http.cookies.BaseCookie.load() applies partial state before raising CookieError

Bug description

BaseCookie.load() parses the cookie string in two phases: parse then apply. The comment says it rejects the string if syntactically invalid. However, _is_legal_key() validation runs during the apply phase (inside Morsel.set()), not the parse phase. Cookies before an illegal key are applied to the jar before CookieError is raised.

from http.cookies import SimpleCookie, CookieError

C = SimpleCookie()
try:
    C.load("a=1; b,c=2; d=3")
except CookieError:
    pass
print(len(C))  # 1, expected 0

Related to gh-84183 but distinct: that issue is about raise-vs-silent for different invalid inputs; this is about partial state when CookieError IS raised.

CPython versions tested on

3.13, 3.14, main

Operating systems tested on

macOS

Linked PRs

• gh-154674

Comece em http.cookies.BaseCookie.load() e reproduza o problema com a stringa de cookies mostrada no relatório. Verifique se um CookieError deixa o cookie jar vazio; o corpo da issue contém um link para a PR gh-154674, portanto verifique esse trabalho antes de prosseguir.