 👋🏼

While I was trying to rez-build my Python project, I got an error message saying that I have no build system to use :

01:21:32 ERROR    BuildSystemError: No build system is associated with the path ...

But the doc says if package.py have build_command attribute, custom build system should be used.

Here's what my package.py looks like:

name = "foo"

authors = ["davidlatwe"]

description = "Awesome foo"

version = "0.1.0"

requires = [
    "python*",
]

variants = [
    ["default"],
]


build_command = "some fancy command"


def commands():
    env.PYTHONPATH.append("{this.root}")

I think my package.py was fine, at least should be enough to summon custom build system.

So I start to hunt the cause, and I found it was because my required package "python*" some how failed the schema validation.

And here's the reason why the PackageMetadataError and PackageRequestError was not raised :

https://github.com/nerdvegas/rez/blob/103270d1b39e139223dec706236cbaffc4e14669/src/rez/build_system.py#L31-L36

Any reason why it's being ignored ? I think there should be at least a warning message. 🤔

[instinct-vfx]

I agree that the error is somewhat misleading. python* is not a valid request though, so the fail itself is expected. What did you want to request? Any python version? That would be just python. The reason for your string not to be a valid request is that Rez uses - as a separator between package name and version. If there is no -, then Rez considers the whole string to be the package name and * is not a valid character for package names, hence the schema validation fails.

See also the help on package attributes for the name attribute: https://github.com/nerdvegas/rez/wiki/Package-Definition-Guide#name
Only alphanumerics and underscores are allowed as package names.

[davidlatwe]

Thanks for the info ! Yes, I changed the request package name to python or python-* and it resolved. 👍🏼

[nerdvegas]

Agreed this should be a warning, I'll make this change. Please be aware that by specifying `python-*`, you're specifically using something called "requirements expansion" (which is fine), see https://github.com/nerdvegas/rez/wiki/Package-Definition-Guide#requirements-expansion Cheers A

…

On Sun, Aug 2, 2020 at 6:58 AM David Lai ***@***.***> wrote: Thanks for the info ! Yes, I changed the request package name to python or python-* and it resolved. 👍🏼 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#915 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAMOUSRWQB6XETA64D7OBY3R6R6WJANCNFSM4PR5OABQ> .

[nerdvegas]

Actually I'll make this an error - this then matches existing behaviour when build system is know (eg, a CMakeLists.txt is present)