Package request dict-like object list of packages

[hughetop]

Hello,

For the request object we can do things like:

@late()
def requires():
    packages = []
    if 'PySide2' not in request:
        packages.append('PySide2')
    return packages

This is great, but if you have multiple things you want to check, you need to do each one individually like:

if 'PyQt4' not in request and 'PyQt5' not in request and 'PySide' not in request and 'PySide2' not in request:
    packages.append('PySide2')

Would it be possible to get the list or set of package requests? The request base class only implements __contains__ and __getitem__. Ideally we could do something like:

if not request.intersection({'PyQt4', 'PyQt5', 'PySide', 'PySide2'}):
    packages.append('PySide2')

[JeanChristopheMorinPerso]

Something similar has been tried, but it was iterating over request, see #608. The request object definitely need some enhancements to really make it dict-like. Right now it's partly dict-like.

[hughetop]

Ah, interesting. If the request object had a way to get a copy of the packages, like set(self._data.values()) that could work for iteration and package intersection.