Federate comments only when the parent post is federated

[pfefferle]

Proposed changes:

Comments are now federated only when their parent post is federated.

Previously, Comment::should_be_federated() decided whether to federate a comment based on the comment author alone, without considering the parent post. This change adds a parent-post check so a brand-new comment is federated only when the post it belongs to is itself federated.

• Adds is_post_federated() in includes/functions-post.php: a post is federated when its stored federation state is federated and it is still publicly queryable (is_post_publicly_queryable() — post type enabled for ActivityPub, public status, not password-protected, allowed content visibility, and respecting the activitypub_is_post_publicly_queryable filter).
• Comment::should_be_federated() now gates brand-new comments on is_post_federated(). Comments that were already sent (was_sent()) are unaffected, so their Update and Delete activities continue to federate and keep remote copies in sync.

Combining the stored state with the live queryability check means a federated state left over from a later visibility or status change does not cause a comment to be federated.

Other information:

• Have you written new tests for your changes, if applicable?

Testing instructions:

• Create a post that is federated, add an approved comment from an ActivityPub-enabled user, and confirm a Create is added to the outbox as before.
• Set a post to a private status (or local content visibility), add an approved comment from an ActivityPub-enabled user, and confirm no comment activity is added to the outbox.
• Confirm an already-federated comment still produces Update/Delete activities after its parent post changes status.
• npm run env-test -- --filter='Test_Comment|Test_Functions_Post' — all green.

Changelog entry

A changelog entry is included in this PR (.github/changelog/fix-comment-federation-parent-state), so the automatic entry box is left unchecked.

[Copilot]

Pull request overview

This PR tightens comment federation so newly-created comments are only federated when their parent post is truly federated (stored state is federated and the post is still publicly queryable), preventing leakage of replies on private/local/unsupported content while preserving Update/Delete federation for comments that were already sent.

Changes:

• Added Activitypub\is_post_federated() to combine stored federation state with live public-queryability checks.
• Updated Comment::should_be_federated() to gate new comments on the parent post being federated (while allowing already-sent comments through).
• Added/updated PHPUnit coverage for the new helper and the new comment-federation behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/phpunit/tests/includes/scheduler/class-test-comment.php	Adjusts scheduler tests to ensure the parent post is marked federated for comment scheduling scenarios.
tests/phpunit/tests/includes/class-test-functions-post.php	Adds unit tests for is_post_federated() across multiple post visibility/state scenarios.
tests/phpunit/tests/includes/class-test-comment.php	Adds regression tests ensuring comments aren’t federated when the parent post was never federated, plus coverage for already-sent comments.
includes/functions-post.php	Introduces is_post_federated() helper combining object state and public-queryability.
includes/class-comment.php	Updates should_be_federated() to block new comments when the parent post isn’t federated.
.github/changelog/fix-comment-federation-parent-state	Adds a security changelog entry describing the tightened comment federation behavior.

[pfefferle]

Thanks @copilot — both addressed in 506e674:

1. Data-provider null static — self::$comment_post_ID is now initialized to 0. PHPUnit evaluates data providers before set_up(), so a null static made isset() false and the substitution in test_no_activity_scheduled() silently skipped, building comments with an invalid post ID. Initializing to 0 keeps the provider output non-null so the substitution picks up the real federated post assigned in set_up().
2. Filter cleanup on failure — the activitypub_is_post_publicly_queryable filter add/assert/remove is now wrapped in try/finally, so the filter cannot leak into subsequent tests if the assertion fails.

CI remains green across PHP 7.4 / 8.3 / 8.5.