message_fetch: Deduplicate logic for finish_older_batch.

Previously, each individual caller of load_messages that passed
num_before > 0 would do its own manual management of fetch_status;
now, we just do it inside load_messages.

frontend_tests/node_tests/fetch_status.js

@@ -48,11 +48,13 @@ run_test('basics', () => {
     can_load_history();
     has_not_found_newest();
 
-    fetch_status.finish_initial_narrow({
+    var data = {
         found_oldest: true,
         found_newest: true,
         history_limited: true,
-    });
+    };
+    fetch_status.finish_initial_narrow(data);
+    fetch_status.finish_older_batch(data);
 
     has_found_newest();
     blocked_newer();
@@ -67,11 +69,13 @@ run_test('basics', () => {
     blocked_older();
     can_load_history();
 
-    fetch_status.finish_initial_narrow({
+    data = {
         found_oldest: false,
         found_newest: false,
         history_limited: false,
-    });
+    };
+    fetch_status.finish_initial_narrow(data);
+    fetch_status.finish_older_batch(data);
 
     can_load_older();
     can_load_newer();

static/js/fetch_status.js

@@ -15,10 +15,7 @@ var FetchStatus = function () {
 
     self.finish_initial_narrow = function (opts) {
         loading_newer = false;
-        loading_older = false;
-        found_oldest = opts.found_oldest;
         found_newest = opts.found_newest;
-        history_limited = opts.history_limited;
     };
 
     self.start_older_batch = function () {

static/js/message_fetch.js

@@ -56,11 +56,24 @@ function process_result(data, opts) {
     stream_list.maybe_scroll_narrow_into_view();
 
     if (opts.cont !== undefined) {
-        opts.cont(data, opts);
+        opts.cont(data);
     }
 }
 
 function get_messages_success(data, opts) {
+    if (opts.num_before > 0) {
+        opts.msg_list.fetch_status.finish_older_batch({
+            found_oldest: data.found_oldest,
+            history_limited: data.history_limited,
+        });
+        if (opts.msg_list === home_msg_list) {
+            message_list.all.fetch_status.finish_older_batch({
+                found_oldest: data.found_oldest,
+                history_limited: data.history_limited,
+            });
+        }
+    }
+
     if (opts.msg_list.narrowed && opts.msg_list !== current_msg_list) {
         // We unnarrowed before receiving new messages so
         // don't bother processing the newly arrived messages.
@@ -223,17 +236,7 @@ exports.do_backfill = function (opts) {
         num_before: opts.num_before,
         num_after: 0,
         msg_list: msg_list,
-        cont: function (data) {
+        cont: function () {
-            msg_list.fetch_status.finish_older_batch({
-                found_oldest: data.found_oldest,
-                history_limited: data.history_limited,
-            });
-            if (msg_list === home_msg_list) {
-                message_list.all.fetch_status.finish_older_batch({
-                    found_oldest: data.found_oldest,
-                    history_limited: data.history_limited,
-                });
-            }
             if (opts.cont) {
                 opts.cont();
             }
@@ -291,7 +294,7 @@ exports.start_backfilling_messages = function () {
 
 exports.initialize = function () {
     // get the initial message list
-    function load_more(data, opts) {
+    function load_more(data) {
         // If we received the initially selected message, select it on the client side,
         // but not if the user has already selected another one during load.
         //
@@ -303,19 +306,6 @@ exports.initialize = function () {
                                      target_scroll_offset: page_params.initial_offset});
         }
 
-        if (opts.num_before > 0) {
-            // Only the initial call with num_before=consts.num_before_pointer
-            // has an older batch to finish.
-            home_msg_list.fetch_status.finish_older_batch({
-                found_oldest: data.found_oldest,
-                history_limited: data.history_limited,
-            });
-            message_list.all.fetch_status.finish_older_batch({
-                found_oldest: data.found_oldest,
-                history_limited: data.history_limited,
-            });
-        }
-
         home_msg_list.fetch_status.finish_newer_batch({
             found_newest: data.found_newest,
         });