refactor: Extract people.maybe_incr_recipient_count().

This logic used to be in extract_people_from_message(), but
we are deprecating extract_people_from_message(), whereas
the maybe_incr_recipient_count() function has logic that we
want to keep.

frontend_tests/node_tests/people.js

@@ -443,15 +443,58 @@ initialize();
         sender_id: maria.user_id,
         sender_email: maria.email,
     };
+    assert(!people.is_known_user_id(maria.user_id));
     people.extract_people_from_message(message);
     assert(people.is_known_user_id(maria.user_id));
+}());
 
-    message = {
+initialize();
+
+(function test_maybe_incr_recipient_count() {
+    var maria = {
+        email: 'athens@example.com',
+        user_id: 452,
+        full_name: 'Maria Athens',
+    };
+    people.add_in_realm(maria);
+
+    var unknown_user = {
+        email: 'unknown@example.com',
+        user_id: 500,
+        unknown_local_echo_user: true,
+    };
+
+    var message = {
         type: 'private',
         display_recipient: [maria],
         sent_by_me: true,
     };
-    people.extract_people_from_message(message);
+    assert.equal(people.get_recipient_count(maria), 0);
+    people.maybe_incr_recipient_count(message);
+    assert.equal(people.get_recipient_count(maria), 1);
+
+    // Test all the no-op conditions to get test
+    // coverage.
+    message = {
+        type: 'private',
+        sent_by_me: false,
+        display_recipient: [maria],
+    };
+    people.maybe_incr_recipient_count(message);
+    assert.equal(people.get_recipient_count(maria), 1);
+
+    message = {
+        type: 'private',
+        sent_by_me: true,
+        display_recipient: [unknown_user],
+    };
+    people.maybe_incr_recipient_count(message);
+    assert.equal(people.get_recipient_count(maria), 1);
+
+    message = {
+        type: 'stream',
+    };
+    people.maybe_incr_recipient_count(message);
     assert.equal(people.get_recipient_count(maria), 1);
 }());
 

static/js/message_store.js

@@ -123,6 +123,7 @@ exports.add_message_metadata = function (message) {
     exports.set_message_booleans(message, message.flags);
 
     people.extract_people_from_message(message);
+    people.maybe_incr_recipient_count(message);
 
     var sender = people.get_person_from_user_id(message.sender_id);
     if (sender) {

static/js/people.js

@@ -757,12 +757,28 @@ exports.extract_people_from_message = function (message) {
                     is_bot: person.is_bot || false,
                 });
             }
+        }
+    });
+};
+
+exports.maybe_incr_recipient_count = function (message) {
+    if (message.type !== 'private') {
+        return;
+    }
+
+    if (!message.sent_by_me) {
+        return;
+    }
 
-            if (message.type === 'private' && message.sent_by_me) {
     // Track the number of PMs we've sent to this person to improve autocomplete
+    _.each(message.display_recipient, function (person) {
+
+        if (person.unknown_local_echo_user) {
+            return;
+        }
+
+        var user_id = person.user_id || person.id;
         exports.incr_recipient_count(user_id);
-            }
-        }
     });
 };