API for getting the full Swift version (as reported by `swift --version`)

[grynspan]

Motivation

Swift Testing needs to be able to report the full Swift version (as reported by swift --version) for diagnostic purposes, e.g. when reading logs produced by a CI job or another engineer or in a different configuration. This version information is immensely useful when filing bug reports because it allows us to immediately see "oh, it was the [e.g.] August 9th nightly main-branch toolchain where the bug occurred" and so on.

Proposed solution

I'd like to propose we add API to the Swift standard library that vends a "human-readable" string equivalent to the aforementioned one. Something like this would be sufficient:

/// The human-readable version of the standard library.
///
/// Rabble rabble details details nuances nuances.
public var standardLibraryVersion: String { get }

Alternatives considered

• An internal-only, C/C++, or SPI function could also work, but as it wouldn't be API, developers not working on the Swift project wouldn't be able to use it.
• A more complex interface with configuration options is probably overkill.

Additional information

No response

[grynspan]

Also, Swift Package Manager could adopt the same API so that it doesn't need to fake it for subcommands like swift test --version (which produce very different strings.)

[hassila]

This would also be great of benchmarks to print out, we got this issue filed that we can't currently nicely solve without proper API:

ordo-one/package-benchmark#213

[JaapWijnen]

Wouldn't it also be nice if this was available at compile time somehow? To be used in compiler directives like #if perhaps?

[grynspan]

That would be feasible if it were exposed as a string literal macro, I think.

[Azoy]

The version of the standard library is very independent from what the compiler's version is from e.g. swift --version.

[grynspan]

That's fair enough. We're specifically interested in the more verbose version info here as it's very helpful for triaging bug reports down to specific commits.