Provide a default Entity source class

Looks like a nice start. I guess there will be more changes required to actually support different entity types (e.g. the whole spool handling) but we can start with this and then partially convert the other things too.

+++ b/includes/simplenews.source.incundefined
@@ -434,13 +401,6 @@ class SimplenewsSourceNode implements SimplenewsSourceNodeInterface {
   /**
-   * Returns the corresponding newsletter.
-   */
-  public function getNewsletter() {
-    return $this->newsletter;
-  }
-
-  /**
    * Set the active subscriber.
    */
   public function setSubscriber($subscriber) {
@@ -455,6 +415,13 @@ class SimplenewsSourceNode implements SimplenewsSourceNodeInterface {

@@ -455,6 +415,13 @@ class SimplenewsSourceNode implements SimplenewsSourceNodeInterface {
   }
 
   /**
+   * Get Newsletter
+   */
+  public function getNewsletter() {
+    return $this->newsletter;
+  }

Why is this moved?

docblock should at least be kept?

+++ b/includes/simplenews.source.incundefined
@@ -653,10 +627,12 @@ class SimplenewsSourceNode implements SimplenewsSourceNodeInterface {
     // Build message body
     // Supported view modes: 'email_plain', 'email_html', 'email_textalt'
-    $build = node_view($this->node, 'email_' . $format);
+    $build = entity_view($this->getEntityType(), array($this->getEntity()), 'email_' . $format);
+    $build = reset($build[$this->getEntityType()]);

Hm. We only add those view modes to node. Note sure, we should probably at least document that they need to be created (e.g. with DS or a similar module) if another entity type should be used.

+++ b/includes/simplenews.source.incundefined
@@ -653,10 +627,12 @@ class SimplenewsSourceNode implements SimplenewsSourceNodeInterface {
+    list(,,$bundle) = entity_extract_ids($this->getEntityType(), $this->getEntity());
+    foreach (field_info_instances($this->getEntityType(),$bundle) as $field_name => $field) {

@@ -803,7 +779,8 @@ class SimplenewsSourceNode implements SimplenewsSourceNodeInterface {
-    foreach (field_info_instances('node', $this->node->type) as $field_name => $field_instance) {
+    list(,,$bundle) = entity_extract_ids($this->getEntityType(), $this->getEntity());

Missing spaces after some , (also for list())

+++ b/includes/simplenews.source.incundefined
@@ -856,7 +905,7 @@ abstract class SimplenewsSourceCacheStatic implements SimplenewsSourceCacheInter
-  public function __construct(SimplenewsSourceNodeInterface $source) {
+  public function __construct(SimplenewsSourceInterface $source) {

As mentioned in the other issue, this actually needs to be updated as well, it currently does rely on something node (with this patch entity) specific.

So we need need to specify Entity here or change they way the cid is generated in there.

Ok, committed and pushed.

The other issue can be closed as a duplicate now I think.