drafts: Use "topic" internally.

We still have to support "subject" for old drafts,
but we write "topic" for new drafts.

frontend_tests/node_tests/drafts.js

@@ -59,9 +59,23 @@ function stub_timestamp(timestamp, func) {
     Date.prototype.getTime = original_func;
 }
 
+var legacy_draft = {
+    stream: "stream",
+    subject: "lunch",
+    type: "stream",
+    content: "whatever",
+};
+
+var compose_args_for_legacy_draft = {
+    stream: "stream",
+    subject: "lunch",
+    type: "stream",
+    content: "whatever",
+};
+
 var draft_1 = {
     stream: "stream",
-    subject: "topic",
+    topic: "topic",
     type: "stream",
     content: "Test Stream Message",
 };
@@ -78,6 +92,13 @@ var short_msg = {
     content: "a",
 };
 
+run_test('legacy', () => {
+    assert.deepEqual(
+        drafts.restore_message(legacy_draft),
+        compose_args_for_legacy_draft
+    );
+});
+
 run_test('draft_model', () => {
     var draft_model = drafts.draft_model;
     var ls = localstorage();
@@ -148,7 +169,7 @@ run_test('snapshot_message', () => {
             return draft.stream;
         };
         global.compose_state.topic = function () {
-            return draft.subject;
+            return draft.topic;
         };
     }
 

static/js/drafts.js

@@ -81,7 +81,7 @@ exports.snapshot_message = function () {
         message.private_message_recipient = recipient;
     } else {
         message.stream = compose_state.stream_name();
-        message.subject = compose_state.topic();
+        message.topic = compose_state.topic();
     }
     return message;
 };
@@ -97,7 +97,7 @@ exports.restore_message = function (draft) {
         compose_args = {
             type: 'stream',
             stream: draft.stream,
-            subject: draft.subject,
+            subject: util.get_draft_topic(draft),
             content: draft.content,
         };
 
@@ -246,8 +246,11 @@ exports.setup_page = function (callback) {
                 // single space char for proper rendering of the stream label
                 var space_string = new Handlebars.SafeString(" ");
                 var stream = draft.stream.length > 0 ? draft.stream : space_string;
-                var draft_topic = draft.subject.length === 0 ?
-                    compose.empty_topic_placeholder() : draft.subject;
+                var draft_topic = util.get_draft_topic(draft);
+
+                if (draft_topic === '') {
+                    draft_topic = compose.empty_topic_placeholder();
+                }
 
                 formatted = {
                     draft_id: id,

static/js/util.js

@@ -291,6 +291,11 @@ exports.get_match_topic = function (obj) {
     return obj.match_subject;
 };
 
+exports.get_draft_topic = function (obj) {
+    // We will need to support subject for old drafts.
+    return obj.topic || obj.subject || '';
+};
+
 exports.set_topic = function (obj, topic) {
     obj.subject = topic;
 };