[BC Break] trimHeaderValues in 1.6 Release

[solverat]

With the new release, all headers are getting asserted by its type. Having said that, this introduces a BC break. Symfony's Browserkit Client for example, passes the https value as a boolean type:

https://github.com/symfony/symfony/blob/38b9b951a42b908fd7e7e9651e41209bc7e620d1/src/Symfony/Component/BrowserKit/AbstractBrowser.php#L385

After updating guzzlehttp/psr7 to 1.6, this request will fail.

[Tobion]

Symfony BrowserKit does not use psr7. How does the boolean https trigger the error? Do you use ServerRequest::fromGlobals? Please provide a reproducer.

[svandervlugt]

I think I hit the same problem.

In 1.6 new GuzzleHttp\Psr7\Response(200, ['Authorization' => null], '') throws an InvalidArgumentException while in 1.5.2 it generates the same as
new \GuzzleHttp\Psr7\Response(200, ['Authorization' => ''], '')

[sagikazarmark]

According to PSR-7 header values must be strings or arrays of strings. 1.6.0 enforces that. While it might be a break from a library point of view, this library is a PSR-7 implementation. Relying on undocumented features is never a good idea.

@Tobion IMHO we should add a warning to the release section saying that this release might break for users not following the PSR-7 specification.

[Tobion]

Fix in #283

[sagikazarmark]

IMHO that should only be the solution, if we add back the assertions to 2.x

[Tobion]

Yes that's a possibility. But let's not do it in 1.6 as it has only been released for 1 day and several people are affected. So more people will follow otherwise.

[GrahamCampbell]

I disagree it's a BC break. Because the param type was string[], the specification says the behaviour is undefined if you pass something else, and changing the behaviour of something outside of the specification shouldn't be regarded as a BC break.

That said, for reasons of practicality, it doesn't make sense to break the Symfony code when there's a simple way to get the old behaviour back. ;)

[sagikazarmark]

☝️

[sagikazarmark]

Fixed in #283