.../block/lib/Drupal/block/BlockViewBuilder.php    |   18 +-
 .../Drupal/block/Tests/BlockStorageUnitTest.php    |   54 +--
 .../Drupal/block/Tests/BlockViewBuilderTest.php    |  346 ++++++++++++++++++++
 .../tests/modules/block_test/block_test.module     |   28 ++
 .../block_test/Plugin/Block/TestCacheBlock.php     |   10 +-
 5 files changed, 390 insertions(+), 66 deletions(-)

diff --git a/core/modules/block/lib/Drupal/block/BlockViewBuilder.php b/core/modules/block/lib/Drupal/block/BlockViewBuilder.php
index 4ccfcf4..a6a925a 100644
--- a/core/modules/block/lib/Drupal/block/BlockViewBuilder.php
+++ b/core/modules/block/lib/Drupal/block/BlockViewBuilder.php
@@ -103,6 +103,11 @@ public function viewMultiple(array $entities = array(), $view_mode = 'full', $la
 
       // @todo Remove after fixing http://drupal.org/node/1989568.
       $build[$key]['#block'] = $entity;
+
+      // Don't run in ::buildBlock() to ensure cache keys can be altered. If an
+      // alter hook wants to modify the block contents, it can append another
+      // #pre_render hook.
+      $this->moduleHandler()->alter(array('block_view', "block_view_$base_id"), $build[$entity_id], $plugin);
     }
     return $build;
   }
@@ -114,12 +119,10 @@ public function viewMultiple(array $entities = array(), $view_mode = 'full', $la
    * - if there is no content, aborts rendering, and makes sure the block won't
    *   be rendered.
    * - if there is content, moves the contextual links from the block content to
-   *   the block itself, and invokes the alter hooks.
+   *   the block itself.
    */
   public function buildBlock($build) {
-    $plugin = $build['#block']->getPlugin();
-    $content = $plugin->build();
-
+    $content = $build['#block']->getPlugin()->build();
     if (!empty($content)) {
       // Place the $content returned by the block plugin into a 'content' child
       // element, as a way to allow the plugin to have complete control of its
@@ -138,18 +141,13 @@ public function buildBlock($build) {
         }
       }
       $build['content'] = $content;
-
-      $base_id = $plugin->getBasePluginId();
-      $this->moduleHandler()->alter(array('block_view', "block_view_$base_id"), $build, $plugin);
-
-      return $build;
     }
     else {
       // Abort rendering: render as the empty string and ensure this block is
       // render cached, so we can avoid the work of having to repeatedly
       // determine whether the block is empty. E.g. modifying or adding entities
       // could cause the block to no longer be empty.
-      return array(
+      $build = array(
         '#markup' => '',
         '#cache' => $build['#cache'],
       );
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php
index d95edca..6a5be54 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php
@@ -56,7 +56,6 @@ public function testBlockCRUD() {
     // Run each test method in the same installation.
     $this->createTests();
     $this->loadTests();
-    $this->renderTests();
     $this->deleteTests();
   }
 
@@ -115,7 +114,7 @@ protected function createTests() {
   }
 
   /**
-   * Tests the rendering of blocks.
+   * Tests the loading of blocks.
    */
   protected function loadTests() {
     $entity = $this->controller->load('test_block');
@@ -130,57 +129,6 @@ protected function loadTests() {
   }
 
   /**
-   * Tests the rendering of blocks.
-   */
-  protected function renderTests() {
-    // Test the rendering of a block.
-    $entity = entity_load('block', 'test_block');
-    $output = entity_view($entity, 'block');
-    $expected = array();
-    $expected[] = '<div class="block block-block-test" id="block-test-block">';
-    $expected[] = '  ';
-    $expected[] = '    ';
-    $expected[] = '';
-    $expected[] = '  <div class="content">';
-    $expected[] = '          ';
-    $expected[] = '      </div>';
-    $expected[] = '</div>';
-    $expected[] = '';
-    $expected_output = implode("\n", $expected);
-    $this->assertEqual(drupal_render($output), $expected_output);
-
-    // Reset the HTML IDs so that the next render is not affected.
-    drupal_static_reset('drupal_html_id');
-
-    // Test the rendering of a block with a given title.
-    $entity = $this->controller->create(array(
-      'id' => 'test_block2',
-      'theme' => 'stark',
-      'plugin' => 'test_html',
-      'settings' => array(
-        'label' => 'Powered by Bananas',
-      ),
-    ));
-    $entity->save();
-    $output = entity_view($entity, 'block');
-    $expected = array();
-    $expected[] = '<div class="block block-block-test" id="block-test-block2">';
-    $expected[] = '  ';
-    $expected[] = '      <h2>Powered by Bananas</h2>';
-    $expected[] = '    ';
-    $expected[] = '';
-    $expected[] = '  <div class="content">';
-    $expected[] = '          ';
-    $expected[] = '      </div>';
-    $expected[] = '</div>';
-    $expected[] = '';
-    $expected_output = implode("\n", $expected);
-    $this->assertEqual(drupal_render($output), $expected_output);
-    // Clean up this entity.
-    $entity->delete();
-  }
-
-  /**
    * Tests the deleting of blocks.
    */
   protected function deleteTests() {
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockViewBuilderTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockViewBuilderTest.php
new file mode 100644
index 0000000..aa7dd2e
--- /dev/null
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockViewBuilderTest.php
@@ -0,0 +1,346 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\block\Tests\BlockViewBuilderTest.
+ */
+
+namespace Drupal\block\Tests;
+
+use Drupal\Component\Utility\NestedArray;
+use Drupal\Core\Cache\UrlCacheContext;
+use Drupal\simpletest\DrupalUnitTestBase;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Tests the block view builder.
+ */
+class BlockViewBuilderTest extends DrupalUnitTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('block', 'block_test', 'system');
+
+  /**
+   * The block being tested.
+   *
+   * @var \Drupal\block\Entity\BlockInterface
+   */
+  protected $block;
+
+  /**
+   * The block storage controller.
+   *
+   * @var \Drupal\Core\Config\Entity\ConfigStorageControllerInterface
+   */
+  protected $controller;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'Block rendering',
+      'description' => 'Tests the block view builder.',
+      'group' => 'Block',
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+
+    $this->controller = $this->container
+      ->get('entity.manager')
+      ->getStorageController('block');
+
+    \Drupal::state()->set('block_test.content', 'Llamas &gt; unicorns!');
+
+    // Create a block with only required values.
+    $this->block = $this->controller->create(array(
+      'id' => 'test_block',
+      'theme' => 'stark',
+      'plugin' => 'test_cache',
+    ));
+    $this->block->save();
+
+    $this->container->get('cache.block')->deleteAll();
+  }
+
+  /**
+   * Tests the rendering of blocks.
+   */
+  public function testBasicRendering() {
+    \Drupal::state()->set('block_test.content', '');
+
+    $entity = $this->controller->create(array(
+      'id' => 'test_block1',
+      'theme' => 'stark',
+      'plugin' => 'test_html',
+    ));
+    $entity->save();
+
+    // Test the rendering of a block.
+    $entity = entity_load('block', 'test_block1');
+    $output = entity_view($entity, 'block');
+    $expected = array();
+    $expected[] = '<div class="block block-block-test" id="block-test-block1">';
+    $expected[] = '  ';
+    $expected[] = '    ';
+    $expected[] = '';
+    $expected[] = '  <div class="content">';
+    $expected[] = '          ';
+    $expected[] = '      </div>';
+    $expected[] = '</div>';
+    $expected[] = '';
+    $expected_output = implode("\n", $expected);
+    $this->assertEqual(drupal_render($output), $expected_output);
+
+    // Reset the HTML IDs so that the next render is not affected.
+    drupal_static_reset('drupal_html_id');
+
+    // Test the rendering of a block with a given title.
+    $entity = $this->controller->create(array(
+      'id' => 'test_block2',
+      'theme' => 'stark',
+      'plugin' => 'test_html',
+      'settings' => array(
+        'label' => 'Powered by Bananas',
+      ),
+    ));
+    $entity->save();
+    $output = entity_view($entity, 'block');
+    $expected = array();
+    $expected[] = '<div class="block block-block-test" id="block-test-block2">';
+    $expected[] = '  ';
+    $expected[] = '      <h2>Powered by Bananas</h2>';
+    $expected[] = '    ';
+    $expected[] = '';
+    $expected[] = '  <div class="content">';
+    $expected[] = '          ';
+    $expected[] = '      </div>';
+    $expected[] = '</div>';
+    $expected[] = '';
+    $expected_output = implode("\n", $expected);
+    $this->assertEqual(drupal_render($output), $expected_output);
+  }
+
+  /**
+   * Tests block render cache handling.
+   */
+  public function testBlockViewBuilderCache() {
+    // Verify cache handling for a non-empty block.
+    $this->verifyRenderCacheHandling();
+
+    // Create an empty block.
+    $this->block = $this->controller->create(array(
+      'id' => 'test_block',
+      'theme' => 'stark',
+      'plugin' => 'test_cache',
+    ));
+    $this->block->save();
+    \Drupal::state()->set('block_test.content', NULL);
+
+    // Verify cache handling for an empty block.
+    $this->verifyRenderCacheHandling();
+  }
+
+  /**
+   * Verifies render cache handling of the block being tested.
+   *
+   * @see ::testBlockViewBuilderCache()
+   */
+  protected function verifyRenderCacheHandling() {
+    // Force a request via GET so we can get drupal_render() cache working.
+    $request_method = \Drupal::request()->server->get('REQUEST_METHOD');
+    $this->container->get('request')->setMethod('GET');
+
+    // Test that entities with caching disabled do not generate a cache entry.
+    $build = $this->getBlockRenderArray();
+    $this->assertTrue(isset($build['#cache']) && array_keys($build['#cache']) == array('tags'), 'The render array element of uncacheable blocks is not cached, but does have cache tags set.');
+
+    // Enable block caching.
+    $this->setBlockCacheConfig(array(
+      'max_age' => 600,
+    ));
+
+    // Test that a cache entry is created.
+    $build = $this->getBlockRenderArray();
+    $cid = drupal_render_cid_create($build);
+    drupal_render($build);
+    $this->assertTrue($this->container->get('cache.block')->get($cid), 'The block render element has been cached.');
+
+    // Re-save the block and check that the cache entry has been deleted.
+    $this->block->save();
+    $this->assertFalse($this->container->get('cache.block')->get($cid), 'The block render cache entry has been cleared when the block was saved.');
+
+    // Rebuild the render array (creating a new cache entry in the process) and
+    // delete the block to check the cache entry is deleted.
+    unset($build['#printed']);
+    drupal_render($build);
+    $this->assertTrue($this->container->get('cache.block')->get($cid), 'The block render element has been cached.');
+    $this->block->delete();
+    $this->assertFalse($this->container->get('cache.block')->get($cid), 'The block render cache entry has been cleared when the block was deleted.');
+
+    // Restore the previous request method.
+    $this->container->get('request')->setMethod($request_method);
+  }
+
+  /**
+   * Tests block view altering.
+   */
+  public function testBlockViewBuilderAlter() {
+    // Establish baseline.
+    $build = $this->getBlockRenderArray();
+    $this->assertIdentical(drupal_render($build), 'Llamas &gt; unicorns!');
+
+    // Enable the block view alter hook that adds a suffix, for basic testing.
+    \Drupal::state()->set('block_test_view_alter_suffix', TRUE);
+
+    // Basic: non-empty block.
+    $build = $this->getBlockRenderArray();
+    $this->assertTrue(isset($build['#suffix']) && $build['#suffix'] === '<br>Goodbye!', 'A block with content is altered.');
+    $this->assertIdentical(drupal_render($build), 'Llamas &gt; unicorns!<br>Goodbye!');
+
+    // Basic: empty block.
+    \Drupal::state()->set('block_test.content', NULL);
+    $build = $this->getBlockRenderArray();
+    $this->assertTrue(isset($build['#suffix']) && $build['#suffix'] === '<br>Goodbye!', 'A block without content is altered.');
+    $this->assertIdentical(drupal_render($build), '<br>Goodbye!');
+
+    // Disable the block view alter hook that adds a suffix, for basic testing.
+    \Drupal::state()->set('block_test_view_alter_suffix', FALSE);
+
+    // Force a request via GET so we can get drupal_render() cache working.
+    $request_method = \Drupal::request()->server->get('REQUEST_METHOD');
+    $this->container->get('request')->setMethod('GET');
+
+    $default_keys = array('entity_view', 'block', 'test_block', 'en', 'cache_context.theme');
+    $default_tags = array('content' => TRUE, 'block_view' => TRUE, 'block' => array('test_block'), 'block_plugin' => array('test_cache'));
+
+    // Advanced: cached block, but an alter hook adds an additional cache key.
+    $this->setBlockCacheConfig(array(
+      'max_age' => 600,
+    ));
+    $alter_add_key = $this->randomName();
+    \Drupal::state()->set('block_test_view_alter_cache_key', $alter_add_key);
+    $expected_keys = array_merge($default_keys, array($alter_add_key));
+    $build = $this->getBlockRenderArray();
+    $this->assertIdentical($expected_keys, $build['#cache']['keys'], 'An altered cacheable block has the expected cache keys.');
+    $cid = drupal_render_cid_create(array('#cache' => array('keys' => $expected_keys)));
+    $this->assertIdentical(drupal_render($build), '');
+    $cache_entry = $this->container->get('cache.block')->get($cid);
+    $this->assertTrue($cache_entry, 'The block render element has been cached with the expected cache ID.');
+    $expected_flattened_tags = array('content:1', 'block_view:1', 'block:test_block', 'block_plugin:test_cache');
+    $this->assertIdentical($cache_entry->tags, array_combine($expected_flattened_tags, $expected_flattened_tags)); //, 'The block render element has been cached with the expected cache tags.');
+    $this->container->get('cache.block')->delete($cid);
+
+    // Advanced: cached block, but an alter hook adds an additional cache tag.
+    $alter_add_tag = $this->randomName();
+    \Drupal::state()->set('block_test_view_alter_cache_tag', $alter_add_tag);
+    $expected_tags = NestedArray::mergeDeep($default_tags, array($alter_add_tag => TRUE));
+    $build = $this->getBlockRenderArray();
+    $this->assertIdentical($expected_tags, $build['#cache']['tags'], 'An altered cacheable block has the expected cache tags.');
+    $cid = drupal_render_cid_create(array('#cache' => array('keys' => $expected_keys)));
+    $this->assertIdentical(drupal_render($build), '');
+    $cache_entry = $this->container->get('cache.block')->get($cid);
+    $this->assertTrue($cache_entry, 'The block render element has been cached with the expected cache ID.');
+    $expected_flattened_tags = array('content:1', 'block_view:1', 'block:test_block', 'block_plugin:test_cache', $alter_add_tag . ':1');
+    $this->assertIdentical($cache_entry->tags, array_combine($expected_flattened_tags, $expected_flattened_tags)); //, 'The block render element has been cached with the expected cache tags.');
+    $this->container->get('cache.block')->delete($cid);
+
+    // Advanced: cached block, but an alter hook adds a #pre_render callback to
+    // alter the eventual content.
+    \Drupal::state()->set('block_test_view_alter_append_pre_render_prefix', TRUE);
+    $build = $this->getBlockRenderArray();
+    $this->assertFalse(isset($build['#prefix']), 'The appended #pre_render callback has not yet run before calling drupal_render().');
+    $this->assertIdentical(drupal_render($build), 'Hiya!<br>');
+    $this->assertTrue(isset($build['#prefix']) && $build['#prefix'] === 'Hiya!<br>', 'A cached block without content is altered.');
+
+    // Restore the previous request method.
+    $this->container->get('request')->setMethod($request_method);
+  }
+
+  /**
+   * Tests block render cache handling with configurable cache contexts.
+   *
+   * This is only intended to test that an existing block can be configured with
+   * additional contexts, not to test that each context works correctly.
+   *
+   * @see \Drupal\block\Tests\BlockCacheTest
+   */
+  public function testBlockViewBuilderCacheContexts() {
+    // Force a request via GET so we can get drupal_render() cache working.
+    $request_method = \Drupal::request()->server->get('REQUEST_METHOD');
+    $this->container->get('request')->setMethod('GET');
+
+    // First: no cache context.
+    $this->setBlockCacheConfig(array(
+      'max_age' => 600,
+    ));
+    $build = $this->getBlockRenderArray();
+    $cid = drupal_render_cid_create($build);
+    drupal_render($build);
+    $this->assertTrue($this->container->get('cache.block', $cid), 'The block render element has been cached.');
+
+    // Second: the "per URL" cache context.
+    $this->setBlockCacheConfig(array(
+      'max_age' => 600,
+      'contexts' => array('cache_context.url'),
+    ));
+    $old_cid = $cid;
+    $build = $this->getBlockRenderArray();
+    $cid = drupal_render_cid_create($build);
+    drupal_render($build);
+    $this->assertTrue($this->container->get('cache.block', $cid), 'The block render element has been cached.');
+    $this->assertNotEqual($cid, $old_cid, 'The cache ID has changed.');
+
+    // Third: the same block configuration, but a different URL.
+    $original_url_cache_context = $this->container->get('cache_context.url');
+    $temp_context = new UrlCacheContext(Request::create('/foo'));
+    $this->container->set('cache_context.url', $temp_context);
+    $old_cid = $cid;
+    $build = $this->getBlockRenderArray();
+    $cid = drupal_render_cid_create($build);
+    drupal_render($build);
+    $this->assertTrue($this->container->get('cache.block', $cid), 'The block render element has been cached.');
+    $this->assertNotEqual($cid, $old_cid, 'The cache ID has changed.');
+    $this->container->set('cache_context.url', $original_url_cache_context);
+
+    // Restore the previous request method.
+    $this->container->get('request')->setMethod($request_method);
+  }
+
+  /**
+   * Sets the test block's cache configuration.
+   *
+   * @param array $cache_config
+   *   The desired cache configuration.
+   */
+  protected function setBlockCacheConfig(array $cache_config) {
+    $block = $this->block->getPlugin();
+    $block->setConfigurationValue('cache', $cache_config);
+    $this->block->save();
+  }
+
+  /**
+   * Get a fully built render array for a block.
+   *
+   * @return array
+   *   The render array.
+   */
+  protected function getBlockRenderArray() {
+    $build = $this->container->get('entity.manager')->getViewBuilder('block')->view($this->block, 'block');
+
+    // Mock the build array to not require the theme registry.
+    unset($build['#theme']);
+
+    return $build;
+  }
+
+}
diff --git a/core/modules/block/tests/modules/block_test/block_test.module b/core/modules/block/tests/modules/block_test/block_test.module
index 1530f2c..a527ae1 100644
--- a/core/modules/block/tests/modules/block_test/block_test.module
+++ b/core/modules/block/tests/modules/block_test/block_test.module
@@ -5,6 +5,8 @@
  *   Provide test blocks.
  */
 
+use Drupal\block\BlockPluginInterface;
+
 /**
  * Implements hook_block_alter().
  */
@@ -13,3 +15,29 @@ function block_test_block_alter(&$block_info) {
     $block_info['test_block_instantiation']['category'] = t('Custom category');
   }
 }
+
+/**
+ * Implements hook_block_view_BASE_BLOCK_ID_alter().
+ */
+function block_test_block_view_test_cache_alter(array &$build, BlockPluginInterface $block) {
+  if (\Drupal::state()->get('block_test_view_alter_suffix') !== NULL) {
+    $build['#suffix'] = '<br>Goodbye!';
+  }
+  if (\Drupal::state()->get('block_test_view_alter_cache_key') !== NULL) {
+    $build['#cache']['keys'][] = \Drupal::state()->get('block_test_view_alter_cache_key');
+  }
+  if (\Drupal::state()->get('block_test_view_alter_cache_tag') !== NULL) {
+    $build['#cache']['tags'][\Drupal::state()->get('block_test_view_alter_cache_tag')] = TRUE;
+  }
+  if (\Drupal::state()->get('block_test_view_alter_append_pre_render_prefix') !== NULL) {
+    $build['#pre_render'][] = 'block_test_pre_render_alter_content';
+  }
+}
+
+/**
+ * #pre_render callback for a block to alter its content.
+ */
+function block_test_pre_render_alter_content($build) {
+  $build['#prefix'] = 'Hiya!<br>';
+  return $build;
+}
diff --git a/core/modules/block/tests/modules/block_test/lib/Drupal/block_test/Plugin/Block/TestCacheBlock.php b/core/modules/block/tests/modules/block_test/lib/Drupal/block_test/Plugin/Block/TestCacheBlock.php
index 0216fa1..b6508a8 100644
--- a/core/modules/block/tests/modules/block_test/lib/Drupal/block_test/Plugin/Block/TestCacheBlock.php
+++ b/core/modules/block/tests/modules/block_test/lib/Drupal/block_test/Plugin/Block/TestCacheBlock.php
@@ -23,9 +23,13 @@ class TestCacheBlock extends BlockBase {
    * {@inheritdoc}
    */
   public function build() {
-    return array(
-      '#markup' => \Drupal::state()->get('block_test.content'),
-    );
+    $content = \Drupal::state()->get('block_test.content');
+
+    $build = array();
+    if (!empty($content)) {
+      $build['#markup'] = $content;
+    }
+    return $build;
   }
 
 }