[wp-trac] [WordPress Trac] #56068: Send HTTP headers after querying posts in WP::main()

[WordPress Trac]

#56068: Send HTTP headers after querying posts in WP::main()
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 Reporter:  SergeyBiryukov  |      Owner:  (none)
     Type:  enhancement     |     Status:  new
 Priority:  normal          |  Milestone:  Awaiting Review
Component:  Bootstrap/Load  |    Version:
 Severity:  normal          |   Keywords:  has-patch needs-unit-tests
  Focuses:                  |
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 When trying to add or adjust some HTTP headers via the `wp_headers` filter
 or `send_headers` action, the `$wp_query` global is mostly empty and
 conditional tags don't work as expected, as posts have not been queried
 yet.

 The earliest action where conditional tags like `is_front_page()` work
 correctly is currently `wp`.

 In a discussion with @jonoaldersonwp and @joostdevalk it was pointed out
 that moving the `send_headers()` call after `query_posts()` in
 `WP::main()` would provide better context and more flexibility when
 manipulating HTTP headers. Implementing that seems to work in my testing,
 and all existing unit tests still pass.

 If that happens, we could also move the `X-Pingback` header, which is
 currently [source:tags/6.0/src/wp-includes/class-wp.php?marks=704-707#L702
 sent in handle_404()] after posts have been queried, as of [34442] /
 #20226, to a more appropriate place, which is `send_headers()` :)

 However, that means sending headers after `WP_Query` runs all the post
 queries, filters, etc. and I'm curious if there are any performance
 considerations that should be taken into account here.

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Ticket URL: <https://core.trac.wordpress.org/ticket/56068>
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