refactor: Revert filter consolidation into wp_get_media_library_attachment_months()

Move the media_library_months_with_files filter back to the
two call sites (wp_enqueue_media and media_upload_library_form)
where it originally lived. Simplify the function to just the
raw query without transient caching or int casting. Remove the
now-unnecessary transient invalidation from clean_post_cache().
Update tests to match.

Author: apermo

src/wp-admin/includes/media.php

@@ -2852,7 +2852,11 @@ function media_upload_library_form( $errors ) {
 
 	<div class="alignleft actions">
 		<?php
-		$months = wp_get_media_library_attachment_months();
+		/** This filter is documented in wp-includes/media.php */
+		$months = apply_filters( 'media_library_months_with_files', null );
+		if ( ! is_array( $months ) ) {
+			$months = wp_get_media_library_attachment_months();
+		}
 
 		$month_count    = count( $months );
 		$selected_month = isset( $_GET['m'] ) ? (int) $_GET['m'] : 0;

src/wp-includes/media.php

@@ -4866,7 +4866,25 @@ function wp_enqueue_media( $args = array() ) {
 		);
 	}
 
-	$months = wp_get_media_library_attachment_months();
+	/**
+	 * Allows overriding the list of months displayed in the media library.
+	 *
+	 * By default (if this filter does not return an array), a query will be
+	 * run to determine the months that have media items.  This query can be
+	 * expensive for large media libraries, so it may be desirable for sites to
+	 * override this behavior.
+	 *
+	 * @since 4.7.4
+	 *
+	 * @link https://core.trac.wordpress.org/ticket/31071
+	 *
+	 * @param stdClass[]|null $months An array of objects with `month` and `year`
+	 *                                properties, or `null` for default behavior.
+	 */
+	$months = apply_filters( 'media_library_months_with_files', null );
+	if ( ! is_array( $months ) ) {
+		$months = wp_get_media_library_attachment_months();
+	}
 
 	foreach ( $months as $month_year ) {
 		$month_year->text = sprintf(
@@ -5137,44 +5155,20 @@ function wp_enqueue_media( $args = array() ) {
  *
  *     $months = wp_get_media_library_attachment_months();
  *     $months === array(
- *         (object) array( 'year' => 2025, 'month' => 2 ),
- *         (object) array( 'year' => 2024, 'month' => 11 ),
+ *         (object) array( 'year' => '2025', 'month' => '2' ),
+ *         (object) array( 'year' => '2024', 'month' => '11' ),
  *     );
  *
  * @since tbd
  *
  * @global wpdb $wpdb WordPress database abstraction object.
  *
- * @return array<int, object{year: int, month: int}> Months with associated attachment post dates.
+ * @return array<int, object{year: string, month: string}> Months with associated attachment post dates.
  */
 function wp_get_media_library_attachment_months(): array {
 	global $wpdb;
 
-	/**
-	 * Allows overriding the list of months displayed in the media library.
-	 *
-	 * Returning an array from this filter will bypass both the transient cache
-	 * and the database query.
-	 *
-	 * @since 4.7.4
-	 * @since tbd Moved to {@see wp_get_media_library_attachment_months()}.
-	 *
-	 * @link https://core.trac.wordpress.org/ticket/31071
-	 *
-	 * @param stdClass[]|null $months An array of objects with `year` and `month`
-	 *                                properties, or `null` for default behavior.
-	 */
-	$months = apply_filters( 'media_library_months_with_files', null );
-	if ( is_array( $months ) ) {
-		return $months;
-	}
-
-	$months = get_transient( 'wp_media_library_attachment_months' );
-	if ( false !== $months ) {
-		return $months;
-	}
-
-	$months = $wpdb->get_results(
+	return $wpdb->get_results(
 		$wpdb->prepare(
 			"SELECT DISTINCT YEAR( post_date ) AS year, MONTH( post_date ) AS month
 				FROM $wpdb->posts
@@ -5183,15 +5177,6 @@ function wp_get_media_library_attachment_months(): array {
 			'attachment'
 		)
 	);
-
-	foreach ( $months as $row ) {
-		$row->year  = (int) $row->year;
-		$row->month = (int) $row->month;
-	}
-
-	set_transient( 'wp_media_library_attachment_months', $months, WEEK_IN_SECONDS );
-
-	return $months;
 }
 
 /**

src/wp-includes/post.php

@@ -7791,10 +7791,6 @@ function clean_post_cache( $post ) {
 		do_action( 'clean_page_cache', $post->ID );
 	}
 
-	if ( 'attachment' === $post->post_type ) {
-		delete_transient( 'wp_media_library_attachment_months' );
-	}
-
 	wp_cache_set_posts_last_changed();
 }
 

tests/phpunit/tests/media/wpGetMediaLibraryAttachmentMonths.php

@@ -9,11 +9,11 @@
 class Tests_Media_wpGetMediaLibraryAttachmentMonths extends WP_UnitTestCase {
 
 	/**
-	 * Tests that the function returns the correct months and caches the result.
+	 * Tests that the function returns the correct months.
 	 *
 	 * @ticket 63279
 	 */
-	public function test_returns_months_and_caches_result() {
+	public function test_returns_months() {
 		self::factory()->post->create(
 			array(
 				'post_type' => 'attachment',
@@ -27,69 +27,12 @@ public function test_returns_months_and_caches_result() {
 			)
 		);
 
-		delete_transient( 'wp_media_library_attachment_months' );
-
 		$months = wp_get_media_library_attachment_months();
 
 		$this->assertCount( 2, $months );
-		$this->assertSame( 2025, $months[0]->year );
-		$this->assertSame( 3, $months[0]->month );
-		$this->assertSame( 2024, $months[1]->year );
-		$this->assertSame( 11, $months[1]->month );
-
-		// Verify the result was cached.
-		$this->assertEquals( $months, get_transient( 'wp_media_library_attachment_months' ) );
-	}
-
-	/**
-	 * Tests that the filter bypasses transient and query.
-	 *
-	 * @ticket 63279
-	 */
-	public function test_filter_overrides_result() {
-		self::factory()->post->create(
-			array(
-				'post_type' => 'attachment',
-				'post_date' => '2025-06-01 00:00:00',
-			)
-		);
-
-		delete_transient( 'wp_media_library_attachment_months' );
-
-		// Confirm the function returns data without the filter.
-		$this->assertNotEmpty( wp_get_media_library_attachment_months() );
-
-		delete_transient( 'wp_media_library_attachment_months' );
-
-		$override = array(
-			(object) array(
-				'year'  => 2020,
-				'month' => 1,
-			),
-		);
-
-		add_filter(
-			'media_library_months_with_files',
-			static function () use ( $override ) {
-				return $override;
-			}
-		);
-
-		$months = wp_get_media_library_attachment_months();
-
-		$this->assertSame( $override, $months );
-	}
-
-	/**
-	 * Tests that the transient is deleted when a new attachment is created.
-	 *
-	 * @ticket 63279
-	 */
-	public function test_transient_is_invalidated_on_new_attachment() {
-		set_transient( 'wp_media_library_attachment_months', array() );
-
-		self::factory()->post->create( array( 'post_type' => 'attachment' ) );
-
-		$this->assertFalse( get_transient( 'wp_media_library_attachment_months' ) );
+		$this->assertSame( '2025', $months[0]->year );
+		$this->assertSame( '3', $months[0]->month );
+		$this->assertSame( '2024', $months[1]->year );
+		$this->assertSame( '11', $months[1]->month );
 	}
 }