msglist: Don't assume people with the same name are the same.

src/__tests__/lib/exampleData.js

@@ -375,6 +375,7 @@ const outboxMessageBase: $Diff<Outbox, {| id: mixed, timestamp: mixed |}> = deep
   reactions: [],
   sender_email: selfUser.email,
   sender_full_name: selfUser.full_name,
+  sender_id: selfUser.user_id,
   subject: 'test topic',
   // timestamp: ...,
   type: 'stream',

src/message/__tests__/renderMessages-test.js

@@ -33,6 +33,7 @@ describe('renderMessages', () => {
         timestamp: 123,
         type: 'stream',
         id: 1,
+        sender_email: 'john@example.com',
         sender_full_name: 'John Doe',
         display_recipient: 'general',
         subject: '',
@@ -42,6 +43,7 @@ describe('renderMessages', () => {
         timestamp: 124,
         type: 'stream',
         id: 2,
+        sender_email: 'john@example.com',
         sender_full_name: 'John Doe',
         display_recipient: 'general',
         subject: '',
@@ -51,6 +53,7 @@ describe('renderMessages', () => {
         timestamp: 125,
         type: 'stream',
         id: 3,
+        sender_email: 'john@example.com',
         sender_full_name: 'John Doe',
         display_recipient: 'general',
         subject: '',
@@ -72,6 +75,7 @@ describe('renderMessages', () => {
         timestamp: 123,
         type: 'stream',
         id: 1,
+        sender_email: 'john@example.com',
         sender_full_name: 'John',
         display_recipient: 'general',
         subject: '',
@@ -81,6 +85,7 @@ describe('renderMessages', () => {
         timestamp: 124,
         type: 'stream',
         id: 2,
+        sender_email: 'mark@example.com',
         sender_full_name: 'Mark',
         display_recipient: 'general',
         subject: '',
@@ -90,6 +95,7 @@ describe('renderMessages', () => {
         timestamp: 125,
         type: 'stream',
         id: 3,
+        sender_email: 'peter@example.com',
         sender_full_name: 'Peter',
         display_recipient: 'general',
         subject: '',
@@ -111,6 +117,7 @@ describe('renderMessages', () => {
         timestamp: 123,
         type: 'private',
         id: 1,
+        sender_email: 'john@example.com',
         sender_full_name: 'John',
         avatar_url: '',
         display_recipient: [{ email: 'john@example.com' }, { email: 'mark@example.com' }],
@@ -119,6 +126,7 @@ describe('renderMessages', () => {
         timestamp: 123,
         type: 'private',
         id: 2,
+        sender_email: 'mark@example.com',
         sender_full_name: 'Mark',
         avatar_url: '',
         display_recipient: [{ email: 'john@example.com' }, { email: 'mark@example.com' }],

src/message/renderMessages.js

@@ -31,11 +31,13 @@ export default (
         data: [],
       });
     }
+
+    // TODO(#3764): Use sender_id, not sender_email.  Needs making
+    //   Outbox#sender_id required; which needs a migration to drop Outbox
+    //   values that lack it; which is fine once the release that adds it
+    //   has been out for a few weeks.
     const shouldGroupWithPrev =
-      !diffRecipient
-      && !diffDays
-      && prevItem
-      && prevItem.sender_full_name === item.sender_full_name;
+      !diffRecipient && !diffDays && prevItem && prevItem.sender_email === item.sender_email;
 
     sections[sections.length - 1].data.push({
       key: item.id,

src/outbox/outboxActions.js

@@ -186,6 +186,7 @@ export const addToOutbox = (narrow: Narrow, content: string) => async (
       id: localTime,
       sender_full_name: ownUser.full_name,
       sender_email: ownUser.email,
+      sender_id: ownUser.user_id,
       avatar_url: ownUser.avatar_url,
       isOutbox: true,
       reactions: [],

src/types.js

@@ -175,14 +175,22 @@ export type Outbox = {|
   // It's used for sending the message to the server.
   markdownContent: string,
 
-  // These fields are modeled on `Message`.
+  // The remaining fields are modeled on `Message`.
+
   avatar_url: string | null,
   content: string,
   display_recipient: $FlowFixMe, // `string` for type stream, else PmRecipientUser[].
   id: number,
   reactions: Reaction[],
   sender_email: string,
   sender_full_name: string,
+
+  // TODO(#3764): Make sender_id required.  Needs a migration to drop Outbox
+  //   values that lack it; which is fine once the release that adds it has
+  //   been out for a few weeks.
+  //   (Also drop the hack line about it in MessageLike.)
+  sender_id?: number,
+
   subject: string,
   timestamp: number,
   type: 'stream' | 'private',
@@ -194,7 +202,7 @@ export type Outbox = {|
  * Flow reasonably dispermits certain classes of access on union types. In
  * particular,
  * ```
- * const { sender_id } = (message: Message | Outbox);  // error
+ * const { match_content } = (message: Message | Outbox);  // error
  * ```
  * is not allowed. However, as long as you're prepared to handle values of
  * `undefined`, it's both JavaScript-legal to do so and occasionally convenient.
@@ -203,7 +211,7 @@ export type Outbox = {|
  * subtype of `Message | Outbox`, but which Flow will permit us to directly (and
  * soundly) destructure certain `Message`-only fields from:
  * ```
- * const { sender_id } = (message: MessageLike);  // ok!
+ * const { match_content } = (message: MessageLike);  // ok!
  * ```
  *
  * * Note: `MessageLike` <: `Message | Outbox`, but the converse does not hold.
@@ -221,6 +229,7 @@ export type MessageLike =
   | $ReadOnly<{
       // $Shape<T> is unsound, per Flow docs, but $ReadOnly<$Shape<T>> is not
       ...$Shape<{ [$Keys<Message>]: void }>,
+      sender_id?: number, // TODO: Drop this once required in Outbox.
       ...Outbox,
     }>;