Shortcode: Fix issue when no attributes are passed

includes/Shortcode/Stories_Shortcode.php

@@ -61,10 +61,10 @@ public function register(): void {
 	 *
 	 * @since 1.5.0
 	 *
-	 * @param array<string,string|int> $attrs Shortcode attributes.
+	 * @param array<string,string|int>|string $attrs Shortcode attributes.
 	 * @return string Story markup.
 	 */
-	public function render_stories( array $attrs ): string {
+	public function render_stories( $attrs ): string {
 		$default_pairs = [
 			'view'               => 'circles',
 			'number_of_columns'  => 1,
@@ -89,6 +89,11 @@ public function render_stories( array $attrs ): string {
 			$default_pairs[ $taxonomy ] = '';
 		}
 
+		// Initialize '$attrs' when not an array OR is an empty string.
+		if ( empty( $attrs ) || ! \is_array( $attrs ) ) {
+			$attrs = [];
+		}
+
 		$attributes = shortcode_atts(
 			$default_pairs,
 			$attrs,

tests/phpunit/integration/tests/Shortcode/Stories_Shortcode.php

@@ -87,6 +87,20 @@ public function test_render_circles_view_in_shortcode(): void {
 		$this->assertNotSame( false, strpos( $actual, 'is-view-type-circles' ) );
 	}
 
+	/**
+	 * Should not fail on empty/blank string attribute.
+	 *
+	 * @covers ::render_stories
+	 * @covers ::prepare_story_attrs
+	 * @covers ::prepare_story_args
+	 */
+	public function test_empty_attribute_in_shortcode(): void {
+		$stories_shortcode = new Testee();
+		$actual            = $stories_shortcode->render_stories( '' );
+
+		$this->assertTrue( strpos( $actual, 'web-stories-list' ) > -1 );
+	}
+
 	/**
 	 * Stories should not be greater than 100.
 	 *