fix(recipe): measurement_interval_minutes e image_path si possono di nuovo azzerare (#37.3)

recipe_editor.html saveRecipe(): i due campi vengono sempre inviati nel
payload (valore o null esplicito), non più omessi quando svuotati.
recipe_service.py _header_fields(): per i due campi (unica eccezione
concordata al confine dei lotti, righe ~37-60) distingue "non inviato" da
"inviato null" con model_fields_set, invece di getattr(...) is not None —
altrimenti un null esplicito veniva scartato allo stesso modo di un campo
assente e il valore restava bloccato per sempre. Gli altri campi header
(name, description, requires_*, allow_manual_input) non toccati.
Test backend in test_recipes.py: TestUpdateRecipeClearNullableFields.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/backend/services/recipe_service.py

@@ -34,13 +34,34 @@ HEADER_FIELDS = (
 )
 
 
+# image_path and measurement_interval_minutes are nullable columns where the
+# caller may deliberately want to clear the value (send null), not merely
+# leave it untouched by not mentioning the field at all. A plain
+# "getattr(...) is not None" check cannot tell those two cases apart -
+# once set, neither field could ever be cleared again (#37.3). The other
+# header fields keep that simpler check: booleans are always sent by the
+# client (never null) and clearing name/description to null is not a case
+# this endpoint needs to support.
+_NULLABLE_HEADER_FIELDS = ("image_path", "measurement_interval_minutes")
+
+
 def _header_fields(data: RecipeUpdate) -> dict:
-    """The header columns the caller actually asked to change."""
-    return {
-        field: getattr(data, field)
-        for field in HEADER_FIELDS
-        if getattr(data, field) is not None
-    }
+    """The header columns the caller actually asked to change.
+
+    For image_path/measurement_interval_minutes, "asked to change" includes
+    explicitly setting it to null - told apart from "field absent from the
+    request" via model_fields_set, since RecipeUpdate defaults both to None.
+    """
+    result = {}
+    for field in HEADER_FIELDS:
+        if field in _NULLABLE_HEADER_FIELDS:
+            if field in data.model_fields_set:
+                result[field] = getattr(data, field)
+        else:
+            value = getattr(data, field)
+            if value is not None:
+                result[field] = value
+    return result
 
 
 async def _get_recipe_or_404(db: AsyncSession, recipe_id: int) -> Recipe:

src/backend/tests/test_recipes.py

@@ -250,6 +250,79 @@ class TestUpdateRecipe:
         assert version_numbers == [1, 2]
 
 
+class TestUpdateRecipeClearNullableFields:
+    """gitea#37.3: measurement_interval_minutes/image_path, once set, could
+    never be cleared again - the request set them and the update endpoint
+    could not tell "not sent" apart from "sent as null" (both landed on the
+    same getattr(...) is not None check in recipe_service._header_fields)."""
+
+    async def test_explicit_null_clears_measurement_interval(
+        self, client: AsyncClient, maker_user: User, db_session: AsyncSession,
+    ):
+        recipe = await create_test_recipe(db_session, maker_user.id)
+
+        set_resp = await client.put(
+            f"/api/recipes/{recipe.id}",
+            headers=auth_headers(maker_user),
+            json={"measurement_interval_minutes": 30},
+        )
+        assert set_resp.status_code == 200
+        assert set_resp.json()["measurement_interval_minutes"] == 30
+
+        clear_resp = await client.put(
+            f"/api/recipes/{recipe.id}",
+            headers=auth_headers(maker_user),
+            json={"measurement_interval_minutes": None},
+        )
+        assert clear_resp.status_code == 200
+        assert clear_resp.json()["measurement_interval_minutes"] is None
+
+    async def test_explicit_null_clears_image_path(
+        self, client: AsyncClient, maker_user: User, db_session: AsyncSession,
+    ):
+        recipe = await create_test_recipe(db_session, maker_user.id)
+
+        set_resp = await client.put(
+            f"/api/recipes/{recipe.id}",
+            headers=auth_headers(maker_user),
+            json={"image_path": "uploads/1/1/preview.png"},
+        )
+        assert set_resp.status_code == 200
+        assert set_resp.json()["image_path"] == "uploads/1/1/preview.png"
+
+        clear_resp = await client.put(
+            f"/api/recipes/{recipe.id}",
+            headers=auth_headers(maker_user),
+            json={"image_path": None},
+        )
+        assert clear_resp.status_code == 200
+        assert clear_resp.json()["image_path"] is None
+
+    async def test_field_not_sent_leaves_existing_value_untouched(
+        self, client: AsyncClient, maker_user: User, db_session: AsyncSession,
+    ):
+        """Regression guard for the other half of the distinction: a request
+        that never mentions the field must still leave it as it was."""
+        recipe = await create_test_recipe(db_session, maker_user.id)
+
+        set_resp = await client.put(
+            f"/api/recipes/{recipe.id}",
+            headers=auth_headers(maker_user),
+            json={"measurement_interval_minutes": 45},
+        )
+        assert set_resp.status_code == 200
+        assert set_resp.json()["measurement_interval_minutes"] == 45
+
+        unrelated_resp = await client.put(
+            f"/api/recipes/{recipe.id}",
+            headers=auth_headers(maker_user),
+            json={"name": "Renamed Recipe"},
+        )
+        assert unrelated_resp.status_code == 200
+        assert unrelated_resp.json()["measurement_interval_minutes"] == 45
+        assert unrelated_resp.json()["name"] == "Renamed Recipe"
+
+
 class TestDeleteRecipe:
     """DELETE /api/recipes/{recipe_id} tests."""
 

src/frontend/flask_app/templates/maker/recipe_editor.html

@@ -556,10 +556,13 @@ function recipeEditor() {
         description: this.description.trim(),
       };
 
-      // Measurement interval
-      if (this.measurementIntervalMinutes) {
-        payload.measurement_interval_minutes = parseInt(this.measurementIntervalMinutes, 10);
-      }
+      // Measurement interval - always sent, explicit null when cleared
+      // (#37.3): omitting the key when the field was emptied used to leave
+      // the old value in place forever, because the backend could not tell
+      // "not sent" from "cleared".
+      payload.measurement_interval_minutes = this.measurementIntervalMinutes
+        ? parseInt(this.measurementIntervalMinutes, 10)
+        : null;
 
       // Rules of measurement. Sent every time, including when false: these are the
       // settings an operator gets told about, so turning one off has to travel.
@@ -567,10 +570,8 @@ function recipeEditor() {
       payload.requires_serial = !!this.requiresSerial;
       payload.allow_manual_input = !!this.allowManualInput;
 
-      // Include image_path for preview thumbnail
-      if (this.currentFilePath) {
-        payload.image_path = this.currentFilePath;
-      }
+      // image_path for preview thumbnail - same null-when-cleared rule (#37.3).
+      payload.image_path = this.currentFilePath || null;
 
       // Include change notes if editing
       if (!this.isNew && this.changeNotes.trim()) {