core/includes/common.inc                           | 22 +++--
 .../system/src/Tests/Common/PageRenderTest.php     | 95 ++++++++++++++++++++++
 core/modules/system/system.module                  | 19 ++++-
 .../system/tests/modules/bc_test/bc_test.info.yml  |  6 ++
 .../system/tests/modules/bc_test/bc_test.module    | 44 ++++++++++
 .../tests/modules/common_test/common_test.module   | 38 +++++++++
 6 files changed, 213 insertions(+), 11 deletions(-)

diff --git a/core/includes/common.inc b/core/includes/common.inc
index 16b1194..3eb59df 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -2473,19 +2473,25 @@ function drupal_prepare_page($page) {
   }
 
   // Modules can add attachments.
-  $pseudo_page_for_attachments = [];
+  $attachments = [];
   foreach (\Drupal::moduleHandler()->getImplementations('page_attachments') as $module) {
     $function = $module . '_page_attachments';
-    $function($pseudo_page_for_attachments);
+    $function($attachments);
+  }
+  if (array_diff(array_keys($attachments), ['#attached', '#post_render_cache']) !== []) {
+    throw new \LogicException('Only #attached and #post_render_cache may be set in hook_page_attachments()');
   }
   // Modules and themes can alter page attachments.
-  \Drupal::moduleHandler()->alter('page_attachments', $pseudo_page_for_attachments);
-  \Drupal::theme()->alter('page_attachments', $pseudo_page_for_attachments);
-  if (isset($pseudo_page_for_attachments['#attached'])) {
-    $page['#attached'] = $pseudo_page_for_attachments['#attached'];
+  \Drupal::moduleHandler()->alter('page_attachments', $attachments);
+  \Drupal::theme()->alter('page_attachments', $attachments);
+  if (array_diff(array_keys($attachments), ['#attached', '#post_render_cache']) !== []) {
+    throw new \LogicException('Only #attached and #post_render_cache may be set in hook_page_attachments_alter()');
+  }
+  if (isset($attachments['#attached'])) {
+    $page['#attached'] = $attachments['#attached'];
   }
-  if (isset($pseudo_page_for_attachments['#post_render_cache'])) {
-    $page['#post_render_cache'] = $pseudo_page_for_attachments['#post_render_cache'];
+  if (isset($attachments['#post_render_cache'])) {
+    $page['#post_render_cache'] = $attachments['#post_render_cache'];
   }
 
   // Modules can add renderable arrays to the top and bottom of the page.
diff --git a/core/modules/system/src/Tests/Common/PageRenderTest.php b/core/modules/system/src/Tests/Common/PageRenderTest.php
new file mode 100644
index 0000000..cf8d848
--- /dev/null
+++ b/core/modules/system/src/Tests/Common/PageRenderTest.php
@@ -0,0 +1,95 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Common\PageRenderTest.
+ */
+
+namespace Drupal\system\Tests\Common;
+
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Test page rendering hooks.
+ *
+ * @group system
+ */
+class PageRenderTest extends KernelTestBase {
+
+  /**
+   * Tests hook_page_attachments() exceptions.
+   */
+  function testHookPageAttachmentsExceptions() {
+    $this->enableModules(['common_test']);
+    $this->assertPageRenderHookExceptions('common_test', 'hook_page_attachments');
+  }
+
+  /**
+   * Tests hook_page_attachments_alter() exceptions.
+   */
+  function testHookPageAlter() {
+    $this->enableModules(['common_test']);
+    $this->assertPageRenderHookExceptions('common_test', 'hook_page_attachments_alter');
+  }
+
+  /**
+   * Tests hook_page_build() exceptions, a deprecated hook kept around for BC.
+   */
+  function testHookPageBuildExceptions() {
+    // Also enable the system module, because that module invokes the BC hooks.
+    $this->enableModules(['bc_test', 'system']);
+    $this->assertPageRenderHookExceptions('bc_test', 'hook_page_build');
+  }
+
+  /**
+   * Tests hook_page_alter(), a deprecated hook kept around for BC.
+   */
+  function testHookPageAttachmentsAlter() {
+    // Also enable the system module, because that module invokes the BC hooks.
+    $this->enableModules(['bc_test', 'system']);
+    $this->assertPageRenderHookExceptions('bc_test', 'hook_page_alter');
+  }
+
+  /**
+   * Asserts whether expected exceptions are thrown for invalid hook implementations.
+   *
+   * @param string $module
+   *   The module whose invalid logic in its hooks to enable.
+   * @param string $hook
+   *   The page render hook to assert expected exceptions for.
+   */
+  function assertPageRenderHookExceptions($module, $hook) {
+    // Assert a valid hook implementation doesn't trigger an exception.
+    $page = [];
+    drupal_prepare_page($page);
+
+    // Assert an invalid hook implementation doesn't trigger an exception.
+    \Drupal::state()->set($module . '.' . $hook . '.descendant_attached', TRUE);
+    $assertion = $hook . '() implementation that sets #attached on a descendant triggers an exception';
+    $page = [];
+    try {
+      drupal_prepare_page($page);
+      $this->error($assertion);
+    }
+    catch (\LogicException $e) {
+      $this->pass($assertion);
+      $this->assertEqual($e->getMessage(), 'Only #attached and #post_render_cache may be set in ' . $hook . '()');
+    }
+    \Drupal::state()->set('bc_test.' . $hook . '.descendant_attached', FALSE);
+
+    // Assert an invalid hook implementation doesn't trigger an exception.
+    \Drupal::state()->set('bc_test.' . $hook . '.render_array', TRUE);
+    $assertion = $hook . '() implementation that sets a child render array triggers an exception';
+    $page = [];
+    try {
+      drupal_prepare_page($page);
+      $this->error($assertion);
+    }
+    catch (\LogicException $e) {
+      $this->pass($assertion);
+      $this->assertEqual($e->getMessage(), 'Only #attached and #post_render_cache may be set in ' . $hook . '()');
+    }
+    \Drupal::state()->set($module . '.' . $hook . '.render_array', FALSE);
+  }
+
+}
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 41ad2c0..d201cbe 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -587,12 +587,25 @@ function system_page_attachments(array &$page) {
 
   // Invoke hook_page_build() for modules and hook_page_alter() for both modules
   // and, for backwards compatibility.
+  $attachments = [];
   foreach (\Drupal::moduleHandler()->getImplementations('page_build') as $module) {
     $function = $module . '_page_build';
-    $function($page);
+    $function($attachments);
+  }
+  if (array_diff(array_keys($attachments), ['#attached', '#post_render_cache']) !== []) {
+    throw new \LogicException('Only #attached and #post_render_cache may be set in hook_page_build()');
+  }
+  \Drupal::moduleHandler()->alter('page', $attachments);
+  \Drupal::theme()->alter('page', $attachments);
+  if (array_diff(array_keys($attachments), ['#attached', '#post_render_cache']) !== []) {
+    throw new \LogicException('Only #attached and #post_render_cache may be set in hook_page_alter()');
+  }
+  if (isset($attachments['#attached'])) {
+    $page['#attached'] = $attachments['#attached'];
+  }
+  if (isset($attachments['#post_render_cache'])) {
+    $page['#post_render_cache'] = $attachments['#post_render_cache'];
   }
-  \Drupal::moduleHandler()->alter('page', $page);
-  \Drupal::theme()->alter('page', $page);
 }
 
 /**
diff --git a/core/modules/system/tests/modules/bc_test/bc_test.info.yml b/core/modules/system/tests/modules/bc_test/bc_test.info.yml
new file mode 100644
index 0000000..20dbd82
--- /dev/null
+++ b/core/modules/system/tests/modules/bc_test/bc_test.info.yml
@@ -0,0 +1,6 @@
+name: 'Backwards Compatibility Test'
+type: module
+description: 'Support module for backwards compatibility tests.'
+package: Testing
+version: VERSION
+core: 8.x
diff --git a/core/modules/system/tests/modules/bc_test/bc_test.module b/core/modules/system/tests/modules/bc_test/bc_test.module
new file mode 100644
index 0000000..537acb8
--- /dev/null
+++ b/core/modules/system/tests/modules/bc_test/bc_test.module
@@ -0,0 +1,44 @@
+<?php
+
+/**
+ * @file
+ * Helper module for backwards compatibility (BC) tests.
+ */
+
+/**
+ * Implements hook_page_build().
+ *
+ * @see \Drupal\system\Tests\Common\PageRenderTest::assertPageRenderHookExceptions()
+ */
+function bc_test_page_build(&$page) {
+  $page['#attached']['library'][] = 'core/jquery';
+
+  if (\Drupal::state()->get('bc_test.hook_page_build.descendant_attached', FALSE)) {
+    $page['content']['#attached']['library'][] = 'core/jquery';
+  }
+
+  if (\Drupal::state()->get('bc_test.hook_page_build.render_array', FALSE)) {
+    $page['something'] = [
+      '#markup' => 'test',
+    ];
+  }
+}
+
+/**
+ * Implements hook_page_alter().
+ *
+ * @see \Drupal\system\Tests\Common\PageRenderTest::assertPageRenderHookExceptions()
+ */
+function bc_test_page_alter(&$page) {
+  $page['#attached']['library'][] = 'core/jquery';
+
+  if (\Drupal::state()->get('bc_test.hook_page_alter.descendant_attached', FALSE)) {
+    $page['content']['#attached']['library'][] = 'core/jquery';
+  }
+
+  if (\Drupal::state()->get('bc_test.hook_page_alter.render_array', FALSE)) {
+    $page['something'] = [
+      '#markup' => 'test',
+    ];
+  }
+}
diff --git a/core/modules/system/tests/modules/common_test/common_test.module b/core/modules/system/tests/modules/common_test/common_test.module
index e812b61..a9de4cc 100644
--- a/core/modules/system/tests/modules/common_test/common_test.module
+++ b/core/modules/system/tests/modules/common_test/common_test.module
@@ -255,3 +255,41 @@ function common_test_post_render_cache_placeholder(array $element, array $contex
 
   return $element;
 }
+
+/**
+ * Implements hook_page_attachments().
+ *
+ * @see \Drupal\system\Tests\Common\PageRenderTest::assertPageRenderHookExceptions()
+ */
+function common_test_page_attachments(array &$page) {
+  $page['#attached']['library'][] = 'core/jquery';
+
+  if (\Drupal::state()->get('common_test.hook_page_attachments.descendant_attached', FALSE)) {
+    $page['content']['#attached']['library'][] = 'core/jquery';
+  }
+
+  if (\Drupal::state()->get('common_test.hook_page_attachments.render_array', FALSE)) {
+    $page['something'] = [
+      '#markup' => 'test',
+    ];
+  }
+}
+
+/**
+ * Implements hook_page_attachments_alter().
+ *
+ * @see \Drupal\system\Tests\Common\PageRenderTest::assertPageRenderHookExceptions()
+ */
+function common_test_page_attachments_alter(array &$page) {
+  $page['#attached']['library'][] = 'core/jquery';
+
+  if (\Drupal::state()->get('common_test.hook_page_attachments_alter.descendant_attached', FALSE)) {
+    $page['content']['#attached']['library'][] = 'core/jquery';
+  }
+
+  if (\Drupal::state()->get('common_test.hook_page_attachments_alter.render_array', FALSE)) {
+    $page['something'] = [
+      '#markup' => 'test',
+    ];
+  }
+}