Email example from python docs doesn't validate: Address as EmailMessage header #2863
Description
EmailMessage.__setitem__ should support Address as a value. At least the Python docs email example think it does. See https://docs.python.org/3/library/email.examples.html
test_mypy.py:
from email.message import EmailMessage
from email.headerregistry import Address
msg = EmailMessage()
msg['From'] = Address("Pepé Le Pew", "pepe", "example.com")
And then:
$ mypy test_mypy.py
test_mypy.py:5: error: Incompatible types in assignment (expression has type "Address", target has type "Union[str, Header]")
Activity
srittau commentedon Mar 13, 2019
True. Patches welcome!
arjennienhuis commentedon Mar 13, 2019
I'm not sure how. Maybe:
_HeaderType = Union[str, Header, ContentTransferEncodingHeader, ContentTypeHeader, UniqueDateHeader, SingleAddressHeader, AddressHeader, UniqueAddressHeader, UniqueSingleAddressHeader, MIMEVersionHeader, UniqueUnstructuredHeader, DateHeader, ContentDispositionHeader]Or just:
_HeaderType = Anyarjennienhuis commentedon Mar 13, 2019
msg['From'] = 2actually runs, so maybe:_HeaderType = objectmessage.pyi: Now takes Address as EmailMessage header.
gagbo commentedon Apr 16, 2019
I don't really like using
Anyhere, it feels like it's defeating the purpose of typing. I prefer the big union_HeaderTypeas a fix to this problem.I think
BaseHeader(and all the other Header types mentionned above) should be part of the union for_HeaderType, especially since the documentation says that__getitem__returns aBaseHeaderinstance more often than not.I don't know how to make overloads so that if
email.headerregistry.HeaderRegistry.use_default_map is Truewe can type the default mappings correctly.Also, it would be nice if we were able to deduce the policy from a message, in a way that, for example,
message['date']would be inferred to be anOptional[UniqueDateHeader]for most default policies. But it looks like there's a lot of typing involved for this.gagbo commentedon Apr 16, 2019
This seems to work because the getitem and setitem have different behaviours : while the getitem mostly returns BaseHeader, the setitem seems to dynamically build a class with a parser which takes any object to build a header from. So I think aliasing
_HeaderTypetoobjectis not great eitherarjennienhuis commentedon Apr 16, 2019
But there is this:
msg['Date'] = datetime.datetime(2020, 2, 2)arjennienhuis commentedon Apr 16, 2019
So
__getitem__can return aBaseHeaderbut__setitem__should acceptobjectorAnygagbo commentedon Apr 16, 2019
I'm okay with this too :
BaseHeaderto the union of_HeaderTypesoemail.message.EmailMessage__getitem__can return a BaseHeader without difficulties.email.headerregistryare derived fromBaseHeaderso they can also work there (BaseHeaderkind of specifies that the specialized Header have the same interface). This will keep the changes in_HeaderTypeminimal, and allow all kinds of(Date|Address|...)Headerto be used as_HeaderTypeif need be.email.message.EmailMessage.__setitem__accept anythingutkarsh2102 commentedon Apr 17, 2019
This workaround makes more sense to me, instead of the above one, no?
At the moment, #2924 implements
Any, let me know how should I edit the same.arjennienhuis commentedon Apr 18, 2019
Returning a Union is not ok. See python/mypy#1693
message.pyi: Now takes Address as EmailMessage header.
message.pyi: Now takes Address as EmailMessage header.
message.pyi: Change HeaderType to Any (#2924)