fix(cognito-identitypool): providerUrl causes error when mappingKey is not provided and it is a token

packages/@aws-cdk/aws-cognito-identitypool/README.md

@@ -270,7 +270,7 @@ new IdentityPool(this, 'myidentitypool', {
 });
 ```
 
-Using a rule-based approach to role mapping allows roles to be assigned based on custom claims passed from the identity  provider:
+Using a rule-based approach to role mapping allows roles to be assigned based on custom claims passed from the identity provider:
 
 ```ts
 import { IdentityPoolProviderUrl, RoleMappingMatchType } from '@aws-cdk/aws-cognito-identitypool';
@@ -349,6 +349,25 @@ new IdentityPool(this, 'myidentitypool', {
 });
 ```
 
+If a provider URL is a CDK Token, as it will be if you are trying to use a previously defined Cognito User Pool, you will need to also provide a mappingKey.
+This is because by default, the key in the Cloudformation role mapping hash is the providerUrl, and Cloudformation map keys must be concrete strings, they
+cannot be references. For example:
+
+```ts
+import { UserPool } from '@aws-cdk/aws-cognito';
+import { IdentityPoolProviderUrl } from '@aws-cdk/aws-cognito-identitypool';
+
+declare const userPool : UserPool;
+new IdentityPool(this, 'myidentitypool', {
+  identityPoolName: 'myidentitypool',
+  roleMappings: [{
+    mappingKey: 'cognito',
+    providerUrl: IdentityPoolProviderUrl.userPool(userPool.userPoolProviderUrl),
+    useToken: true,
+  }],
+});
+```
+
 See [here](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-cognito-identitypoolroleattachment-rolemapping.html#cfn-cognito-identitypoolroleattachment-rolemapping-identityprovider) for more information.
 
 ### Authentication Flow

packages/@aws-cdk/aws-cognito-identitypool/lib/identitypool-role-attachment.ts

@@ -7,6 +7,7 @@ import {
 import {
   Resource,
   IResource,
+  Token,
 } from '@aws-cdk/core';
 import {
   Construct,
@@ -65,6 +66,12 @@ export interface IdentityPoolRoleMapping {
    */
   readonly providerUrl: IdentityPoolProviderUrl;
 
+  /**
+   * The key used for the role mapping in the role mapping hash. Required if the providerUrl is a token.
+   * @default - the provided providerUrl
+   */
+  readonly mappingKey?: string;
+
   /**
    *  If true then mapped roles must be passed through the cognito:roles or cognito:preferred_role claims from identity provider.
    * @see https://docs.aws.amazon.com/cognito/latest/developerguide/role-based-access-control.html#using-tokens-to-assign-roles-to-users
@@ -176,6 +183,17 @@ export class IdentityPoolRoleAttachment extends Resource implements IIdentityPoo
   ): { [name:string]: CfnIdentityPoolRoleAttachment.RoleMappingProperty } | undefined {
     if (!props || !props.length) return undefined;
     return props.reduce((acc, prop) => {
+      let mappingKey;
+      if (prop.mappingKey) {
+        mappingKey = prop.mappingKey;
+      } else {
+        const providerUrl = prop.providerUrl.value;
+        if (Token.isUnresolved(providerUrl)) {
+          throw new Error('mappingKey must be provided when providerUrl.value is an unresolved token');
+        }
+        mappingKey = providerUrl;
+      }
+
       let roleMapping: any = {
         ambiguousRoleResolution: prop.resolveAmbiguousRoles ? 'AuthenticatedRole' : 'Deny',
         type: prop.useToken ? 'Token' : 'Rules',
@@ -196,7 +214,7 @@ export class IdentityPoolRoleAttachment extends Resource implements IIdentityPoo
           }),
         };
       };
-      acc[prop.providerUrl.value] = roleMapping;
+      acc[mappingKey] = roleMapping;
       return acc;
     }, {} as { [name:string]: CfnIdentityPoolRoleAttachment.RoleMappingProperty });
   }

packages/@aws-cdk/aws-cognito-identitypool/test/identitypool.integ.snapshot/integ-identitypool.template.json

@@ -399,6 +399,20 @@
        "Arn"
       ]
      }
+    },
+    "RoleMappings": {
+     "www.amazon.com": {
+      "AmbiguousRoleResolution": "Deny",
+      "IdentityProvider": "www.amazon.com",
+      "Type":"Token"
+     },
+     "theKey":{
+      "AmbiguousRoleResolution": "Deny",
+      "IdentityProvider": {
+       "Fn::ImportValue": "ProviderUrl"
+      },
+      "Type":"Token"
+     }
     }
    },
    "DependsOn": [

packages/@aws-cdk/aws-cognito-identitypool/test/identitypool.test.ts

@@ -18,6 +18,7 @@ import {
   PolicyDocument,
 } from '@aws-cdk/aws-iam';
 import {
+  Fn,
   Stack,
 } from '@aws-cdk/core';
 import {
@@ -397,6 +398,93 @@ describe('identity pool', () => {
 });
 
 describe('role mappings', () => {
+  test('mappingKey respected when identity provider is not a token', () => {
+    const stack = new Stack();
+    new IdentityPool(stack, 'TestIdentityPoolRoleMappingToken', {
+      roleMappings: [{
+        mappingKey: 'amazon',
+        providerUrl: IdentityPoolProviderUrl.AMAZON,
+        useToken: true,
+      }],
+    });
+    Template.fromStack(stack).hasResourceProperties('AWS::Cognito::IdentityPoolRoleAttachment', {
+      IdentityPoolId: {
+        Ref: 'TestIdentityPoolRoleMappingToken0B11D690',
+      },
+      RoleMappings: {
+        amazon: {
+          AmbiguousRoleResolution: 'Deny',
+          IdentityProvider: 'www.amazon.com',
+          Type: 'Token',
+        },
+      },
+      Roles: {
+        authenticated: {
+          'Fn::GetAtt': [
+            'TestIdentityPoolRoleMappingTokenAuthenticatedRoleD99CE043',
+            'Arn',
+          ],
+        },
+        unauthenticated: {
+          'Fn::GetAtt': [
+            'TestIdentityPoolRoleMappingTokenUnauthenticatedRole1D86D800',
+            'Arn',
+          ],
+        },
+      },
+    });
+  });
+
+  test('mappingKey required when identity provider is not a token', () => {
+    const stack = new Stack();
+    const providerUrl = Fn.importValue('ProviderUrl');
+    expect(() => new IdentityPool(stack, 'TestIdentityPoolRoleMappingErrors', {
+      roleMappings: [{
+        providerUrl: IdentityPoolProviderUrl.userPool(providerUrl),
+        useToken: true,
+      }],
+    })).toThrowError('mappingKey must be provided when providerUrl.value is an unresolved token');
+  });
+
+  test('mappingKey respected when identity provider is a token', () => {
+    const stack = new Stack();
+    const providerUrl = Fn.importValue('ProviderUrl');
+    new IdentityPool(stack, 'TestIdentityPoolRoleMappingToken', {
+      roleMappings: [{
+        mappingKey: 'theKey',
+        providerUrl: IdentityPoolProviderUrl.userPool(providerUrl),
+        useToken: true,
+      }],
+    });
+    Template.fromStack(stack).hasResourceProperties('AWS::Cognito::IdentityPoolRoleAttachment', {
+      IdentityPoolId: {
+        Ref: 'TestIdentityPoolRoleMappingToken0B11D690',
+      },
+      RoleMappings: {
+        theKey: {
+          AmbiguousRoleResolution: 'Deny',
+          IdentityProvider: {
+            'Fn::ImportValue': 'ProviderUrl',
+          },
+          Type: 'Token',
+        },
+      },
+      Roles: {
+        authenticated: {
+          'Fn::GetAtt': [
+            'TestIdentityPoolRoleMappingTokenAuthenticatedRoleD99CE043',
+            'Arn',
+          ],
+        },
+        unauthenticated: {
+          'Fn::GetAtt': [
+            'TestIdentityPoolRoleMappingTokenUnauthenticatedRole1D86D800',
+            'Arn',
+          ],
+        },
+      },
+    });
+  });
   test('using token', () => {
     const stack = new Stack();
     new IdentityPool(stack, 'TestIdentityPoolRoleMappingToken', {

packages/@aws-cdk/aws-cognito-identitypool/test/integ.identitypool.ts

@@ -10,10 +10,12 @@ import {
 } from '@aws-cdk/aws-iam';
 import {
   App,
+  Fn,
   Stack,
 } from '@aws-cdk/core';
 import {
   IdentityPool,
+  IdentityPoolProviderUrl,
 } from '../lib/identitypool';
 import {
   UserPoolAuthenticationProvider,
@@ -56,6 +58,17 @@ const idPool = new IdentityPool(stack, 'identitypool', {
     amazon: { appId: 'amzn1.application.12312k3j234j13rjiwuenf' },
     google: { clientId: '12345678012.apps.googleusercontent.com' },
   },
+  roleMappings: [
+    {
+      providerUrl: IdentityPoolProviderUrl.AMAZON,
+      useToken: true,
+    },
+    {
+      mappingKey: 'theKey',
+      providerUrl: IdentityPoolProviderUrl.userPool(Fn.importValue('ProviderUrl')),
+      useToken: true,
+    },
+  ],
   allowClassicFlow: true,
   identityPoolName: 'my-id-pool',
 });