fix(collections): preserve inner blocks in card indicator

[adekbadek]

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Changes proposed in this Pull Request:

Monorepo port of Automattic/newspack-plugin#4726 (by @laurelfulford). The original PR fixed this in the legacy newspack-plugin repo, but the same bug still exists unfixed in the monorepo, which is now the primary release source. Code is from the original PR; this PR carries it to where it ships.

In Collections, the 'Card' Collection Indicator Style reassembled post content from $block['innerHTML'], which drops inner blocks - e.g. core/list-item children of a core/list, or columns in a Columns block. Switching to render_block( $block ) preserves inner blocks (and renders dynamic blocks correctly).

Also includes:

• A regression test (test_insert_after_nth_block_preserves_inner_blocks) asserting <li> items survive.
• An update to the existing test for the WP 7.0+ wp-block-paragraph class now emitted by render_block().

Closes NPPM-2831.

How to test the changes in this Pull Request:

1. On a site running Collections, go to Newspack > Settings > Collections and set 'Collection Indicator Style' to 'Card'.
2. Create a post with a List block containing several items, assigned to a published collection. Publish.
3. View the post on the front-end; before this fix the list renders as an empty <ul></ul> (items dropped). After it, the items appear.
4. Smoke test that the post otherwise renders correctly.

Unit-level: n test-php --filter Content_Inserter (14 tests, 56 assertions). The regression test fails on the old innerHTML code (empty <ul>) and passes with render_block().

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?

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[dkoo]

Confirmed the fix and the blocker (details inline) in manual testing.

Thanks for porting this — the core fix is right and the regression test is a good guard. render_block() is the correct way to reassemble parsed blocks so inner blocks (list items, columns) and dynamic blocks survive, and I confirmed the existing suite (14 tests / 56 assertions) passes on this branch.

One blocker before merge: rendering blocks inside the the_content priority-1 filter introduces a re-entrancy regression. self::$the_content_has_rendered is set only after insert_after_nth_block() runs, so a dynamic block that re-applies the_content during that render (Query Loop / core/post-content, core/template-part, core/post-time-to-read) re-enters the indicator filter with the guard still false. The result: a card-style post that is in a published collection and contains such a block injects the outer post's collection card into the nested/queried post's content — and that output is cached for all readers. I reproduced this in a live env (WP 7.0). It's a one-line fix plus a regression test. There's also a smaller test-brittleness suggestion below.

[adekbadek]

Thanks for the thorough manual review @dkoo - all three points addressed in da9f45b:

• Blocker (re-entrancy / cached card leak into nested the_content): Reproduced first with a failing regression test (a dynamic block that re-applies the_content during render yielded two cards), then fixed by moving the self::$the_content_has_rendered guard above the switch so nested re-entry short-circuits. Test now asserts exactly one card; normal single-post render confirmed unchanged. This was latent in the original PR too, so good thing we re-reviewed on the way over.
• Suggestion (WP 7.0 wp-block-paragraph coupling): Assertions now check inner text + ordering instead of the core wrapper class.
• Nit (lock in inner-block placement): The inner-blocks test now also asserts the <ul class="wp-block-list"> wrapper, that items render within it, and the insert/order positions.

Full suite green (15 tests, 63 assertions).

[dkoo]

Thanks for the updates, @adekbadek! All three points from the previous review are addressed and verified. The guard is now set before the blocks are rendered, so a dynamic block that re-applies the_content during the card render (Query Loop / core/post-content, etc.) short-circuits on re-entry instead of leaking the outer post's collection card into nested/queried content; there's a dedicated regression test asserting the card renders exactly once. The test assertions no longer couple to the WP 7.0+ wp-block-paragraph class, and the inner-blocks test now locks in list-wrapper placement and ordering.

I re-verified on the live front-end: the Query Loop collection post that previously rendered three cards (two leaked into the queried siblings) now renders exactly one, with the list-block post still rendering its items correctly. Full suite green (15 tests / 63 assertions). LGTM — thanks for the quick, thorough turnaround.

[github-actions]

Hey @adekbadek, good job getting this PR merged! 🎉

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