Given an (RFC-legal) email address with the local part consisting of a quoted empty string (e.g. 'Nobody <""@example.org>'), when I call the 'addr_spec' property, the result no longer includes the quoted empty string (so, in this case, addr_spec would return '@example.org').

As far as I understand it, this is due to the following code in email.headerregistry.Address.addr_spec (in 3.8 and below):

if len(nameset) > len(nameset-parser.DOT_ATOM_ENDS):
    lp = parser.quote_string(self.username)

or, in the current version on master:

lp = self.username
if not parser.DOT_ATOM_ENDS.isdisjoint(lp):
    lp = parser.quote_string(lp)

Both of these tests will not work with the empty string since the empty string is always disjoint from anything, so it will never get quoted.

It is actually parsed correctly and serialized back when you try to convert it to a string representation:

from email.parser import BytesFeedParser
import email.policy

def main():
    eml_string = 'From: Nobody <""@example.org>'
    parser = BytesFeedParser(policy = email.policy.default)
    parser.feed(eml_string.encode())
    msg = parser.close()
    print(msg.get('From').addresses[0].addr_spec)
    print(repr(msg.get('From')._parse_tree))
    print(msg.as_string())

Running this gives me:


@example.org
AddressList([Address([Mailbox([NameAddr([DisplayName([Atom([ValueTerminal('Nobody'), CFWSList([WhiteSpaceTerminal(' ')])])]), AngleAddr([ValueTerminal('<'), AddrSpec([LocalPart([QuotedString([BareQuotedString([ValueTerminal('')])])]), ValueTerminal('@'), Domain([DotAtom([DotAtomText([ValueTerminal('example'), ValueTerminal('.'), ValueTerminal('org')])])])]), ValueTerminal('>')])])])])])
From: Nobody <""@example.org>


Notice the : AddrSpec([LocalPart([QuotedString([BareQuotedString([ValueTerminal('')])])])

print() converts the addr-spec into a string, which omits the quotes. This is true for any non-none string too:


hello@example.org
AddressList([Address([Mailbox([NameAddr([DisplayName([Atom([ValueTerminal('Nobody'), CFWSList([WhiteSpaceTerminal(' ')])])]), AngleAddr([ValueTerminal('<'), AddrSpec([LocalPart([QuotedString([BareQuotedString([ValueTerminal('hello')])])]), ValueTerminal('@'), Domain([DotAtom([DotAtomText([ValueTerminal('example'), ValueTerminal('.'), ValueTerminal('org')])])])]), ValueTerminal('>')])])])])])
From: Nobody <"hello"@example.org>


If you prefer the string representation of the header's parsed value, you can try:

    print(msg.get('From').fold(policy=email.policy.default))

Which prints:

    From: Nobody <""@example.org>