Create a more generic superclass of \Drupal\Core\Render\BubbleableMetadata

Either CacheableMetadata or CacheabilityMetadata are the names that come to mind.

1. +++ b/core/lib/Drupal/Core/Cache/CacheableMetadata.php
   @@ -0,0 +1,105 @@
   + * Defines an interface for objects which may be used by other cached objects.
   + *
   + * This extended interface defines setters so that the object may have cache
   

   This is not an interface, but a class :)

2. +++ b/core/lib/Drupal/Core/Cache/CacheableMetadataInterface.php
   @@ -0,0 +1,73 @@
   +interface CacheableMetadataInterface extends CacheableDependencyInterface {
   

   Why is this interface necessary? Why would anyone ever want to swap out the CacheableMetadata class?

Blocks #2335661: Outbound path & route processors must specify cacheability metadata.

Patch looks great; now just a matter of moving a bunch of BubbleableMetadataTest to CacheableMetadataTest.

+++ b/core/lib/Drupal/Core/Cache/CacheableMetadata.php
@@ -7,14 +7,11 @@
+ * Defines a generic class for storing and fetching cacheability metadata.

s/storing and fetching/passing/

But that's a nit.

Failing tests :(

+++ b/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php
@@ -0,0 +1,72 @@
+  public function testAddCacheTags() {
+    $metadata = new CacheableMetadata();
+    $add_expected = [
+      [ [], [] ],
+      [ ['foo:bar'], ['foo:bar'] ],
+      [ ['foo:baz'], ['foo:bar', 'foo:baz'] ],
+      [ ['axx:first', 'foo:baz'], ['axx:first', 'foo:bar', 'foo:baz'] ],
+      [ [], ['axx:first', 'foo:bar', 'foo:baz'] ],
+      [ ['axx:first'], ['axx:first', 'foo:bar', 'foo:baz'] ],
+    ];
+
+    foreach ($add_expected as $data) {
+      list($add, $expected) = $data;
+      $metadata->addCacheTags($add);
+      $this->assertEquals($expected, $metadata->getCacheTags());
+    }
+  }

Could use a data provider.

Oh, sorry, missed that.

This issue addresses a major bug and is allowed per https://www.drupal.org/core/beta-changes. Committed a0ee087 and pushed to 8.0.x. Thanks!

diff --git a/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php b/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php
index a292e9d..7918d60 100644
--- a/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php
+++ b/core/tests/Drupal/Tests/Core/Cache/CacheableMetadataTest.php
@@ -44,7 +44,7 @@ public function testAddCacheTags() {
    * Test valid and invalid values as max age.
    *
    * @covers ::setCacheMaxAge
-   * @dataProvider providersetCacheMaxAge
+   * @dataProvider providerSetCacheMaxAge
    */
   public function testSetCacheMaxAge($data, $expect_exception) {
     $metadata = new CacheableMetadata();
@@ -58,7 +58,7 @@ public function testSetCacheMaxAge($data, $expect_exception) {
   /**
    * Data provider for testSetCacheMaxAge.
    */
-  public function providersetCacheMaxAge() {
+  public function providerSetCacheMaxAge() {
    return [
      [0 , FALSE],
      ['http', TRUE],

Fixed a capitalisation thing on commit.

+1 to this change!