types: Add EditHistoryEvent and APIEditHistoryEvent types.

These types will help make iteration on this code easier.

Note that `user_id` can be null due to the fact that
edit history entries before March 2017 did not log
the user that made the edit, which was years after
supporting topic edits (discovered in test deployment
of migration on chat.zulip.org).

Co-authored-by: Lauryn Menard <lauryn.menard@gmail.com>

tools/linter_lib/custom_check.py

@@ -13,6 +13,7 @@ from zulint.custom_rules import Rule, RuleList
 FILES_WITH_LEGACY_SUBJECT = {
     # This basically requires a big DB migration:
     "zerver/lib/topic.py",
+    "zerver/lib/types.py",
     # This is for backward compatibility.
     "zerver/tests/test_legacy_subject.py",
     # Other migration-related changes require extreme care.
@@ -229,7 +230,7 @@ python_rules = RuleList(
     rules=[
         {
             "pattern": "subject|SUBJECT",
-            "exclude_pattern": "subject to the|email|outbox",
+            "exclude_pattern": "subject to the|email|outbox|edit_history_event",
             "description": "avoid subject as a var",
             "good_lines": ["topic_name"],
             "bad_lines": ['subject="foo"', " MAX_SUBJECT_LEN"],

zerver/lib/actions.py

@@ -161,7 +161,6 @@ from zerver.lib.string_validation import check_stream_name, check_stream_topic
 from zerver.lib.timestamp import datetime_to_timestamp, timestamp_to_datetime
 from zerver.lib.timezone import canonicalize_timezone
 from zerver.lib.topic import (
-    LEGACY_PREV_TOPIC,
     ORIG_TOPIC,
     RESOLVED_TOPIC_PREFIX,
     TOPIC_LINKS,
@@ -174,7 +173,12 @@ from zerver.lib.topic import (
     update_messages_for_topic_edit,
 )
 from zerver.lib.topic_mutes import add_topic_mute, get_topic_mutes, remove_topic_mute
-from zerver.lib.types import ProfileDataElementValue, ProfileFieldData, UnspecifiedValue
+from zerver.lib.types import (
+    EditHistoryEvent,
+    ProfileDataElementValue,
+    ProfileFieldData,
+    UnspecifiedValue,
+)
 from zerver.lib.upload import (
     claim_attachment,
     delete_avatar_image,
@@ -6695,7 +6699,7 @@ def do_update_message(
         "rendering_only": False,
     }
 
-    edit_history_event: Dict[str, Any] = {
+    edit_history_event: EditHistoryEvent = {
         "user_id": user_profile.id,
         "timestamp": event["edit_timestamp"],
     }
@@ -6869,7 +6873,7 @@ def do_update_message(
         event[ORIG_TOPIC] = orig_topic_name
         event[TOPIC_NAME] = topic_name
         event[TOPIC_LINKS] = topic_links(target_message.sender.realm_id, topic_name)
-        edit_history_event[LEGACY_PREV_TOPIC] = orig_topic_name
+        edit_history_event["prev_subject"] = orig_topic_name
 
     update_edit_history(target_message, timestamp, edit_history_event)
 
@@ -6879,16 +6883,14 @@ def do_update_message(
         assert stream_being_edited is not None
 
         # Other messages should only get topic/stream fields in their edit history.
-        topic_only_edit_history_event = {
-            k: v
-            for (k, v) in edit_history_event.items()
-            if k
-            not in [
-                "prev_content",
-                "prev_rendered_content",
-                "prev_rendered_content_version",
-            ]
+        topic_only_edit_history_event: EditHistoryEvent = {
+            "user_id": edit_history_event["user_id"],
+            "timestamp": edit_history_event["timestamp"],
         }
+        if topic_name is not None:
+            topic_only_edit_history_event["prev_subject"] = edit_history_event["prev_subject"]
+        if new_stream is not None:
+            topic_only_edit_history_event["prev_stream"] = edit_history_event["prev_stream"]
 
         messages_list = update_messages_for_topic_edit(
             acting_user=user_profile,

zerver/lib/message.py

@@ -38,7 +38,7 @@ from zerver.lib.streams import get_web_public_streams_queryset
 from zerver.lib.timestamp import datetime_to_timestamp
 from zerver.lib.topic import DB_TOPIC_NAME, MESSAGE__TOPIC, TOPIC_LINKS, TOPIC_NAME
 from zerver.lib.topic_mutes import build_topic_mute_checker, topic_is_muted
-from zerver.lib.types import DisplayRecipientT, UserDisplayRecipient
+from zerver.lib.types import DisplayRecipientT, EditHistoryEvent, UserDisplayRecipient
 from zerver.models import (
     MAX_TOPIC_NAME_LENGTH,
     Message,
@@ -502,7 +502,8 @@ class MessageDict:
         if last_edit_time is not None:
             obj["last_edit_timestamp"] = datetime_to_timestamp(last_edit_time)
             assert edit_history_json is not None
-            edit_history = orjson.loads(edit_history_json)
+            # Here we assume EditHistoryEvent == APIEditHistoryEvent
+            edit_history: List[EditHistoryEvent] = orjson.loads(edit_history_json)
             obj["edit_history"] = edit_history
 
         if Message.need_to_render_content(

zerver/lib/topic.py

@@ -8,6 +8,7 @@ from sqlalchemy.sql import ColumnElement, column, func, literal
 from sqlalchemy.types import Boolean, Text
 
 from zerver.lib.request import REQ
+from zerver.lib.types import EditHistoryEvent
 from zerver.models import Message, Stream, UserMessage, UserProfile
 
 # Only use these constants for events.
@@ -135,11 +136,11 @@ def user_message_exists_for_topic(
 
 
 def update_edit_history(
-    message: Message, last_edit_time: datetime, edit_history_event: Dict[str, Any]
+    message: Message, last_edit_time: datetime, edit_history_event: EditHistoryEvent
 ) -> None:
     message.last_edit_time = last_edit_time
     if message.edit_history is not None:
-        edit_history = orjson.loads(message.edit_history)
+        edit_history: List[EditHistoryEvent] = orjson.loads(message.edit_history)
         edit_history.insert(0, edit_history_event)
     else:
         edit_history = [edit_history_event]
@@ -154,7 +155,7 @@ def update_messages_for_topic_edit(
     topic_name: Optional[str],
     new_stream: Optional[Stream],
     old_stream: Stream,
-    edit_history_event: Dict[str, Any],
+    edit_history_event: EditHistoryEvent,
     last_edit_time: datetime,
 ) -> List[Message]:
     propagate_query = Q(recipient_id=old_stream.recipient_id, subject__iexact=orig_topic_name)

zerver/lib/types.py

@@ -89,3 +89,40 @@ class UnspecifiedValue:
     """
 
     pass
+
+
+class APIEditHistoryEvent(TypedDict, total=False):
+    """Format of legacy edit history events in the API. Contains legacy
+    fields like LEGACY_PREV_TOPIC that we intend to remove from the
+    API eventually.
+    """
+
+    # Commented fields are fields we plan to add.
+    user_id: Optional[int]
+    timestamp: int
+    prev_stream: int
+    # stream: int
+    prev_subject: str
+    # prev_topic: str
+    # topic: str
+    prev_content: str
+    prev_rendered_content: Optional[str]
+    prev_rendered_content_version: Optional[int]
+
+
+class EditHistoryEvent(TypedDict, total=False):
+    """
+    Database format for edit history events.
+    """
+
+    # Commented fields are fields we plan to add.
+    user_id: Optional[int]
+    timestamp: int
+    prev_stream: int
+    # stream: int
+    prev_subject: str
+    # prev_topic: str
+    # topic: str
+    prev_content: str
+    prev_rendered_content: Optional[str]
+    prev_rendered_content_version: Optional[int]