PageCache storing headers in lower format

[nadar]

We are using PageCache to cache a REST response, it seems that headers are always returned as lowercase chars afterwards, but the original input is case sensitive.

https://github.com/yiisoft/yii2/blob/master/framework/filters/PageCache.php#L281

Whats the reason for this behavior? The default active data provider headers are f.e X-Pagination-Page-Count but when cached it returns x-pagination-total-count afterwards.

[samdark]

ac623ab can't remember exact reason for it.

[nadar]

We are describing the headers in an openapi file, so this leaves us in a bad situation, because the header names changes after caching :-)

[samdark]

@bizley, @rob006 maybe you remember the reason?

[nadar]

I will do some more research today, and make some more tests. I also found this, https://stackoverflow.com/a/5259004/4611030 i was not aware of that, but i even if this should considered as best practice, then all headers should be lowercase whether they are cached or not. What also makes me curious is the fact that i am the first person complain about this after 7 years, sounds unlikely to me for such an obvious "issue".

[bizley]

Yes, according to spec header names should be case insensitive unless something changed that I'm not aware of.

[nadar]

If a debug the restoreResponse() function here, i can see the lower case headers:

But CURL, chrome devtools and even Postman return the headers ALL Case Sensitive... wow this confuses me even more now.

Do those tools camel case the headers for better readability....?

[bizley]

I think it's oldest typical story with specs everywhere - we can have them but for some folks these are just "suggestions". I would do the Symfony approach and lowercase them internally for processing but leave them as-is for storing/displaying/sending/outputting etc..

[bizley]

In the mentioned commit we can see:

HTTP header names (case-insensitive) indicating which HTTP headers can be cached.
* Note if your HTTP headers contain sensitive information, you should white-list which headers can be cached.

[bizley]

I can see that Symfony is lowercasing the headers for processing purposes but keeping them as-is when resending.

[bizley]

I'm looking into this and looks like we could store original header name along the normalized ones but I've got one question - if you are storing the same (case-sensitive wise) header several times just under the different case-style which one should be stored as a not normalized name? I would say the last one.