Taxonomy: Add UI to Category page to indicate default category

src/wp-admin/edit-tags.php

@@ -627,12 +627,40 @@
 <div class="form-wrap edit-term-notes">
 <p>
 	<?php
+	$default_category_id = (int) get_option( 'default_category' );
 	printf(
-		/* translators: %s: Default category. */
+		/* translators: %s: Default category name. */
 		__( 'Deleting a category does not delete the posts in that category. Instead, posts that were only assigned to the deleted category are set to the default category %s. The default category cannot be deleted.' ),
 		/** This filter is documented in wp-includes/category-template.php */
-		'<strong>' . apply_filters( 'the_category', get_cat_name( get_option( 'default_category' ) ), '', '' ) . '</strong>'
+		'<strong>' . apply_filters( 'the_category', get_cat_name( $default_category_id ), '', '' ) . '</strong>'
 	);
+
+	$default_edit_link  = current_user_can( 'edit_term', $default_category_id ) ? get_edit_term_link( $default_category_id, 'category' ) : null;
+	$can_change_default = current_user_can( 'manage_options' );
+
+	if ( $default_edit_link && $can_change_default ) {
+		echo ' ';
+		printf(
+			/* translators: 1: URL to edit the default category, 2: URL to Writing Settings. */
+			__( 'It can be <a href="%1$s">renamed</a> or you can choose a <a href="%2$s">different default category</a>.' ),
+			esc_url( $default_edit_link ),
+			esc_url( admin_url( 'options-writing.php#default_category' ) )
+		);
+	} elseif ( $default_edit_link ) {
+		echo ' ';
+		printf(
+			/* translators: %s: URL to edit the default category. */
+			__( 'It can be <a href="%s">renamed</a>.' ),
+			esc_url( $default_edit_link )
+		);
+	} elseif ( $can_change_default ) {
+		echo ' ';
+		printf(
+			/* translators: %s: URL to Writing Settings. */
+			__( 'You can choose a <a href="%s">different default category</a>.' ),
+			esc_url( admin_url( 'options-writing.php#default_category' ) )
+		);
+	}
 	?>
 </p>
 	<?php if ( current_user_can( 'import' ) ) : ?>

src/wp-admin/includes/class-wp-terms-list-table.php

@@ -383,6 +383,13 @@ public function column_cb( $item ) {
 	public function column_name( $tag ) {
 		$taxonomy = $this->screen->taxonomy;
 
+		$default_term_label = '';
+		if ( (int) get_option( 'default_' . $taxonomy ) === $tag->term_id
+			|| (int) get_option( 'default_term_' . $taxonomy ) === $tag->term_id
+		) {
+			$default_term_label = ' &mdash; <span class="taxonomy-default-label">' . __( 'Default' ) . '</span>';
+		}
+
 		$pad = str_repeat( '&#8212; ', max( 0, $this->level ) );
 
 		/**
@@ -420,8 +427,9 @@ public function column_name( $tag ) {
 		}
 
 		$output = sprintf(
-			'<strong>%s</strong><br />',
-			$name
+			'<strong>%s%s</strong><br />',
+			$name,
+			$default_term_label
 		);
 
 		/** This filter is documented in wp-admin/includes/class-wp-terms-list-table.php */
@@ -530,6 +538,19 @@ protected function handle_row_actions( $item, $column_name, $primary ) {
 			);
 		}
 
+		if ( 'category' === $taxonomy
+			&& (int) get_option( 'default_category' ) === $tag->term_id
+			&& current_user_can( 'manage_options' )
+		) {
+			$actions['change-default'] = sprintf(
+				'<a href="%s" aria-label="%s">%s</a>',
+				esc_url( admin_url( 'options-writing.php#default_category' ) ),
+				/* translators: %s: Taxonomy term name. */
+				esc_attr( sprintf( __( 'Change the default category from &#8220;%s&#8221;' ), $tag->name ) ),
+				__( 'Change Default' )
+			);
+		}
+
 		/**
 		 * Filters the action links displayed for each term in the Tags list table.
 		 *

tests/phpunit/tests/admin/wpTermsListTable.php

@@ -38,6 +38,17 @@ public function set_up() {
 		$this->terms_list_table = new WP_Terms_List_Table();
 	}
 
+	/**
+	 * Builds a terms list table bound to a specific taxonomy screen so that
+	 * `$this->screen->taxonomy` resolves correctly inside the table methods.
+	 *
+	 * @param string $taxonomy Taxonomy slug.
+	 * @return WP_Terms_List_Table
+	 */
+	private function get_terms_list_table_for_taxonomy( $taxonomy ) {
+		return new WP_Terms_List_Table( array( 'screen' => 'edit-' . $taxonomy ) );
+	}
+
 	/**
 	 * Call an inaccessible (private or protected) method.
 	 *
@@ -87,4 +98,144 @@ public function test_handle_row_actions_as_admin() {
 		$this->assertStringContainsString( 'Delete', $actions, 'Delete action should be displayed to the admin.' );
 		$this->assertStringContainsString( admin_url( 'term.php' ), $actions, 'Edit term link should be displayed to the admin.' );
 	}
+
+	/**
+	 * @covers WP_Terms_List_Table::handle_row_actions()
+	 *
+	 * @ticket 26268
+	 */
+	public function test_change_default_action_shown_for_default_category_as_admin() {
+		wp_set_current_user( self::$admin_id );
+
+		$default_category = self::factory()->term->create_and_get( array( 'taxonomy' => self::CATEGORY_TAXONOMY ) );
+		$previous_default = get_option( 'default_category' );
+		update_option( 'default_category', $default_category->term_id );
+
+		$list_table = $this->get_terms_list_table_for_taxonomy( self::CATEGORY_TAXONOMY );
+		$actions    = $this->call_inaccessible_method( $list_table, 'handle_row_actions', array( $default_category, 'title', 'title' ) );
+
+		update_option( 'default_category', $previous_default );
+
+		$this->assertStringContainsString( 'change-default', $actions, 'Change Default action should be displayed for the default category.' );
+		$this->assertStringContainsString( esc_url( admin_url( 'options-writing.php#default_category' ) ), $actions, 'Change Default link should target the Writing Settings field.' );
+	}
+
+	/**
+	 * @covers WP_Terms_List_Table::handle_row_actions()
+	 *
+	 * @ticket 26268
+	 */
+	public function test_change_default_action_hidden_for_default_category_as_author() {
+		wp_set_current_user( self::$author_id );
+
+		$default_category = self::factory()->term->create_and_get( array( 'taxonomy' => self::CATEGORY_TAXONOMY ) );
+		$previous_default = get_option( 'default_category' );
+		update_option( 'default_category', $default_category->term_id );
+
+		$list_table = $this->get_terms_list_table_for_taxonomy( self::CATEGORY_TAXONOMY );
+		$actions    = $this->call_inaccessible_method( $list_table, 'handle_row_actions', array( $default_category, 'title', 'title' ) );
+
+		update_option( 'default_category', $previous_default );
+
+		$this->assertStringNotContainsString( 'change-default', $actions, 'Change Default action should be hidden for users without manage_options.' );
+	}
+
+	/**
+	 * @covers WP_Terms_List_Table::handle_row_actions()
+	 *
+	 * @ticket 26268
+	 */
+	public function test_change_default_action_hidden_for_non_default_category() {
+		wp_set_current_user( self::$admin_id );
+
+		$default_category     = self::factory()->term->create_and_get( array( 'taxonomy' => self::CATEGORY_TAXONOMY ) );
+		$non_default_category = self::factory()->term->create_and_get( array( 'taxonomy' => self::CATEGORY_TAXONOMY ) );
+		$previous_default     = get_option( 'default_category' );
+		update_option( 'default_category', $default_category->term_id );
+
+		$list_table = $this->get_terms_list_table_for_taxonomy( self::CATEGORY_TAXONOMY );
+		$actions    = $this->call_inaccessible_method( $list_table, 'handle_row_actions', array( $non_default_category, 'title', 'title' ) );
+
+		update_option( 'default_category', $previous_default );
+
+		$this->assertStringNotContainsString( 'change-default', $actions, 'Change Default action should only appear on the default category row.' );
+	}
+
+	/**
+	 * @covers WP_Terms_List_Table::handle_row_actions()
+	 *
+	 * @ticket 26268
+	 */
+	public function test_change_default_action_hidden_for_non_category_taxonomy() {
+		wp_set_current_user( self::$admin_id );
+
+		$tag              = self::factory()->term->create_and_get( array( 'taxonomy' => 'post_tag' ) );
+		$previous_default = get_option( 'default_category' );
+		// Match the term ID so only the taxonomy check can suppress the action.
+		update_option( 'default_category', $tag->term_id );
+
+		$list_table = $this->get_terms_list_table_for_taxonomy( 'post_tag' );
+		$actions    = $this->call_inaccessible_method( $list_table, 'handle_row_actions', array( $tag, 'title', 'title' ) );
+
+		update_option( 'default_category', $previous_default );
+
+		$this->assertStringNotContainsString( 'change-default', $actions, 'Change Default action should not appear on non-category taxonomies.' );
+	}
+
+	/**
+	 * @covers WP_Terms_List_Table::column_name()
+	 *
+	 * @ticket 26268
+	 */
+	public function test_column_name_shows_default_label_for_default_category() {
+		wp_set_current_user( self::$admin_id );
+
+		$default_category = self::factory()->term->create_and_get( array( 'taxonomy' => self::CATEGORY_TAXONOMY ) );
+		$previous_default = get_option( 'default_category' );
+		update_option( 'default_category', $default_category->term_id );
+
+		$list_table = $this->get_terms_list_table_for_taxonomy( self::CATEGORY_TAXONOMY );
+		$output     = $list_table->column_name( $default_category );
+
+		update_option( 'default_category', $previous_default );
+
+		$this->assertStringContainsString( 'taxonomy-default-label', $output, 'Default label markup should be rendered for the default category.' );
+	}
+
+	/**
+	 * @covers WP_Terms_List_Table::column_name()
+	 *
+	 * @ticket 26268
+	 */
+	public function test_column_name_shows_default_label_for_default_term_custom_taxonomy() {
+		wp_set_current_user( self::$admin_id );
+
+		register_taxonomy( 'wptest_default_label_tax', 'post' );
+		$default_term = self::factory()->term->create_and_get( array( 'taxonomy' => 'wptest_default_label_tax' ) );
+		update_option( 'default_term_wptest_default_label_tax', $default_term->term_id );
+
+		$list_table = $this->get_terms_list_table_for_taxonomy( 'wptest_default_label_tax' );
+		$output     = $list_table->column_name( $default_term );
+
+		delete_option( 'default_term_wptest_default_label_tax' );
+		unregister_taxonomy( 'wptest_default_label_tax' );
+
+		$this->assertStringContainsString( 'taxonomy-default-label', $output, 'Default label should appear for terms identified by default_term_{taxonomy}.' );
+	}
+
+	/**
+	 * @covers WP_Terms_List_Table::column_name()
+	 *
+	 * @ticket 26268
+	 */
+	public function test_column_name_omits_default_label_for_non_default_term() {
+		wp_set_current_user( self::$admin_id );
+
+		$non_default_category = self::factory()->term->create_and_get( array( 'taxonomy' => self::CATEGORY_TAXONOMY ) );
+
+		$list_table = $this->get_terms_list_table_for_taxonomy( self::CATEGORY_TAXONOMY );
+		$output     = $list_table->column_name( $non_default_category );
+
+		$this->assertStringNotContainsString( 'taxonomy-default-label', $output, 'Default label should not appear on non-default terms.' );
+	}
 }