fix(iam): conditions in FederatedPrincipal should be optional (aws#20621

)

Fixes aws#11139

This PR makes conditions in `FederatedPrincipal` optional.

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packages/@aws-cdk/aws-iam/lib/principals.ts

@@ -604,19 +604,24 @@ export class CanonicalUserPrincipal extends PrincipalBase {
 export class FederatedPrincipal extends PrincipalBase {
   public readonly assumeRoleAction: string;
 
+  /**
+   * The conditions under which the policy is in effect.
+   * @see https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_condition.html
+   */
+  public readonly conditions: Conditions;
+
   /**
    *
    * @param federated federated identity provider (i.e. 'cognito-identity.amazonaws.com' for users authenticated through Cognito)
-   * @param conditions The conditions under which the policy is in effect.
-   *   See [the IAM documentation](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_condition.html).
    * @param sessionTags Whether to enable session tagging (see https://docs.aws.amazon.com/IAM/latest/UserGuide/id_session-tags.html)
    */
   constructor(
     public readonly federated: string,
-    public readonly conditions: Conditions,
+    conditions: Conditions = {},
     assumeRoleAction: string = 'sts:AssumeRole') {
     super();
 
+    this.conditions = conditions;
     this.assumeRoleAction = assumeRoleAction;
   }
 

packages/@aws-cdk/aws-iam/test/principals.test.ts

@@ -103,6 +103,19 @@ test('can have multiple principals the same conditions in the same statement', (
   }));
 });
 
+test('use federated principal', () => {
+  // GIVEN
+  const stack = new Stack();
+
+  // WHEN
+  const principal = new iam.FederatedPrincipal('federated');
+
+  // THEN
+  expect(stack.resolve(principal.federated)).toStrictEqual('federated');
+  expect(stack.resolve(principal.assumeRoleAction)).toStrictEqual('sts:AssumeRole');
+  expect(stack.resolve(principal.conditions)).toStrictEqual({});
+});
+
 test('use Web Identity principal', () => {
   // GIVEN
   const stack = new Stack();