entc/gen: ensure foreign-key constraints are unique in codegen (#3066)

entc/gen/graph.go

@@ -681,6 +681,9 @@ func (g *Graph) Tables() (all []*schema.Table, err error) {
 			index.Annotation = entsqlIndexAnnotate(idx.Annotations)
 		}
 	}
+	if err := ensureUniqueFKs(tables); err != nil {
+		return nil, err
+	}
 	return
 }
 
@@ -733,6 +736,29 @@ func fkSymbols(e *Edge, c1, c2 *schema.Column) (string, string) {
 	return s1, s2
 }
 
+// ensureUniqueNames ensures constraint names are unique.
+func ensureUniqueFKs(tables map[string]*schema.Table) error {
+	fks := make(map[string]*schema.Table)
+	for _, t := range tables {
+		for _, fk := range t.ForeignKeys {
+			switch other, ok := fks[fk.Symbol]; {
+			case !ok:
+				fks[fk.Symbol] = t
+			case ok && other.Name != t.Name:
+				a, b := t.Name, other.Name
+				// Keep reporting order consistent.
+				if a > b {
+					a, b = b, a
+				}
+				return fmt.Errorf("duplicate foreign-key symbol %q found in tables %q and %q", fk.Symbol, a, b)
+			case ok:
+				return fmt.Errorf("duplicate foreign-key symbol %q found in table %q", fk.Symbol, t.Name)
+			}
+		}
+	}
+	return nil
+}
+
 // deleteAction returns the referential action for DELETE operations of the given edge.
 func deleteAction(e *Edge, c *schema.Column) schema.ReferenceOption {
 	action := schema.NoAction

entc/gen/graph_test.go

@@ -344,6 +344,40 @@ func TestFKColumns(t *testing.T) {
 	}
 }
 
+func TestAbortDuplicateFK(t *testing.T) {
+	var (
+		user = &load.Schema{
+			Name: "User",
+			Edges: []*load.Edge{
+				{Name: "pets", Type: "Pet", StorageKey: &edge.StorageKey{Symbols: []string{"owner_id"}}},
+				{Name: "cars", Type: "Car", StorageKey: &edge.StorageKey{Symbols: []string{"owner_id"}}},
+			},
+		}
+		pet = &load.Schema{
+			Name: "Pet",
+			Fields: []*load.Field{
+				{Name: "owner_id", Info: &field.TypeInfo{Type: field.TypeInt}, Nillable: true, Optional: true},
+			},
+			Edges: []*load.Edge{
+				{Name: "owner", Type: "User", RefName: "pets", Inverse: true, Unique: true},
+			},
+		}
+		car = &load.Schema{
+			Name: "Car",
+			Fields: []*load.Field{
+				{Name: "owner_id", Info: &field.TypeInfo{Type: field.TypeInt}, Nillable: true, Optional: true},
+			},
+			Edges: []*load.Edge{
+				{Name: "owner", Type: "User", RefName: "cars", Inverse: true, Unique: true},
+			},
+		}
+	)
+	g, err := NewGraph(&Config{Package: "entc/gen", Storage: drivers[0]}, user, pet, car)
+	require.NoError(t, err)
+	_, err = g.Tables()
+	require.EqualError(t, err, `duplicate foreign-key symbol "owner_id" found in tables "cars" and "pets"`)
+}
+
 func TestEnsureCorrectFK(t *testing.T) {
 	var (
 		user = &load.Schema{