Revision policy

Choose which revision of a page NeoWiki publishes: to the graph stores, the RDF export, the Subject reads GET /neowiki/v0/subject/{subjectId} and .../referencingSubjects, and its own Schema, Layout, Mapping and configuration reads. Without a policy every page publishes its latest revision.

class ApprovalRevisionPolicy implements RevisionPolicy {

	public function publishedRevision( RevisionRecord $revision ): ?RevisionRecord {
		return $this->approvalLookup->lastApprovedRevisionOf( $revision->getPage() );
	}

	public function revisionIsReadableBy( RevisionRecord $revision, Authority $viewer ): bool {
		return $this->approvalLookup->isApproved( $revision ) || $viewer->isAllowed( 'myext-see-drafts' );
	}

}

Register with NeoWikiRegistrar::setRevisionPolicy(); a second policy is refused with a warning on the NeoWiki log channel.

• publishedRevision() receives the page's current revision and returns the one to publish, of the same page, or null, which deletes the page's Page node and Subjects from the graph stores, makes the RDF export and the Subject reads answer not-found for it, and leaves its Subjects out of every referencing list. A policy that throws counts as returning null, with the error logged. It runs on every page save and rebuild and on every read above, so keep it cheap.
• revisionIsReadableBy() is asked when a REST caller names a revisionId or asks for latest (REST API); a refusal answers exactly like a revision that does not exist.

Approval changes outside an edit reach NeoWiki only through rebuild(), and a newly registered policy reaches the graph stores only through a full rebuild.

Editing reads the latest revision. So do ?action=subjects, GET /neowiki/v0/page/{pageId}/subjects, GET /neowiki/v0/page/{pageId}/mainSubject, the referenced Subjects on a revisionId read (#1390), the parse-time accessors, and the wiki's search index, which holds a page's Subjects the way MediaWiki holds its wikitext. Schema and Mapping reads are cached under the latest revision id, so an approval change without an edit to that Schema or Mapping page takes effect on its next edit or when the entry expires (#1392).