WebProfiler + StreamedResponse = No toolbar

[jkufner]

Q	A
Bug report?	no
Feature request?	yes
BC Break report?	no
RFC?	no
Symfony version	3.3.5

When using Symfony\Component\HttpFoundation\Response to produce some output, the toolbar from WebProfilerBundle is correctly injected before </body> tag. But when using Symfony\Component\HttpFoundation\StreamedResponse the toolbar is not injected.

Would it be possible to inject toolbar into StreamedResponse too ?

Also, this "detail" should be noted in the documentation, so users of the StreamedResponse class won't get surprised.

[stof]

currently, it is not possible, as the event listener has no way to hook into the streamed rendering. and implementing such hook would be very hard, as streaming itself is not performed by Symfony but by your own code (so you would have to provide a hook to Symfony)

[javiereguiluz]

@jkufner thanks for reporting this. You are right about this, but sadly we won't fix it because it's too complicated and not worth it (that's why I'm closing this as "won't fix").

However, as you said, we can mention this limitation somewhere in the docs. We're trying to do that in symfony/symfony-docs#8221

[fabpot]

I don't think it's "too complicated". It's more like that it does not necessarily makes sense. Streaming a response means that there is never a good time to inject the toolbar (besides the technical complexity that we don't have access to the stream).

[jkufner]

Output is available via the $output_callback parameter of ob_start(). So technically it is possible to intercept </body> in the stream just before it is sent to a client.