From 8376acb3b83588bc38092bca51c85b0000693f38 Mon Sep 17 00:00:00 2001
From: Tim Abbott <tabbott@zulip.com>
Date: Fri, 4 Mar 2022 11:53:13 -0800
Subject: [PATCH] edit_history: Add comments detailing when user_id can be
 null.

This is already in the API documentation, but I think it's worth
having here.
---
 zerver/lib/types.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/zerver/lib/types.py b/zerver/lib/types.py
index a765ab0adf..f1ef411ba4 100644
--- a/zerver/lib/types.py
+++ b/zerver/lib/types.py
@@ -96,6 +96,10 @@ class EditHistoryEvent(TypedDict, total=False):
     Database format for edit history events.
     """
 
+    # user_id is null for precisely those edit history events
+    # predating March 2017, when we started tracking the person who
+    # made edits, which is still years after the introduction of topic
+    # editing support in Zulip.
     user_id: Optional[int]
     timestamp: int
     prev_stream: int
@@ -112,6 +116,7 @@ class FormattedEditHistoryEvent(TypedDict, total=False):
     Extended format used in the edit history endpoint.
     """
 
+    # See EditHistoryEvent for details on when this can be null.
     user_id: Optional[int]
     timestamp: int
     prev_stream: int