feat(build): emit license

[bluwy]

Description

closes #17892
supersedes and closes #18104

Very crude implementation for license support. It supports outputting to .vite/license.md by default, however you can set a path with .json to output in .json format for further processing.

It doesn't contain all dependency package.json information or all features of https://github.com/mjeanroy/rollup-plugin-license. I don't think we should implement all of it, but we could expose more information to be sufficiently flexible for extending or customizing the output. It also does not contain licenses for the project itself.

Open to discussion of how the API and output should look like. You can check out the snapshot tests for example of the current output.

[sapphi-red]

I wonder if we should add a comment that includes link to the license file. TerserWebpackPlugin adds them.

The API and the implementation looks good to me. I even think that the current information is sufficient. I think this feature should focus on license compliance and I believe all the necessary information is included in the license file.

(Sorry that it took almost an year 🙏)

[bluwy]

Better late than never 😄

I wonder if we should add a comment that includes link to the license file. TerserWebpackPlugin adds them.

Do you mean for the inline legal comments, we rewrite it as a link to the output file we generate? It's a bit tricky to do that I think as the output file may not be the final file if it was postprocessed. Or perhaps it's hosted in a different place.

Maybe it's something we can support later though as it requires a new option, and on the topic of more options, maybe it's more scalable if the types are boolean | { fileName: string } now instead of boolean | string.

[sapphi-red]

I wonder if we should add a comment that includes link to the license file. TerserWebpackPlugin adds them.

Do you mean for the inline legal comments, we rewrite it as a link to the output file we generate? It's a bit tricky to do that I think as the output file may not be the final file if it was postprocessed. Or perhaps it's hosted in a different place.

I guess yes, I was thinking of adding a comment like // License information can be found in ../license.md. Hmm, maybe it's fine by just adding a document how to achieve it (e.g. add an example using banner).