Fix issue with papi_get_page_type_id and only page type filter

src/lib/page.php

@@ -302,6 +302,16 @@ function papi_get_page_type_id( $post_id = 0 ) {
 		$page_type  = empty( $meta_value ) ? '' : $meta_value;
 	}
 
+	// When using `only_page_type` filter we need to fetch the value since it
+	// maybe not always saved in the database.
+	if ( empty ( $page_type ) ) {
+		$post_type = get_post_type( $post_id );
+
+		if ( is_string( $post_type ) && $page_type = papi_filter_settings_only_page_type( $post_type ) ) {
+			return $page_type;
+		}
+	}
+
 	// Load page type id from the container if it exists or
 	// load it from `papi_get_all_page_types`.
 	if ( empty( $page_type ) ) {

tests/cases/lib/page-test.php

@@ -260,6 +260,21 @@ public function test_papi_get_page_type_id() {
 		unset( $_GET['post_type'] );
 	}
 
+	public function test_papi_get_page_type_id_only_page_type_filter() {
+		$this->assertEmpty( papi_get_page_type_id() );
+
+		$_GET['post'] = $this->factory->post->create( ['post_type' => 'module'] );
+		$_GET['post_type'] = 'module';
+
+		add_filter( 'papi/settings/only_page_type_module', function () {
+			return 'modules/feature-module-type';
+		} );
+
+		$this->assertSame( 'modules/feature-module-type', papi_get_page_type_id() );
+		unset( $_GET['post'] );
+		unset( $_GET['post_type'] );
+	}
+
 	public function test_papi_get_post_types() {
 		$actual = papi_get_post_types();