resource/aws_cognito_identity_pool: Prevent ordering differences for …

…openid_connect_provider_arns argument (#15178)

Reference: #15176

Output from acceptance testing:

```
--- PASS: TestAccAWSCognitoIdentityPool_basic (24.04s)
--- PASS: TestAccAWSCognitoIdentityPool_supportedLoginProviders (31.68s)
--- PASS: TestAccAWSCognitoIdentityPool_cognitoIdentityProviders (32.20s)
--- PASS: TestAccAWSCognitoIdentityPool_tags (33.05s)
--- PASS: TestAccAWSCognitoIdentityPool_openidConnectProviderArns (33.34s)
--- PASS: TestAccAWSCognitoIdentityPool_samlProviderArns (37.66s)
```

aws/resource_aws_cognito_identity_pool.go

@@ -73,7 +73,7 @@ func resourceAwsCognitoIdentityPool() *schema.Resource {
 			},
 
 			"openid_connect_provider_arns": {
-				Type:     schema.TypeList,
+				Type:     schema.TypeSet,
 				Optional: true,
 				Elem: &schema.Schema{
 					Type:         schema.TypeString,
@@ -130,7 +130,7 @@ func resourceAwsCognitoIdentityPoolCreate(d *schema.ResourceData, meta interface
 	}
 
 	if v, ok := d.GetOk("openid_connect_provider_arns"); ok {
-		params.OpenIdConnectProviderARNs = expandStringList(v.([]interface{}))
+		params.OpenIdConnectProviderARNs = expandStringSet(v.(*schema.Set))
 	}
 
 	if v, ok := d.GetOk("tags"); ok {
@@ -221,7 +221,7 @@ func resourceAwsCognitoIdentityPoolUpdate(d *schema.ResourceData, meta interface
 	}
 
 	if v, ok := d.GetOk("openid_connect_provider_arns"); ok {
-		params.OpenIdConnectProviderARNs = expandStringList(v.([]interface{}))
+		params.OpenIdConnectProviderARNs = expandStringSet(v.(*schema.Set))
 	}
 
 	if v, ok := d.GetOk("saml_provider_arns"); ok {

website/docs/r/cognito_identity_pool.markdown

@@ -53,7 +53,7 @@ The Cognito Identity Pool argument layout is a structure composed of several sub
 * `developer_provider_name` (Optional) - The "domain" by which Cognito will refer to your users. This name acts as a placeholder that allows your
 backend and the Cognito service to communicate about the developer provider.
 * `cognito_identity_providers` (Optional) - An array of [Amazon Cognito Identity user pools](#cognito-identity-providers) and their client IDs.
-* `openid_connect_provider_arns` (Optional) - A list of OpendID Connect provider ARNs.
+* `openid_connect_provider_arns` (Optional) - Set of OpendID Connect provider ARNs.
 * `saml_provider_arns` (Optional) - An array of Amazon Resource Names (ARNs) of the SAML provider for your identity.
 * `supported_login_providers` (Optional) - Key-Value pairs mapping provider names to provider app IDs.
 * `tags` - (Optional) A map of tags to assign to the Identity Pool.