Failing test with Rack::MockResponse

[tenderlove]

This PR removed checking for transfer-encoding from the Rack::Response object when deciding whether or not to set the content-length header. This had an impact on the Rack::MockResponse subclass as the mock response subclass will try to buffer the response immediately inside the initialize method. When the response is buffered, the @length instance variable is set, and this causes the superclass to set the content-length header even though it's a streaming response.

I'm unsure how to fix this situation, so this PR is just a failing test that demonstrates the problematic behavior. Even though the chunked body object doesn't respond to to_ary, the mock response object decides to buffer it anyway, causing the "content length" header to be set. I tried returning early from buffered_body!, but this causes other issues surrounding when the body should be "closed" (it turns tests will try to read the response body twice, but the second time it is closed).

Ref: rails/rails#52066
Ref: rails/rails#52092

[jeremyevans]

I propose reverting #2195 to fix the issue. When I approved it, I was not aware of what was depending on the previous behavior.

[tenderlove]

I propose reverting #2195 to fix the issue. When I approved it, I was not aware of what was depending on the previous behavior.

Ya, I think we should. I agree that theoretically #2195 is the right thing to do, but it seems like we need to take more situations in to account before we can do it. "Testing + streaming responses" seems like perilous territory and we should figure out what to do there before we redo #2195

[ioquatix]

and this causes the superclass to set the content-length header even though it's a streaming response.

By the time Rack::MockResponse gets the body, and processes it, it's no longer streaming, because Rack::MockResponse behaves like a client and reads all the chunks into a single buffer. I'm not sure if this is the correct behaviour or not, but it seems reasonable to me. However, as we can see, it's also problematic.