[HttpCache] fixed if-modified-since header default to an empty string if the last-modified header was not set

[akalineskou]

… if the last-modified header was not set

The problem I had with this was that the psr http factory would create the request, and would throw an exception because the null value isn't an allowed header value
https://github.com/symfony/psr-http-message-bridge/blob/8564bf76630423ced21bbbee189947b90677dcde/Factory/PsrHttpFactory.php#L72
https://github.com/Nyholm/psr7/blob/55ff6b76573f5b242554c9775792bd59fb52e11c/src/MessageTrait.php#L180

Q	A
Branch?	3.4
Bug fix?	yes
New feature?	no
Deprecations?	no
Tickets
License	MIT
Doc PR

[nicolas-grekas]

Could you please add a test case?

[akalineskou]

Could you please add a test case?

I thought about adding a test for, but I don't how I would go about testing this particular case

[stof]

shouldn't we actually omit the if-modified-since header in case there is not last-modified header instead of setting an empty string ?

[akalineskou]

I've created this repo from scratch to reproduce it
https://github.com/alex2005git/symfony-cache-bug

start the server, open the route, after 1 minute or 2 it should throw Header values must be RFC 7230 compatible strings.

[akalineskou]

shouldn't we actually omit the if-modified-since header in case there is not last-modified header instead of setting an empty string ?

I'm fine with whichever you guys think is best

[akalineskou]

@nicolas-grekas any update on this issue?

[akalineskou]

ping!

[nicolas-grekas]

Omitting the header looks the best yes in this case. With a test case also :)

[nicolas-grekas]

pong @alex2005git :)

[mpdude]

This has been fixed in #34385 already.