[YoutubeDL] Introduce YoutubeDLCookieJar and clarify the rationale be…

…hind session cookies (closes #12929)

youtube_dl/YoutubeDL.py

@@ -88,6 +88,7 @@
     version_tuple,
     write_json_file,
     write_string,
+    YoutubeDLCookieJar,
     YoutubeDLCookieProcessor,
     YoutubeDLHandler,
 )
@@ -558,7 +559,7 @@ def __exit__(self, *args):
         self.restore_console_title()
 
         if self.params.get('cookiefile') is not None:
-            self.cookiejar.save()
+            self.cookiejar.save(ignore_discard=True, ignore_expires=True)
 
     def trouble(self, message=None, tb=None):
         """Determine action to take when a download problem appears.
@@ -2297,16 +2298,9 @@ def _setup_opener(self):
             self.cookiejar = compat_cookiejar.CookieJar()
         else:
             opts_cookiefile = expand_path(opts_cookiefile)
-            self.cookiejar = compat_cookiejar.MozillaCookieJar(
-                opts_cookiefile)
+            self.cookiejar = YoutubeDLCookieJar(opts_cookiefile)
             if os.access(opts_cookiefile, os.R_OK):
                 self.cookiejar.load(ignore_discard=True, ignore_expires=True)
-                # Force CookieJar to treat 'expires=0' cookies as session/discard cookies
-                # Fixes https://bugs.python.org/issue17164
-                for cookie in self.cookiejar:
-                    if cookie.expires == 0:
-                        cookie.expires = None
-                        cookie.discard = True
 
         cookie_processor = YoutubeDLCookieProcessor(self.cookiejar)
         if opts_proxy is not None:

youtube_dl/utils.py

@@ -39,6 +39,7 @@
     compat_HTMLParser,
     compat_basestring,
     compat_chr,
+    compat_cookiejar,
     compat_ctypes_WINFUNCTYPE,
     compat_etree_fromstring,
     compat_expanduser,
@@ -1139,6 +1140,33 @@ def https_open(self, req):
             req, **kwargs)
 
 
+class YoutubeDLCookieJar(compat_cookiejar.MozillaCookieJar):
+    def save(self, filename=None, ignore_discard=False, ignore_expires=False):
+        # Store session cookies with `expires` set to 0 instead of an empty
+        # string
+        for cookie in self:
+            if cookie.expires is None:
+                cookie.expires = 0
+        compat_cookiejar.MozillaCookieJar.save(self, filename, ignore_discard, ignore_expires)
+
+    def load(self, filename=None, ignore_discard=False, ignore_expires=False):
+        compat_cookiejar.MozillaCookieJar.load(self, filename, ignore_discard, ignore_expires)
+        # Session cookies are denoted by either `expires` field set to
+        # an empty string or 0. MozillaCookieJar only recognizes the former
+        # (see [1]). So we need force the latter to be recognized as session
+        # cookies on our own.
+        # Session cookies may be important for cookies-based authentication,
+        # e.g. usually, when user does not check 'Remember me' check box while
+        # logging in on a site, some important cookies are stored as session
+        # cookies so that not recognizing them will result in failed login.
+        # 1. https://bugs.python.org/issue17164
+        for cookie in self:
+            # Treat `expires=0` cookies as session cookies
+            if cookie.expires == 0:
+                cookie.expires = None
+                cookie.discard = True
+
+
 class YoutubeDLCookieProcessor(compat_urllib_request.HTTPCookieProcessor):
     def __init__(self, cookiejar=None):
         compat_urllib_request.HTTPCookieProcessor.__init__(self, cookiejar)