schema: Make validation more strict

helper/schema/resource.go

@@ -244,7 +244,20 @@ func (r *Resource) InternalValidate(topSchemaMap schemaMap) error {
 				return fmt.Errorf(
 					"No Update defined, must set ForceNew on: %#v", nonForceNewAttrs)
 			}
+		} else {
+			nonUpdateableAttrs := make([]string, 0)
+			for k, v := range r.Schema {
+				if v.ForceNew || (v.Computed && !v.Optional) {
+					nonUpdateableAttrs = append(nonUpdateableAttrs, k)
+				}
+			}
+			updateableAttrs := len(r.Schema) - len(nonUpdateableAttrs)
+			if updateableAttrs == 0 {
+				return fmt.Errorf(
+					"All fields are ForceNew or Computed w/out Optional, Update is superfluous")
+			}
 		}
+
 		tsm = schemaMap(r.Schema)
 	}
 

helper/schema/resource_test.go

@@ -335,6 +335,36 @@ func TestResourceInternalValidate(t *testing.T) {
 			},
 			true,
 		},
+
+		// Update undefined for non-ForceNew field
+		{
+			&Resource{
+				Create: func(d *ResourceData, meta interface{}) error { return nil },
+				Schema: map[string]*Schema{
+					"boo": &Schema{
+						Type:     TypeInt,
+						Optional: true,
+					},
+				},
+			},
+			true,
+		},
+
+		// Update defined for ForceNew field
+		{
+			&Resource{
+				Create: func(d *ResourceData, meta interface{}) error { return nil },
+				Update: func(d *ResourceData, meta interface{}) error { return nil },
+				Schema: map[string]*Schema{
+					"goo": &Schema{
+						Type:     TypeInt,
+						Optional: true,
+						ForceNew: true,
+					},
+				},
+			},
+			true,
+		},
 	}
 
 	for i, tc := range cases {