From aa7483516477c5f81d4e27a8d804b6bc6022954a Mon Sep 17 00:00:00 2001
From: Jake Dallimore <jake@moodle.com>
Date: Fri, 2 Nov 2018 10:10:37 +0800
Subject: [PATCH] MDL-63549 core_message: exclude conversations where all
 messages deleted

If there are no recent messages for an individual conversation for the
user, then we exclude that conversation from the results.
---
 message/classes/api.php    | 11 ++++++-----
 message/tests/api_test.php | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/message/classes/api.php b/message/classes/api.php
index 08243942a69..5e2c9b1d57f 100644
--- a/message/classes/api.php
+++ b/message/classes/api.php
@@ -543,11 +543,12 @@ class api {
         // Now, create the final return structure.
         $arrconversations = [];
         foreach ($conversations as $conversation) {
-            // It's possible other users have been deleted.
-            // In cases like this, we still want to include the conversation if it's of type 'group'.
-            // Individual conversations are skipped if the other member has been deleted.
-            if (isset($deletedmembers[$conversation->id]) &&
-                    $conversation->conversationtype == self::MESSAGE_CONVERSATION_TYPE_INDIVIDUAL) {
+            // Do not include any individual conversation which:
+            // a) Contains a deleted member or
+            // b) Does not contain a recent message for the user (this happens if the user has deleted all messages).
+            // Group conversations with deleted users or no messages are always returned.
+            if ($conversation->conversationtype == self::MESSAGE_CONVERSATION_TYPE_INDIVIDUAL
+                    && (isset($deletedmembers[$conversation->id]) || empty($conversation->messageid))) {
                 continue;
             }
 
diff --git a/message/tests/api_test.php b/message/tests/api_test.php
index d75284306ab..ade68433760 100644
--- a/message/tests/api_test.php
+++ b/message/tests/api_test.php
@@ -927,6 +927,40 @@ class core_message_api_testcase extends core_message_messagelib_testcase {
         $this->assertEquals($gc4->id, $conversations[3]->id);
     }
 
+    /**
+     * Test confirming the behaviour of get_conversations() when users delete all messages.
+     */
+    public function test_get_conversations_deleted_messages() {
+        // Get a bunch of conversations, some group, some individual and in different states.
+        list($user1, $user2, $user3, $user4, $ic1, $ic2, $ic3,
+            $gc1, $gc2, $gc3, $gc4, $gc5, $gc6) = $this->create_conversation_test_data();
+
+        $conversations = \core_message\api::get_conversations($user1->id);
+        $this->assertCount(6, $conversations);
+
+        // Delete all messages from a group conversation the user is in - it should be returned.
+        $this->assertTrue(\core_message\api::is_user_in_conversation($user1->id, $gc2->id));
+        $convmessages = \core_message\api::get_conversation_messages($user1->id, $gc2->id);
+        $messages = $convmessages['messages'];
+        foreach ($messages as $message) {
+            \core_message\api::delete_message($user1->id, $message->id);
+        }
+        $conversations = \core_message\api::get_conversations($user1->id);
+        $this->assertCount(6, $conversations);
+        $this->assertContains($gc2->id, array_column($conversations, 'id'));
+
+        // Delete all messages from an individual conversation the user is in - it should not be returned.
+        $this->assertTrue(\core_message\api::is_user_in_conversation($user1->id, $ic1->id));
+        $convmessages = \core_message\api::get_conversation_messages($user1->id, $ic1->id);
+        $messages = $convmessages['messages'];
+        foreach ($messages as $message) {
+            \core_message\api::delete_message($user1->id, $message->id);
+        }
+        $conversations = \core_message\api::get_conversations($user1->id);
+        $this->assertCount(5, $conversations);
+        $this->assertNotContains($ic1->id, array_column($conversations, 'id'));
+    }
+
     /**
      * Test verifying the behaviour of get_conversations() when fetching favourite conversations.
      */