Require a method to avoid vendoring target deps that will never be used

[flukejones]

Problem

This is best illustrated with some screenshots.

I have a project that will only ever be built for Linux. I don't see any obvious way to specify this as such and so I'm not sure how best to handle it. But it is an issue because this project gets built on external servers for packaging for distros, and having such an absurdly high vendoring size can adversely affect these constrained environments.

Proposed Solution

Something along the lines of:

[package]
name = "named_thing"
version.workspace = true
license = "MPL-2.0"
target = "unix"
target_arch = "x86_64"

which would then restrict all chained [target.'cfg(TARGET_OS)'.dependencies] automatically as they could then never be built, and as such vendoring for these targets can be fully ignored.

Notes

No response

[weihanglo]

Thanks for the report.
Feel like this is a duplicate of #7058 to some extent. The solution of each of them is very likely the same.

[weihanglo]

These are all feature requests for partial vendoring:

• vendor only certain crates or only crates from certain sources #9234 for vendoring from certain sources.
• Support for vendoring on a single platform #7058 for vendoring on certain platforms.
• Support vendoring for a feature set #9980 for vendoring on a certain feature set.

[flukejones]

Sounds like a much needed feature then. Especially for target-os and feature sets, where both of these would contribute heavily to reduced source package sizes for Linux distribution builds.

[weihanglo]

Thanks. I'll close this in favor of the aforementioned issues.