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

http.cookies.BaseCookie.load() から始め、報告に示されている Cookie 文字列で問題を再現してください。CookieError によって cookie jar が空のままになることを確認してください。issue 本文には PR gh-154674 へのリンクがあるため、先にその作業を確認してください。