[ovsx] Provide an API to check whether a license is present and compliant

[HaaLeo]

Description

Reading Brian King's blog especially the sections "Timeline" and "Licensing" I thought that the GitHub action (HaaLeo/publish-vscode-extension) probably should check whether an extension has a license file and whether it is an "Open VSX friendly" license.

To do that it would be best when the ovsx package offers some API method to check whether the extension's license is compliant with the Open VSX / Eclipse guidelines.

Proposal

Export some method, for example isLicenseOk which checks whether the repository includes a license and whether it is compliant with the guidelines.

Further, the ovsx package probably wants to perform this check also when it is invoked with a pre-bundled .vsix file (via the --extensionFile option).

[spoenemann]

Hi @HaaLeo! There are no constraints on the license except that there has to be one. The presence of a license is checked in the server when an extension package is processed, so there's not really a need to check in the client.

The ovsx package currently does check for presence of a license, but only to provide the user with the option to choose MIT in case they have no license:
https://github.com/eclipse/openvsx/blob/master/cli/src/check-license.ts

That interactive function doesn't make sense in the context of a GH Action, so if you like we could extract the actual presence check to a separate function.

[HaaLeo]

Hi @spoenemann thx for your reply. I was unsure whether the server already checks for an extensions license or not.

Exporting the presence check would be beneficial, because then the action could yield a warning message also when an extension is only packaged and not published (via the --dryRun flag).

However, thank you for clarifying the issue 🙂

[vymarkov]

@spoenemann I found another very useful case where we could improve process of adding new extensions into extensions.json, currently we don't perform any checks during adding new extension into this list, but Open VSX requires licence to be present, thus it make sense to extract check licence to a separate function.

Then use this function during add step to prevent adding to extensions.json extensions which could not be published if licence is not present or publishing (afaik, this repo could be used to publish extensions to any kind of marketplace, not restricted to Open VSX) if we wanna leave the opportunity to use this repo as a source of extensions.

I would like to open a pull request in near future to accomplish this goal.

[vymarkov]

@spoenemann hi, I've just opened a pull request with changes that we mentioned on this issue #234 please take a look at this PR :)

Thanks in advance!