fix: stop a film's save from erasing its custom field values

app/backend/next_views_ui.py

@@ -32127,8 +32127,14 @@ class shipped unstyled and fell back to the browser default button. */
       const container = document.getElementById("movieEditCustomFields");
       if (!container) return;
       const definitions = customFieldDefinitions().filter((field) => !field.archivedAt);
+      // `detail.movie.custom_values`, which is where `movie_detail_entity`
+      // attaches them. This read `detail.customValues`, a key only sync
+      // mutation results and the PUT response ever carry -- so every input
+      // rendered empty, `collectMovieEditCustomValues` turned each empty input
+      // into a null, and saving a film for any unrelated reason deleted every
+      // custom value it had. Silent on both sides.
       const values = new Map(
-        (detail?.customValues || []).map((item) => [String(item.key), item.value])
+        (detail?.movie?.custom_values || []).map((item) => [String(item.key), item.value])
       );
       container.classList.toggle("hidden", !definitions.length);
       container.innerHTML = definitions.map((field) => {

app/backend/tests/test_next_custom_fields_routes.py

@@ -191,6 +191,32 @@ def test_clearing_a_value_removes_the_row(self):
         self.assertEqual(response.status_code, 200, response.get_data(as_text=True))
         self.assertEqual(response.get_json()["customValues"], [])
 
+    def test_a_stored_value_comes_back_on_the_detail_payload_the_edit_form_reads(self):
+        """The round trip, not just the write.
+
+        The write always worked. What did not was reading it back: the edit form
+        looked for `detail.customValues`, and the detail payload attaches
+        `detail.movie.custom_values`. Every input rendered empty, an empty input
+        is sent as a null, and a null deletes the row -- so saving a film for
+        any unrelated reason erased its custom values.
+
+        Asserting the payload key here and the accessor in
+        `test_next_custom_fields_ui.py` is deliberate: a rename on either side
+        alone would restore exactly the same silence.
+        """
+        field = self._field()
+        movie_id = self._movie()
+        self.client.put(
+            f"/api/next/movies/{movie_id}/custom-values",
+            json={"values": {field["key"]: "Shelf B"}},
+        )
+        response = self.client.get(f"/api/next/movies/{movie_id}")
+        self.assertEqual(response.status_code, 200, response.get_data(as_text=True))
+        detail = response.get_json()["detail"]
+        self.assertNotIn("customValues", detail)
+        values = {row["key"]: row["value"] for row in detail["movie"]["custom_values"]}
+        self.assertEqual(values.get(field["key"]), "Shelf B")
+
     def test_a_value_on_a_missing_movie_is_a_404(self):
         field = self._field()
         response = self.client.put(

app/backend/tests/test_next_custom_fields_ui.py

@@ -143,6 +143,50 @@ def test_definitions_reach_the_spa_on_the_snapshot(self):
         self.assertIn("state?.customFields", block)
 
 
+class TheEditFormReadsTheKeyTheServerSendsTests(unittest.TestCase):
+    """The stored values have to arrive from the payload that carries them.
+
+    `renderMovieEditCustomFields` read `detail.customValues`. `movie_detail_entity`
+    attaches them as `detail.movie.custom_values`; `customValues` exists only on
+    sync-mutation results and on the PUT response, and nothing ever assigns it
+    on a detail payload. So every input rendered empty on every load.
+
+    That is not merely a display fault. `collectMovieEditCustomValues` turns an
+    empty input into `null`, `replace_movie_custom_values` deletes the row for a
+    `null`, and `saveMovieCustomValues` sends the whole collected map on every
+    save -- so opening a film, changing its title and pressing save silently
+    erased every custom value on that film. Nothing errored and nothing logged;
+    the values were simply gone the next time anyone looked.
+
+    Both halves are asserted, because a rename on either side reintroduces the
+    same silence: the accessor here, and the key the server actually attaches.
+    """
+
+    @classmethod
+    def setUpClass(cls):
+        cls.source = _source()
+
+    def test_the_renderer_reads_the_detail_payloads_own_key(self):
+        start = self.source.index("function renderMovieEditCustomFields")
+        block = self.source[start : start + 3200]
+        self.assertIn("detail?.movie?.custom_values", block)
+
+    def test_the_renderer_does_not_read_a_key_no_detail_payload_carries(self):
+        start = self.source.index("function renderMovieEditCustomFields")
+        block = self.source[start : start + 3200]
+        self.assertNotIn("detail?.customValues", block)
+
+    def test_the_server_attaches_the_values_the_renderer_reads(self):
+        with open(os.path.join(BACKEND_DIR, "next_app.py"), encoding="utf-8") as handle:
+            source = handle.read()
+        start = source.index("def movie_detail_entity")
+        block = source[start : start + 900]
+        self.assertIn("attach_movie_custom_values(conn, [movie])", block)
+        start = source.index("def attach_movie_custom_values")
+        block = source[start : start + 2500]
+        self.assertIn('"custom_values"', block)
+
+
 class SnapshotPublishesDefinitionsTests(unittest.TestCase):
     def test_the_dashboard_snapshot_carries_them_in_both_shapes(self):
         with open(os.path.join(BACKEND_DIR, "next_app.py"), encoding="utf-8") as handle: