fix(remove user): handles user removal failures more gracefully

Author: mvilanova

src/dispatch/case/flows.py

@@ -197,20 +197,42 @@ def case_remove_participant_flow(
             log.warning("No conversation enabled for this case.")
             return
 
-        slack_conversation_plugin.instance.remove_user(
-            conversation_id=case.conversation.channel_id,
-            user_email=user_email
-        )
+        try:
+            slack_conversation_plugin.instance.remove_user(
+                conversation_id=case.conversation.channel_id,
+                user_email=user_email
+            )
 
-        event_service.log_case_event(
-                db_session=db_session,
-                source=slack_conversation_plugin.plugin.title,
-                description=f"{user_email} removed from conversation (channel ID: {case.conversation.channel_id})",
-                case_id=case.id,
-                type=EventType.participant_updated,
-        )
+            event_service.log_case_event(
+                    db_session=db_session,
+                    source=slack_conversation_plugin.plugin.title,
+                    description=f"{user_email} removed from conversation (channel ID: {case.conversation.channel_id})",
+                    case_id=case.id,
+                    type=EventType.participant_updated,
+            )
 
-        log.info(f"Removed {user_email} from conversation in channel {case.conversation.channel_id}")
+            log.info(f"Removed {user_email} from conversation in channel {case.conversation.channel_id}")
+
+        except Exception as slack_error:
+            # Check if this is a users_not_found error from Slack
+            error_msg = str(slack_error)
+            if "users_not_found" in error_msg:
+                log.warning(
+                    f"User {user_email} not found in Slack workspace. "
+                    f"They may have been deactivated or never had access. "
+                    f"Case conversation: {case.conversation.channel_id}"
+                )
+                # Still log the event to maintain audit trail
+                event_service.log_case_event(
+                    db_session=db_session,
+                    source=slack_conversation_plugin.plugin.title,
+                    description=f"Attempted to remove {user_email} from conversation but user not found in Slack",
+                    case_id=case.id,
+                    type=EventType.participant_updated,
+                )
+            else:
+                # Re-raise for other Slack errors
+                raise
 
     except Exception as e:
         log.exception(f"Failed to remove user from Slack conversation: {e}")

src/dispatch/incident/flows.py

@@ -1206,5 +1206,23 @@ def incident_remove_participant_flow(
 
         log.info(f"Removed {user_email} from conversation in channel {incident.conversation.channel_id}")
 
-    except Exception as e:
-        log.exception(f"Failed to remove user from Slack conversation: {e}")
+    except Exception as slack_error:
+        # Check if this is a users_not_found error from Slack
+        error_msg = str(slack_error)
+        if "users_not_found" in error_msg:
+            log.warning(
+                f"User {user_email} not found in Slack workspace. "
+                f"They may have been deactivated or never had access. "
+                f"Incident conversation: {incident.conversation.channel_id}"
+            )
+            # Still log the event to maintain audit trail
+            event_service.log_incident_event(
+                db_session=db_session,
+                source=slack_conversation_plugin.plugin.title,
+                description=f"Attempted to remove {user_email} from conversation but user not found in Slack",
+                incident_id=incident.id,
+                type=EventType.participant_updated,
+            )
+        else:
+            # Re-raise for other Slack errors
+            raise

src/dispatch/plugins/dispatch_slack/case/interactive.py

@@ -469,7 +469,23 @@ def engage(
         return
 
     engagement = form_data[DefaultBlockIds.description_input]
-    user = client.users_lookupByEmail(email=user_email)
+
+    try:
+        user = client.users_lookupByEmail(email=user_email)
+    except SlackApiError as e:
+        if e.response["error"] == SlackAPIErrorCode.USERS_NOT_FOUND:
+            log.warning(
+                f"Failed to find Slack user for email {user_email}. "
+                "User may have been deactivated or never had Slack access."
+            )
+            client.chat_postMessage(
+                text=f"Unable to engage user {user_email} - user not found in Slack workspace.",
+                channel=case.conversation.channel_id,
+                thread_ts=case.conversation.thread_id if case.has_thread else None,
+            )
+            return
+        else:
+            raise
 
     result = client.chat_postMessage(
         text="Engaging user...",
@@ -1983,9 +1999,19 @@ def edit_button_click(
     ack()
     case = case_service.get(db_session=db_session, case_id=int(context["subject"].id))
 
-    assignee_initial_user = client.users_lookupByEmail(email=case.assignee.individual.email)[
-        "user"
-    ]["id"]
+    try:
+        assignee_initial_user = client.users_lookupByEmail(email=case.assignee.individual.email)[
+            "user"
+        ]["id"]
+    except SlackApiError as e:
+        if e.response["error"] == SlackAPIErrorCode.USERS_NOT_FOUND:
+            log.warning(
+                f"Assignee {case.assignee.individual.email} not found in Slack workspace. "
+                "Using None for initial assignee selection."
+            )
+            assignee_initial_user = None
+        else:
+            raise
 
     blocks = [
         title_input(initial_value=case.title),

src/dispatch/plugins/dispatch_slack/plugin.py

@@ -390,13 +390,48 @@ def set_description(self, conversation_id: str, description: str):
         return set_conversation_description(client, conversation_id, description)
 
     def remove_user(self, conversation_id: str, user_email: str):
-        """Removes a user from a conversation."""
+        """Removes a user from a conversation.
+
+        Args:
+            conversation_id: The Slack conversation/channel ID
+            user_email: The email address of the user to remove
+
+        Returns:
+            The API response if successful, None if user not found
+
+        Raises:
+            SlackApiError: For non-recoverable Slack API errors
+        """
         client = create_slack_client(self.configuration)
-        user_id = resolve_user(client, user_email).get("id")
-        if user_id:
-            return remove_member_from_channel(
-                client=client, conversation_id=conversation_id, user_id=user_id
-            )
+
+        try:
+            user_info = resolve_user(client, user_email)
+            user_id = user_info.get("id")
+
+            if user_id:
+                return remove_member_from_channel(
+                    client=client, conversation_id=conversation_id, user_id=user_id
+                )
+            else:
+                logger.warning(
+                    "Cannot remove user %s from conversation %s: "
+                    "User ID not found in resolve_user response",
+                    user_email, conversation_id
+                )
+                return None
+
+        except SlackApiError as e:
+            if e.response.get("error") == SlackAPIErrorCode.USERS_NOT_FOUND:
+                logger.warning(
+                    "User %s not found in Slack workspace. "
+                    "Cannot remove from conversation %s. "
+                    "User may have been deactivated or never had Slack access.",
+                    user_email, conversation_id
+                )
+                return None
+            else:
+                # Re-raise for other Slack API errors
+                raise
 
     def add_bookmark(self, conversation_id: str, weblink: str, title: str):
         """Adds a bookmark to the conversation."""