Hello,

I just ran into an issue with Symfony 3.1.5 concerning the HttpCache mechanism, which sends back the content of a GET method while executing an OPTIONS call.
I have a JS application which calls an API. This app uses CORS preflight OPTIONS calls to determine if he can call the API. Cache is configured on some public APIs.

On a basic example here is what happens:

• OPTIONS call from the JS app returns the right Response with headers such as "access-control-allow-methods: GET" and "cache-control: no-cache" (if I do it multiple times using Postman it always generates a new Response with the expected content, so that I am sure it is not cached)
• GET call issued just after returns a Response with headers such as "cache-control: max-age=86400, public, s-maxage=86400" (this one is being cached by HttpCache, which stores it in a file on the server)
• But when another computer accesses the page, the OPTIONS call returns a cached Response, with "cache-control: max-age=86400, public, s-maxage=86400"

I found that because the Store::generateCacheKey() method only uses the Uri to compute the cache the key, then HttpCache thinks it has found a cached version of the OPTIONS call and sends back the headers and body of the GET call instead.

I think the generateCacheKey should at least use the method when computing the key, and maybe headers like Accept-*.