resource/aws_cognito_user_pool: Allow admin_create_user_config config…

…uration block unused_account_validity_days to be omitted (#12001)

Reference: #11858
Reference: #10890

There was previously no test configuration covering both admin_create_user_config and password_policy being defined. The upstream API has deprecated a field in the former, however if the configuration block was defined, the attribute would errantly show a difference on the deprecated field.

Previous output from acceptance testing (before code fix):

```
--- FAIL: TestAccAWSCognitoUserPool_withAdminCreateUserConfigurationAndPasswordPolicy (13.28s)
    testing.go:640: Step 0 error: After applying this step, the plan was not empty:

        DIFF:

        UPDATE: aws_cognito_user_pool.test
          admin_create_user_config.#:                              "1" => "1"
          admin_create_user_config.0.allow_admin_create_user_only: "true" => "true"
          admin_create_user_config.0.invite_message_template.#:    "0" => "0"
          admin_create_user_config.0.unused_account_validity_days: "7" => ""
... omitted for clarity ...
```

Output from acceptance testing:

```
--- PASS: TestAccAWSCognitoUserPool_withAdminCreateUserConfigurationAndPasswordPolicy (18.41s)
--- PASS: TestAccAWSCognitoUserPool_basic (18.46s)
--- PASS: TestAccAWSCognitoUserPool_withAliasAttributes (27.92s)
--- PASS: TestAccAWSCognitoUserPool_withPasswordPolicy (29.64s)
--- PASS: TestAccAWSCognitoUserPool_withVerificationMessageTemplate (29.68s)
--- PASS: TestAccAWSCognitoUserPool_withDeviceConfiguration (30.52s)
--- PASS: TestAccAWSCognitoUserPool_withEmailVerificationMessage (31.38s)
--- PASS: TestAccAWSCognitoUserPool_withSmsVerificationMessage (32.67s)
--- PASS: TestAccAWSCognitoUserPool_withSchemaAttributes (33.39s)
--- PASS: TestAccAWSCognitoUserPool_withAdminCreateUserConfiguration (37.94s)
--- PASS: TestAccAWSCognitoUserPool_withAdvancedSecurityMode (39.71s)
--- PASS: TestAccAWSCognitoUserPool_withTags (44.33s)
--- PASS: TestAccAWSCognitoUserPool_withSmsConfiguration (50.12s)
--- PASS: TestAccAWSCognitoUserPool_withSmsConfigurationUpdated (51.37s)
--- PASS: TestAccAWSCognitoUserPool_update (66.06s)
--- PASS: TestAccAWSCognitoUserPool_withLambdaConfig (75.15s)
```

aws/resource_aws_cognito_user_pool.go

@@ -67,6 +67,7 @@ func resourceAwsCognitoUserPool() *schema.Resource {
 						"unused_account_validity_days": {
 							Type:          schema.TypeInt,
 							Optional:      true,
+							Computed:      true,
 							Deprecated:    "Use password_policy.temporary_password_validity_days instead",
 							ValidateFunc:  validation.IntBetween(0, 90),
 							ConflictsWith: []string{"password_policy.0.temporary_password_validity_days"},

aws/resource_aws_cognito_user_pool_test.go

@@ -150,6 +150,33 @@ func TestAccAWSCognitoUserPool_withAdminCreateUserConfiguration(t *testing.T) {
 	})
 }
 
+// Reference: https://github.com/terraform-providers/terraform-provider-aws/issues/11858
+func TestAccAWSCognitoUserPool_withAdminCreateUserConfigurationAndPasswordPolicy(t *testing.T) {
+	name := acctest.RandomWithPrefix("tf-acc-test")
+	resourceName := "aws_cognito_user_pool.test"
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t); testAccPreCheckAWSCognitoIdentityProvider(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSCognitoUserPoolDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSCognitoUserPoolConfig_withAdminCreateUserConfigAndPasswordPolicy(name),
+				Check: resource.ComposeAggregateTestCheckFunc(
+					testAccCheckAWSCognitoUserPoolExists(resourceName),
+					resource.TestCheckResourceAttr(resourceName, "admin_create_user_config.0.allow_admin_create_user_only", "true"),
+					resource.TestCheckResourceAttr(resourceName, "password_policy.0.temporary_password_validity_days", "7"),
+				),
+			},
+			{
+				ResourceName:      resourceName,
+				ImportState:       true,
+				ImportStateVerify: true,
+			},
+		},
+	})
+}
+
 func TestAccAWSCognitoUserPool_withAdvancedSecurityMode(t *testing.T) {
 	name := acctest.RandString(5)
 	resourceName := "aws_cognito_user_pool.test"
@@ -1112,6 +1139,27 @@ resource "aws_cognito_user_pool" "test" {
 `, name)
 }
 
+func testAccAWSCognitoUserPoolConfig_withAdminCreateUserConfigAndPasswordPolicy(rName string) string {
+	return fmt.Sprintf(`
+resource "aws_cognito_user_pool" "test" {
+  name = %[1]q
+
+  admin_create_user_config {
+    allow_admin_create_user_only = true
+  }
+
+  password_policy {
+    minimum_length                   = 7
+    require_lowercase                = true
+    require_numbers                  = false
+    require_symbols                  = true
+    require_uppercase                = false
+    temporary_password_validity_days = 7
+  }
+}
+`, rName)
+}
+
 func testAccAWSCognitoUserPoolConfig_withPasswordPolicy(name string) string {
 	return fmt.Sprintf(`
 resource "aws_cognito_user_pool" "test" {