[wp-trac] [WordPress Trac] #62046: `render_block_context` filter works differently on top-level vs. inner blocks

[WordPress Trac]

#62046: `render_block_context` filter works differently on top-level vs. inner
blocks
--------------------------+-----------------------------
 Reporter:  dlh           |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Editor        |    Version:  5.9
 Severity:  normal        |   Keywords:
  Focuses:                |
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 The `render_block_context` filter has a different effect depending on
 whether the block being rendered is a top-level block or an inner block.
 When the block is a top-level block, then context provided with
 `render_block_context` is made available as context to its inner blocks.
 When the block is an inner block, the context provided with the filter
 isn't made available to its inner blocks.

 By "top-level block," I mean a single block that's rendered with
 `render_block()`, such as within `do_blocks()`. By "inner block," I mean
 an inner block rendered within `WP_Block::render()`.

 I think this difference in behavior can be traced back to when the filter
 is applied.

 The logic to make context available to inner blocks occurs within the
 `WP_Block` constructor. In `render_block()`, the value returned by the
 `render_block_context` filter is passed to the new `WP_Block` object, so
 the filtered value is the one made available to inner blocks.

 Within `WP_Block::render()`, the `WP_Block` object for the inner block has
 already been instantiated (in `WP_Block_List`). The value returned by
 `render_block_context` is assigned directly to the inner block's
 `$context` property, so the logic in the constructor to provide that
 context to deeper inner blocks isn't invoked.

 The linked PR contains a unit test demonstrating this behavior. The test
 is derived from the real situation in which we observed it: A custom block
 capable of passing `query` context to an inner `core/post-template` block
 via `render_block_context`. The post template block received the expected
 context when the custom block was a top-level block but not when it was an
 inner block, such as inside a group.

 `render_block_context` was applied to inner blocks in #51612 along with
 related filters, and there's quite a bit of discussion there about when
 exactly to apply them, so the logic in place now certainly has reasons
 behind it.

 Still, I would expect the filter to behave the same way with respect to
 inner blocks regardless of where in the tree the block being filtered is.
 Between the two options, I would expect the filter to behave like it does
 in `render_block()`: Context supplied with a filter is made available to
 inner blocks.

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Ticket URL: <https://core.trac.wordpress.org/ticket/62046>
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