message_helper: Be more explicit about converting subject to topic.

tools/linter_lib/custom_check.py

@@ -124,6 +124,7 @@ js_rules = RuleList(
                 "web/src/message_store.ts",
                 "web/src/types.ts",
                 "web/src/util.ts",
+                "web/src/message_helper.ts",
                 "web/tests/",
             },
             "exclude_pattern": "emails",

web/src/message_helper.js

@@ -38,7 +38,10 @@ export function process_new_message(message) {
 
     switch (message.type) {
         case "stream":
-            util.convert_message_topic(message);
+            if (message.topic === undefined) {
+                message.topic = message.subject;
+            }
+            delete message.subject;
             message.is_stream = true;
             message.reply_to = message.sender_email;
 

web/src/util.ts

@@ -269,12 +269,6 @@ export function is_topic_synonym(operator: string): boolean {
     return operator === "subject";
 }
 
-export function convert_message_topic(message: Message): void {
-    if (message.type === "stream" && message.topic === undefined) {
-        message.topic = message.subject;
-    }
-}
-
 // TODO: When "stream" is renamed to "channel", update these stream
 // synonym helper functions for the reverse logic.
 export function is_stream_synonym(text: string): boolean {

web/tests/example2.test.js

@@ -42,7 +42,7 @@ const messages = {
         stream_id: denmark_stream.stream_id,
         type: "stream",
         flags: ["has_alert_word"],
-        topic: "copenhagen",
+        subject: "copenhagen",
         // note we don't have every field that a "real" message
         // would have, and that can be fine
     },
@@ -91,7 +91,7 @@ run_test("unread", () => {
     assert.equal(unread.num_unread_for_topic(stream_id, topic_name), 0);
 
     let in_message = {...messages.isaac_to_denmark_stream};
-    in_message = message_store.set_message_booleans(in_message);
+    in_message = message_helper.process_new_message(in_message);
 
     unread.process_loaded_messages([in_message]);
     assert.equal(unread.num_unread_for_topic(stream_id, topic_name), 1);