Print warning when comment_sort is set after fetch

(cherry picked from commit 4999b4e13c9423a9625a29dbca183a826b2e6935)

CHANGES.rst

@@ -11,6 +11,15 @@ Unreleased
 
 **Added**
 
+- Log a warning if a submission's ``comment_sort`` attribute is updated after the
+  submission has already been fetched and a ``warn_comment_sort`` config setting to turn
+  off the warning.
+
+7.4.0 (2021/07/30)
+------------------
+
+**Added**
+
 - :meth:`~.WikiPage.discussions` to obtain site-wide link submissions that link to the
   WikiPage.
 - :meth:`.revert` to revert a WikiPage to a specified revision.

asyncpraw/config.py

@@ -114,6 +114,9 @@ def _initialize_attributes(self):
         self.check_for_updates = self._config_boolean(
             self._fetch_or_not_set("check_for_updates")
         )
+        self.warn_comment_sort = self._config_boolean(
+            self._fetch_default("warn_comment_sort", True)
+        )
         self.kinds = {
             x: self._fetch(f"{x}_kind")
             for x in [

asyncpraw/models/reddit/submission.py

@@ -1,6 +1,7 @@
 """Provide the Submission class."""
 from typing import TYPE_CHECKING, Any, Dict, List, Optional, Union
 from urllib.parse import urljoin
+from warnings import warn
 
 from asyncprawcore import Conflict
 
@@ -619,6 +620,17 @@ def __setattr__(self, attribute: str, value: Any):
             value = Subreddit(self._reddit, value)
         elif attribute == "poll_data":
             value = PollData(self._reddit, value)
+        elif (
+            attribute == "comment_sort"
+            and hasattr(self, "_fetched")
+            and self._fetched
+            and hasattr(self, "_reddit")
+            and self._reddit.config.warn_comment_sort
+        ):
+            warn(
+                "The comments for this submission have already been fetched, "
+                "so the updated comment_sort will not have any effect"
+            )
         super().__setattr__(attribute, value)
 
     def _chunk(self, other_submissions, chunk_size):

docs/getting_started/configuration/options.rst

@@ -92,6 +92,8 @@ PRAW.
 :timeout: Controls the amount of time Async PRAW will wait for a request from Reddit to
     complete before throwing an exception. By default, Async PRAW waits 16 seconds
     before throwing an exception.
+:warn_comment_sort: When ``true``, log a warning when the ``comment_sort`` attribute of
+    a submission is updated after _fetch() has been called. (default: ``true``)
 
 .. _custom_options:
 

tests/unit/models/reddit/test_submission.py

@@ -47,6 +47,27 @@ def test_construct_failure(self):
         with pytest.raises(ValueError):
             Submission(self.reddit, url="")
 
+    @pytest.mark.filterwarnings("error", category=UserWarning)
+    async def test_comment_sort_warning(self):
+        with pytest.raises(UserWarning) as excinfo:
+            submission = await self.reddit.submission("1234", lazy=True)
+            submission._fetched = True
+            submission.comment_sort = "new"
+        assert (
+            excinfo.value.args[0]
+            == "The comments for this submission have already been fetched, "
+            "so the updated comment_sort will not have any effect"
+        )
+
+    @pytest.mark.filterwarnings("error", category=UserWarning)
+    @pytest.LogCaptureFixture
+    async def test_comment_sort_warning__disabled(self, caplog):
+        self.reddit.config.warn_comment_sort = False
+        submission = await self.reddit.submission("1234", lazy=False)
+        submission._fetched = True
+        submission.comment_sort = "new"
+        assert caplog.records == []
+
     def test_construct_from_url(self):
         assert Submission(self.reddit, url="http://my.it/2gmzqe") == "2gmzqe"