Debug bar breaks Xdebug session when redirect occurs

[richard-ejem]

Scenario:

• use Tracy\Debugger::enable() and place it after a possible redirect (i.e. to a language-specific url, like http://example.com/ -> http://example.com/en; should not happen in Nette application with standard bootstrap, happened to me in Drupal project using Tracy)
• the redirect occurs when loading Tracy assets (like http://example.com/?_tracy_bar=js&v=2.4.2&XDEBUG_SESSION_STOP=1&XDEBUG_PROFILE=0&XDEBUG_TRACE=0 is redirected to http://example.com/en?_tracy_bar=js&v=2.4.2&XDEBUG_SESSION_STOP=1...
• problem: header_remove('Set-Cookie') is not called from Bar.php when the redirect occurs and the cookie XDEBUG_SESSION=deleted gets into browser

I've proposed a simple solution printing at least console warning to confused developers like me, who would be investigating for hours why XDEBUG stops after first request, will pull request it in a second :)

[richard-ejem]

Thanks to @JanTvrdik for commenting original pull request, I just found even simpler way to detect and fixed the pull request with a single simple commit :)

[dg]

What about this 6a24bb6?

[richard-ejem]

@dg unfortunatelly not helping, tested on my project :( I will provide some minimal case to reproduce the problem soon

[dg]

It closes XDEBUG session, but it should close it only once.

[richard-ejem]

Take a look at this MWE: https://github.com/richard-ejem/tracytest
try debugging it in browser, debugger stops working after removing the XDEBUG_SESSION_START argument from URL.

[dg]

I see, dispatchContent() is not loaded…

[richard-ejem]

ok so maybe please re-open the issue?
My suggested fix was just to notify users about the problem, as any redirect before Debugger::enable() when XDEBUG_SESSION_STOP is passed will cause this problem.
Just checked sources of Xdebug, there seems to be no way to stop Xdebug for a single request without destroying the cookie.
Other solution would be to create pull request for Xdebug to add something like XDEBUG_SKIP=1 which would disable Xdebug just for the single request, but it will take long to be merged and downloaded by most users.

Sorry, just noticed that the revert commit fixed the issue.

[richard-ejem]

But there is still one edge case where it can cause problems, see current https://github.com/richard-ejem/tracytest .
In short:

• I do a state-changing action on some URL (add stuff to cart)
• it happens before Debugger::enable()
• I forget to redirect after that action

Would be my bad, that I didn't place a redirect on state-changing URL, but I will really wonder why 4 items are added to my cart instead of 1.

This is merely hypothetical, but maybe should still be considered as a debug tool should cause minimum possible side effects.

[dg]

This tool must be simply called first in script, otherwise it is not used correctly. I really dont know how handle these cases.

[dg]

I'm thinking that might be a better solution is yours, just write out a warning.