allow TestCheckNoResourceAttr for empty containers

Stricter type handling in the new shims may add empty containers into
the state where they were previously elided. Since the detection of
missing and empty containers in the legacy state was never reliable,
allow TestCheckNoResourceAttr to succeed if the key is a container count
index, and the value is "0"

helper/resource/testing.go

@@ -1026,7 +1026,20 @@ func TestCheckModuleNoResourceAttr(mp []string, name string, key string) TestChe
 }
 
 func testCheckNoResourceAttr(is *terraform.InstanceState, name string, key string) error {
-	if _, ok := is.Attributes[key]; ok {
+	// Empty containers may sometimes be included in the state.
+	// If the intent here is to check for an empty container, allow the value to
+	// also be "0".
+	emptyCheck := false
+	if strings.HasSuffix(key, ".#") || strings.HasSuffix(key, ".%") {
+		emptyCheck = true
+	}
+
+	val, exists := is.Attributes[key]
+	if emptyCheck && val == "0" {
+		return nil
+	}
+
+	if exists {
 		return fmt.Errorf("%s: Attribute '%s' found when not expected", name, key)
 	}
 

helper/resource/testing_test.go

@@ -1144,3 +1144,34 @@ func TestCheckResourceAttr_empty(t *testing.T) {
 		})
 	}
 }
+
+func TestCheckNoResourceAttr_empty(t *testing.T) {
+	s := terraform.NewState()
+	s.AddModuleState(&terraform.ModuleState{
+		Path: []string{"root"},
+		Resources: map[string]*terraform.ResourceState{
+			"test_resource": &terraform.ResourceState{
+				Primary: &terraform.InstanceState{
+					Attributes: map[string]string{
+						"empty_list.#": "0",
+						"empty_map.%":  "0",
+					},
+				},
+			},
+		},
+	})
+
+	for _, key := range []string{
+		"empty_list.#",
+		"empty_map.%",
+		"missing_list.#",
+		"missing_map.%",
+	} {
+		t.Run(key, func(t *testing.T) {
+			check := TestCheckNoResourceAttr("test_resource", key)
+			if err := check(s); err != nil {
+				t.Fatal(err)
+			}
+		})
+	}
+}