Fixing errors of a new project does not make it clear that non-OSI-approved license may be used

[nagisa]

$ cargo new banana
     Created library `banana` project
$ cargo publish
    Updating registry `https://github.com/rust-lang/crates.io-index`
warning: manifest has no description, license, license-file, documentation, homepage or repository.
...
error: api errors: missing or empty metadata fields: description, license. Please see http://doc.crates.io/manifest.html#package-metadata for how to upload metadata
# add
# description = "this is a banana"
# license = "TBA"
$ cargo publish
    Updating registry `https://github.com/rust-lang/crates.io-index`
warning: manifest has no documentation, homepage or repository.
…
error: api errors: unknown license or other term: TBA; see http://opensource.org/licenses for options, and http://spdx.org/licenses/ for their identifiers
# From the error above assume non-OSI license cannot be used T_T

The errors should make it clear what all the alternatives/valid values are. For example nowhere it is stated (other than in documentation), that license = "custom" is a valid option.

[nagisa]

A bit unrelatedly, the errors from the API should probably not exposed verbatim.

Please see http://doc.crates.io/manifest.html#package-metadata for how to upload metadata

for example is very irrelevant to a cargo user.

[steveklabnik]

that license = "custom" is a valid option.

To be clear, it's not; you use license-file and point to a file locally instead.

[ehuss]

I'm going to close as this is effectively solved by rust-lang/crates.io#6545.

I don't know if cargo should be validating license expressions itself so that you can get earlier feedback, and to ensure there is consistency for all kinds of dependencies. However, there are downsides to doing validation in cargo, so that seems a bit up in the air.