Task description needs fleshing out. What is PSR-7 (a TLDR version at least, rather than just a link elsewhere)? Why? What does this do for us? Just allowing us to implement PSR-15? Or do we get other benefits too?

In T194397#4197272, @Reedy wrote:

Task description needs fleshing out. What is PSR-7 (a TLDR version at least, rather than just a link elsewhere)? Why? What does this do for us? Just allowing us to implement PSR-15? Or do we get other benefits too?

I mean I think there's value in having a "standard" request/response pipeline using industry-standard request and response interfaces, however, there's not really a huge advantage in that if we can't plugin middlewars (or abstract some of our code as middlewares).

In practice I suppose this would mean:

• WebRequest should implement ServerRequestInterface
• WebRequestUpload should probably implement UploadedFileInterface
• WebResponse should implement ResponseInterface
• MWHttpRequest should implement RequestInterface (which is fairly useless for interoperability; software that aims for that should probably implement PHP-HTTP as well)

Implementing PSR-7 + PHP-HTTP for MWHTTPRequest would mean that it could be easily used outside of MediaWiki (I doubt there is much use case for that; maybe if we had PHP-based microservices and wanted them to have all the query-parameter-wrangling behavior of MediaWiki?) and it could be easily replaced via the service container with another library (that seems useful; MWHttpRequest does not offer much in terms of features). Implementing PSR-7 in WebRequest / WebResponse does not seem directly useful (it would be a requirement for PSR-15 compliance though).

MediaWiki-REST-API did implement PSR-7. Not sure there is much value in doing it also for MwHttpRequest, or the action API, or WebRequest/WebResponse.