modelTypes: Move .subject_links from Message to StreamMessage.

The last field we need to do this for! :)

src/__tests__/lib/exampleData.js

@@ -296,7 +296,6 @@ const messagePropertiesBase = deepFreeze({
   is_me_message: false,
   // last_edit_timestamp omitted
   reactions: [],
-  subject_links: [],
   submessages: [],
 });
 
@@ -393,6 +392,7 @@ export const streamMessage = (args?: {|
     content_type: 'text/markdown',
     id: randMessageId(),
     subject: 'example topic',
+    subject_links: [],
     timestamp: 1556579727,
     type: 'stream',
   };

src/api/modelTypes.js

@@ -508,18 +508,11 @@ type MessageBase = $ReadOnly<{|
 
   /** Deprecated; a server implementation detail not useful in a client. */
   // recipient_id: number,
-
-  //
-  // Properties that behave differently for stream vs. private messages.
-  // TODO: Move all these to `PmMessage` and `StreamMessage`.
-
-  subject_links: $ReadOnlyArray<string>,
 |}>;
 
 export type PmMessage = $ReadOnly<{|
   ...MessageBase,
 
-  // TODO: Put PM-message fields here.
   type: 'private',
 
   // Notes from studying the server code:
@@ -556,7 +549,6 @@ export type PmMessage = $ReadOnly<{|
 export type StreamMessage = $ReadOnly<{|
   ...MessageBase,
 
-  // TODO: Put stream-message fields here.
   type: 'stream',
 
   /**
@@ -569,6 +561,7 @@ export type StreamMessage = $ReadOnly<{|
   stream_id: number,
 
   subject: string,
+  subject_links: $ReadOnlyArray<string>,
 |}>;
 
 /**

src/message/messagesReducer.js

@@ -140,7 +140,6 @@ export default (state: MessagesState = initialState, action: Action): MessagesSt
         const messageWithNewCommonFields: M = {
           ...(oldMessage: M),
           content: action.rendered_content || oldMessage.content,
-          subject_links: action.subject_links || oldMessage.subject_links,
           edit_history: [
             action.orig_rendered_content
               ? action.orig_subject !== undefined
@@ -170,7 +169,8 @@ export default (state: MessagesState = initialState, action: Action): MessagesSt
         return messageWithNewCommonFields.type === 'stream'
           ? {
               ...messageWithNewCommonFields,
-              subject: action.subject || oldMessage.subject,
+              subject: action.subject || messageWithNewCommonFields.subject,
+              subject_links: action.subject_links || messageWithNewCommonFields.subject_links,
             }
           : {
               ...messageWithNewCommonFields,