Backport block template resolution algorithm unit tests

tests/phpunit/data/themedir1/block-theme-child/block-templates/page-1.html

@@ -0,0 +1,3 @@
+<!-- wp:paragraph -->
+<p>Page (ID 1) Template</p>
+<!-- /wp:paragraph -->

tests/phpunit/data/themedir1/block-theme-child/page-home.php

@@ -0,0 +1,3 @@
+<?php
+
+echo 'PHP template for page with slug "home"';

tests/phpunit/data/themedir1/block-theme/block-templates/index.html

@@ -0,0 +1,3 @@
+<!-- wp:paragraph -->
+<p>Index Template</p>
+<!-- /wp:paragraph -->

tests/phpunit/data/themedir1/block-theme/block-templates/page-home.html

@@ -0,0 +1,3 @@
+<!-- wp:paragraph -->
+<p>Page (Home) Template</p>
+<!-- /wp:paragraph -->

tests/phpunit/data/themedir1/block-theme/block-templates/page.html

@@ -0,0 +1,3 @@
+<!-- wp:paragraph -->
+<p>Page Template</p>
+<!-- /wp:paragraph -->

tests/phpunit/data/themedir1/block-theme/page-1.php

@@ -0,0 +1,3 @@
+<?php
+
+echo 'PHP template for page with ID 1';

tests/phpunit/tests/block-template-utils.php

@@ -7,6 +7,8 @@
 
 /**
  * Tests for the Block Templates abstraction layer.
+ *
+ * @group block-templates
  */
 class Block_Template_Utils_Test extends WP_UnitTestCase {
 	private static $post;

tests/phpunit/tests/block-template.php

@@ -7,37 +7,128 @@
 
 /**
  * Tests for the block template loading algorithm.
+ *
+ * @group block-templates
  */
 class Block_Template_Test extends WP_UnitTestCase {
 	private static $post;
 
 	private static $template_canvas_path = ABSPATH . WPINC . '/template-canvas.php';
 
-	public static function wpSetUpBeforeClass() {
-		// Set up custom template post.
-		$args       = array(
-			'post_type'    => 'wp_template',
-			'post_name'    => 'wp-custom-template-my-block-template',
-			'post_title'   => 'My Custom Block Template',
-			'post_content' => 'Content',
-			'post_excerpt' => 'Description of my block template',
-			'tax_input'    => array(
-				'wp_theme' => array(
-					get_stylesheet(),
-				),
-			),
+	public function set_up() {
+		parent::set_up();
+		switch_theme( 'block-theme' );
+	}
+
+	public function tear_down() {
+		global $_wp_current_template_content;
+		unset( $_wp_current_template_content );
+
+		parent::tear_down();
+	}
+
+	function test_page_home_block_template_takes_precedence_over_less_specific_block_templates() {
+		global $_wp_current_template_content;
+		$type                   = 'page';
+		$templates              = array(
+			'page-home.php',
+			'page-1.php',
+			'page.php',
 		);
-		self::$post = self::factory()->post->create_and_get( $args );
-		wp_set_post_terms( self::$post->ID, get_stylesheet(), 'wp_theme' );
+		$resolved_template_path = locate_block_template( get_stylesheet_directory() . '/page-home.php', $type, $templates );
+		$this->assertEquals( self::$template_canvas_path, $resolved_template_path );
+		$this->assertStringEqualsFile( get_stylesheet_directory() . '/block-templates/page-home.html', $_wp_current_template_content );
 	}
 
-	public static function wpTearDownAfterClass() {
-		wp_delete_post( self::$post->ID );
+	function test_page_block_template_takes_precedence() {
+		global $_wp_current_template_content;
+		$type                   = 'page';
+		$templates              = array(
+			'page-slug-doesnt-exist.php',
+			'page-1.php',
+			'page.php',
+		);
+		$resolved_template_path = locate_block_template( get_stylesheet_directory() . '/page.php', $type, $templates );
+		$this->assertEquals( self::$template_canvas_path, $resolved_template_path );
+		$this->assertStringEqualsFile( get_stylesheet_directory() . '/block-templates/page.html', $_wp_current_template_content );
 	}
 
-	public function tear_down() {
+	function test_block_template_takes_precedence_over_equally_specific_php_template() {
 		global $_wp_current_template_content;
-		unset( $_wp_current_template_content );
+		$type                   = 'index';
+		$templates              = array(
+			'index.php',
+		);
+		$resolved_template_path = locate_block_template( get_stylesheet_directory() . '/index.php', $type, $templates );
+		$this->assertEquals( self::$template_canvas_path, $resolved_template_path );
+		$this->assertStringEqualsFile( get_stylesheet_directory() . '/block-templates/index.html', $_wp_current_template_content );
+	}
+
+	/**
+	 * In a hybrid theme, a PHP template of higher specificity will take precedence over a block template
+	 * with lower specificity.
+	 *
+	 * Covers https://github.com/WordPress/gutenberg/pull/29026.
+	 */
+	function test_more_specific_php_template_takes_precedence_over_less_specific_block_template() {
+		$page_id_template       = 'page-1.php';
+		$page_id_template_path  = get_stylesheet_directory() . '/' . $page_id_template;
+		$type                   = 'page';
+		$templates              = array(
+			'page-slug-doesnt-exist.php',
+			'page-1.php',
+			'page.php',
+		);
+		$resolved_template_path = locate_block_template( $page_id_template_path, $type, $templates );
+		$this->assertEquals( $page_id_template_path, $resolved_template_path );
+	}
+
+	/**
+	 * If a theme is a child of a block-based parent theme but has php templates for some of its pages,
+	 * a php template of the child will take precedence over the parent's block template if they have
+	 * otherwise equal specificity.
+	 *
+	 * Covers https://github.com/WordPress/gutenberg/pull/31123.
+	 *
+	 */
+	function test_child_theme_php_template_takes_precedence_over_equally_specific_parent_theme_block_template() {
+		/**
+		 * @todo This test is currently marked as skipped, since it wouldn't pass. Turns out that in Gutenberg,
+		 * it only passed due to a erroneous test setup.
+		 * For details, see https://github.com/WordPress/wordpress-develop/pull/1920#issuecomment-975929818.
+		 */
+		$this->markTestSkipped( 'The block template resolution algorithm needs fixing in order for this test to pass.' );
+
+		switch_theme( 'block-theme-child' );
+
+		$page_slug_template      = 'page-home.php';
+		$page_slug_template_path = get_stylesheet_directory() . '/' . $page_slug_template;
+		$type                    = 'page';
+		$templates               = array(
+			'page-home.php',
+			'page-1.php',
+			'page.php',
+		);
+		$resolved_template_path  = locate_block_template( $page_slug_template_path, $type, $templates );
+		$this->assertEquals( $page_slug_template_path, $resolved_template_path );
+	}
+
+	function test_child_theme_block_template_takes_precedence_over_equally_specific_parent_theme_php_template() {
+		global $_wp_current_template_content;
+
+		switch_theme( 'block-theme-child' );
+
+		$page_template                   = 'page-1.php';
+		$parent_theme_page_template_path = get_template_directory() . '/' . $page_template;
+		$type                            = 'page';
+		$templates                       = array(
+			'page-slug-doesnt-exist.php',
+			'page-1.php',
+			'page.php',
+		);
+		$resolved_template_path          = locate_block_template( $parent_theme_page_template_path, $type, $templates );
+		$this->assertEquals( self::$template_canvas_path, $resolved_template_path );
+		$this->assertStringEqualsFile( get_stylesheet_directory() . '/block-templates/page-1.html', $_wp_current_template_content );
 	}
 
 	/**
@@ -63,6 +154,22 @@ public function test_custom_page_php_template_takes_precedence_over_all_other_te
 	public function test_custom_page_block_template_takes_precedence_over_all_other_templates() {
 		global $_wp_current_template_content;
 
+		// Set up custom template post.
+		$args = array(
+			'post_type'    => 'wp_template',
+			'post_name'    => 'wp-custom-template-my-block-template',
+			'post_title'   => 'My Custom Block Template',
+			'post_content' => 'Content',
+			'post_excerpt' => 'Description of my block template',
+			'tax_input'    => array(
+				'wp_theme' => array(
+					get_stylesheet(),
+				),
+			),
+		);
+		$post = self::factory()->post->create_and_get( $args );
+		wp_set_post_terms( $post->ID, get_stylesheet(), 'wp_theme' );
+
 		$custom_page_block_template = 'wp-custom-template-my-block-template';
 		$page_template_path         = get_stylesheet_directory() . '/' . 'page.php';
 		$type                       = 'page';
@@ -74,7 +181,9 @@ public function test_custom_page_block_template_takes_precedence_over_all_other_
 		);
 		$resolved_template_path     = locate_block_template( $page_template_path, $type, $templates );
 		$this->assertSame( self::$template_canvas_path, $resolved_template_path );
-		$this->assertSame( self::$post->post_content, $_wp_current_template_content );
+		$this->assertSame( $post->post_content, $_wp_current_template_content );
+
+		wp_delete_post( $post->ID );
 	}
 
 	/**