From 0df2d753c4556fc25294fa9e1e1787a6765411db Mon Sep 17 00:00:00 2001
From: Manuel Raynaud <manu@raynaud.io>
Date: Mon, 1 Jun 2026 16:15:23 +0200
Subject: [PATCH] =?UTF-8?q?=F0=9F=93=88(backend)=20capture=20an=20event=20?=
 =?UTF-8?q?when=20a=20comment=20is=20created?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When a new comment is created, we capture an event related to this comment
creation.
---
 src/backend/core/api/viewsets.py              |  9 ++++-
 .../documents/test_api_documents_comments.py  | 36 ++++++++++++++-----
 src/backend/core/utils/analytics.py           |  3 ++
 3 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/src/backend/core/api/viewsets.py b/src/backend/core/api/viewsets.py
index 30d7b7551..e6eab55ef 100644
--- a/src/backend/core/api/viewsets.py
+++ b/src/backend/core/api/viewsets.py
@@ -3206,7 +3206,14 @@ class CommentViewSet(
     def perform_create(self, serializer):
         """Attach the request user as the comment author."""
         user = self.request.user if self.request.user.is_authenticated else None
-        serializer.save(user=user)
+        comment = serializer.save(user=user)
+
+        posthog_capture(
+            PosthogEventName.COMMENT_CREATED,
+            user,
+            {"comment_id": str(comment.id), "thread_id": str(comment.thread_id)},
+            document=self.get_document_or_404(),
+        )
 
     @drf.decorators.action(
         detail=True,
diff --git a/src/backend/core/tests/documents/test_api_documents_comments.py b/src/backend/core/tests/documents/test_api_documents_comments.py
index 6ae2c72f8..ec681f1ed 100644
--- a/src/backend/core/tests/documents/test_api_documents_comments.py
+++ b/src/backend/core/tests/documents/test_api_documents_comments.py
@@ -1,6 +1,7 @@
 """Test API for comments on documents."""
 
 import random
+from unittest import mock
 
 from django.contrib.auth.models import AnonymousUser
 
@@ -8,6 +9,7 @@ import pytest
 from rest_framework.test import APIClient
 
 from core import factories, models
+from core.utils.analytics import PosthogEventName
 
 pytestmark = pytest.mark.django_db
 
@@ -184,12 +186,21 @@ def test_create_comment_anonymous_user_public_document():
     )
     thread = factories.ThreadFactory(document=document)
     client = APIClient()
-    response = client.post(
-        f"/api/v1.0/documents/{document.id!s}/threads/{thread.id!s}/comments/",
-        {"body": "test"},
-    )
+    with mock.patch("core.api.viewsets.posthog_capture") as mock_capture:
+        response = client.post(
+            f"/api/v1.0/documents/{document.id!s}/threads/{thread.id!s}/comments/",
+            {"body": "test"},
+        )
     assert response.status_code == 201
 
+    # The comment creation should be tracked in PostHog
+    mock_capture.assert_called_once_with(
+        PosthogEventName.COMMENT_CREATED,
+        None,
+        {"comment_id": response.json()["id"], "thread_id": str(thread.id)},
+        document=document,
+    )
+
     assert response.json() == {
         "id": str(response.json()["id"]),
         "body": "test",
@@ -231,12 +242,21 @@ def test_create_comment_authenticated_user_accessible_document():
     thread = factories.ThreadFactory(document=document)
     client = APIClient()
     client.force_login(user)
-    response = client.post(
-        f"/api/v1.0/documents/{document.id!s}/threads/{thread.id!s}/comments/",
-        {"body": "test"},
-    )
+    with mock.patch("core.api.viewsets.posthog_capture") as mock_capture:
+        response = client.post(
+            f"/api/v1.0/documents/{document.id!s}/threads/{thread.id!s}/comments/",
+            {"body": "test"},
+        )
     assert response.status_code == 201
 
+    # The comment creation should be tracked in PostHog
+    mock_capture.assert_called_once_with(
+        PosthogEventName.COMMENT_CREATED,
+        user,
+        {"comment_id": response.json()["id"], "thread_id": str(thread.id)},
+        document=document,
+    )
+
     assert response.json() == {
         "id": str(response.json()["id"]),
         "body": "test",
diff --git a/src/backend/core/utils/analytics.py b/src/backend/core/utils/analytics.py
index a867d8dd1..335ac267b 100644
--- a/src/backend/core/utils/analytics.py
+++ b/src/backend/core/utils/analytics.py
@@ -29,6 +29,9 @@ class PosthogEventName(StrEnum):
     # Thread
     THREAD_CREATED = "thread_created"
 
+    # Comment
+    COMMENT_CREATED = "comment_created"
+
     # User
     USER_LOGIN = "user_login"