Session: keep exceptions chain on session_start

[forrest79]

• new feature
• BC break? no

There was an issue #208 - phpredis session driver was raising a notice, when session lock can't be obtained. Nette Session was correctly converting this notice to an exception. The strange was, that even the notice was raised, session_start returned true (it was phpredis problem).

Now, the new production version of phpredis is out, and the behavior is a little bit different. If a lock can't be obtained, instead of notice, the warning (instead of a notice) is raised and the session_start returned correctly false.

The problem is, I need to know the reason why the session wasn't started (when redis is death, it's a problem, when session lock can't be obtained, it's probably OK - user is probably doing many parallel requests). Nette\Utils\Callback::invokeSafe around the session_start method correctly converts warnings to exceptions, but now, there are two exceptions:

• the first is from the phpredis - something like Failed to acquire session lock
• the second is from the PHP itself Failed to read session data: redis (path: tcp://server:6379?timeout=3&database=1&prefix=session:v1:)

And the first one is overwritten with the second one, that is thrown to the app. But I need to know also the first one :-)

So my first idea is to set correct previous exception property and in the app, I have the complete exceptions chain, that I can read and get the correct session problem.

[dg]

thanks