Compatibility with Cache Control Override: is max-age=0 really necessary for BigPipe's placeholders?

Even though this is a test can we setup a test to check for the cache age?

The patch in #8 makes big_pipe responses cacheable when using big_pipe_sessionless and cache_control_override but it does not correctly bubble the cache tags from elements rendered by big_pipe.

BigPipe::sendPlaceholders() calls sendChunk() with the chunk as a string.
This means that sendChunk() never gets the cache tags and max age from these chunks.

BigPipeSessionless::sendChunk() is able to use the chunk's cache parameters and apply them to the final cached page.
If core does not send these cache parameters, cache tags from elements rendered by big_pipe will not bubble to the cached response.
This means page cache can store a page even if it contains a block with max-age = 0 rendered by big_pipe; because its max-age will not bubble to the stored response.

The attached patch makes core pass the chunk cache tags to big_pipe_sessionless.

Looks like #18 needs review.

The Needs Review Queue Bot → tested this issue. It no longer applies to Drupal core. Therefore, this issue status is now "Needs work".

This does not mean that the patch needs to be re-rolled or the MR rebased. Read the Issue Summary, the issue tags and the latest discussion here to determine what needs to be done.

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