Fill: refuse an empty rectangle; list plops whose plant is gone unnamed

A blank region name with a zero-area Region reached hexCenters, whose
tiny-region rule plants one plop in the middle — a caller that said nothing
about where got a plop at the centre. ListObjectPlantings also failed the whole
listing if one plop's plant no longer existed; it now lists that plop unnamed.

Co-Authored-By: Claude Fable 5 <[email protected]>

internal/service/ops.go

@@ -218,6 +218,10 @@ func (s *Service) Fill(ctx context.Context, actorID, objectID int64, spec FillSp
 		if region, err = NamedRegion(o, spec.RegionName); err != nil {
 			return nil, err
 		}
+	} else if !(region.MinX < region.MaxX && region.MinY < region.MaxY) {
+		// A zero or inverted rectangle is a caller that said nothing about where
+		// — not a request for the one plop hexCenters would put at its middle.
+		return nil, fmt.Errorf("%w: the fill rectangle is empty", domain.ErrInvalidInput)
 	}
 	return s.fillLoaded(ctx, actorID, o, region, spec)
 }
@@ -673,11 +677,13 @@ func (s *Service) ListObjectPlantings(ctx context.Context, actorID, objectID int
 		plant, ok := plants[pl.PlantID]
 		if !ok {
 			p, err := s.store.GetPlant(ctx, pl.PlantID)
-			if err != nil {
+			if err != nil && !errors.Is(err, domain.ErrNotFound) {
 				return nil, err
 			}
-			plant = *p
-			plants[pl.PlantID] = plant
+			if p != nil {
+				plant = *p
+			}
+			plants[pl.PlantID] = plant // a plant that no longer exists lists unnamed, not as an error
 		}
 		pl.DerivedCount = derivedCount(pl.RadiusCM, plant.SpacingCM)
 		out = append(out, describePlanting(pl, plant.Name))

internal/service/ops_test.go

@@ -790,4 +790,11 @@ func TestFillByRectangleAttributesSeed(t *testing.T) {
 	if _, err := s.Fill(ctx, owner, bed.ID, FillSpec{RegionName: "all", PlantID: garlic.ID, SeedLotID: &lot.ID}); err == nil {
 		t.Error("a fill charged to a lot of a different plant succeeded")
 	}
+	// No name and no rectangle is "nowhere", not "one plop in the middle" (which
+	// is what hexCenters makes of a zero-area region).
+	for _, r := range []Region{{}, {MinX: 10, MinY: -10, MaxX: 10, MaxY: 10}, {MinX: 20, MinY: 0, MaxX: -20, MaxY: 10}} {
+		if _, err := s.Fill(ctx, owner, bed.ID, FillSpec{Region: r, PlantID: garlic.ID}); !errors.Is(err, domain.ErrInvalidInput) {
+			t.Errorf("empty rectangle %+v: err = %v, want ErrInvalidInput", r, err)
+		}
+	}
 }