fix(cfn-include): allow parameters to be replaced across nested stacks

Fixes #9838

Author: skinny85

packages/@aws-cdk/cloudformation-include/lib/cfn-include.ts

@@ -556,23 +556,31 @@ export class CfnInclude extends core.CfnElement {
 
     const nestedStackProps = cfnParser.parseValue(nestedStackAttributes.Properties);
     const nestedStack = new core.NestedStack(this, nestedStackId, {
-      parameters: nestedStackProps.Parameters,
+      parameters: this.parametersForNestedStack(nestedStackProps.Parameters, nestedStackId),
       notificationArns: nestedStackProps.NotificationArns,
       timeout: nestedStackProps.Timeout,
     });
+    const template = new CfnInclude(nestedStack, nestedStackId, this.nestedStacksToInclude[nestedStackId]);
+    this.nestedStacks[nestedStackId] = { stack: nestedStack, includedTemplate: template };
 
     // we know this is never undefined for nested stacks
     const nestedStackResource: core.CfnResource = nestedStack.nestedStackResource!;
     cfnParser.handleAttributes(nestedStackResource, nestedStackAttributes, nestedStackId);
+    return nestedStackResource;
+  }
 
-    const propStack = this.nestedStacksToInclude[nestedStackId];
-    const template = new CfnInclude(nestedStack, nestedStackId, {
-      templateFile: propStack.templateFile,
-      nestedStacks: propStack.nestedStacks,
-    });
-    const includedStack: IncludedNestedStack = { stack: nestedStack, includedTemplate: template };
-    this.nestedStacks[nestedStackId] = includedStack;
+  private parametersForNestedStack(parameters: any, nestedStackId: string): { [key: string]: any } | undefined {
+    if (parameters == null) {
+      return undefined;
+    }
 
-    return nestedStackResource;
+    const parametersToReplace = this.nestedStacksToInclude[nestedStackId].parameters ?? {};
+    const ret: { [key: string]: string } = {};
+    for (const paramName of Object.keys(parameters)) {
+      if (!(paramName in parametersToReplace)) {
+        ret[paramName] = parameters[paramName];
+      }
+    }
+    return ret;
   }
 }

packages/@aws-cdk/cloudformation-include/test/nested-stacks.test.ts

@@ -1,5 +1,5 @@
 import * as path from 'path';
-import { ResourcePart } from '@aws-cdk/assert';
+import { ABSENT, ResourcePart } from '@aws-cdk/assert';
 import '@aws-cdk/assert/jest';
 import * as s3 from '@aws-cdk/aws-s3';
 import * as core from '@aws-cdk/core';
@@ -9,7 +9,7 @@ import * as futils from '../lib/file-utils';
 /* eslint-disable quote-props */
 /* eslint-disable quotes */
 
-describe('CDK Include', () => {
+describe('CDK Include for nested stacks', () => {
   let stack: core.Stack;
 
   beforeEach(() => {
@@ -612,6 +612,66 @@ describe('CDK Include', () => {
       );
     });
   });
+
+  describe('for a parameter passed to the included child stack', () => {
+    let parentStack: core.Stack;
+    let childStack: core.Stack;
+
+    beforeAll(() => {
+      parentStack = new core.Stack();
+      const parentTemplate = new inc.CfnInclude(parentStack, 'ParentStack', {
+        templateFile: testTemplateFilePath('parent-two-parameters.json'),
+        nestedStacks: {
+          'ChildStack': {
+            templateFile: testTemplateFilePath('child-two-parameters.json'),
+            parameters: {
+              'FirstParameter': 'test-value',
+            },
+          },
+        },
+      });
+      childStack = parentTemplate.getNestedStack('ChildStack').stack;
+    });
+
+    test('correctly removes the parameter from the child stack', () => {
+      expect(childStack).toMatchTemplate({
+        "Parameters": {
+          "SecondParameter": {
+            "Type": "String",
+          },
+        },
+        "Resources": {
+          "BucketImport": {
+            "Type": "AWS::S3::Bucket",
+            "Properties": {
+              "BucketName": "test-value",
+              "AccessControl": {
+                "Ref": "SecondParameter",
+              },
+            },
+          },
+          "GrandChildStack": {
+            "Type": "AWS::CloudFormation::Stack",
+            "Properties": {
+              "TemplateURL": "https://cfn-templates-set.s3.amazonaws.com/grandchild-import-stack.json",
+              "Parameters": {
+                "FirstParameter": "test-value",
+              },
+            },
+          },
+        },
+      });
+    });
+
+    test('correctly removes the parameter from the parent stack', () => {
+      expect(parentStack).toHaveResourceLike('AWS::CloudFormation::Stack', {
+        "Parameters": {
+          "FirstParameter": ABSENT,
+          "SecondParameter": "second-value",
+        },
+      });
+    });
+  });
 });
 
 function loadTestFileToJsObject(testTemplate: string): any {

packages/@aws-cdk/cloudformation-include/test/test-templates/nested/child-two-parameters.json

@@ -0,0 +1,34 @@
+{
+  "Parameters": {
+    "FirstParameter": {
+      "Type": "String"
+    },
+    "SecondParameter": {
+      "Type": "String"
+    }
+  },
+  "Resources": {
+    "BucketImport": {
+      "Type": "AWS::S3::Bucket",
+      "Properties": {
+        "BucketName": {
+          "Ref": "FirstParameter"
+        },
+        "AccessControl": {
+          "Ref": "SecondParameter"
+        }
+      }
+    },
+    "GrandChildStack": {
+      "Type": "AWS::CloudFormation::Stack",
+      "Properties": {
+        "TemplateURL": "https://cfn-templates-set.s3.amazonaws.com/grandchild-import-stack.json",
+        "Parameters": {
+          "FirstParameter": {
+            "Ref": "FirstParameter"
+          }
+        }
+      }
+    }
+  }
+}

packages/@aws-cdk/cloudformation-include/test/test-templates/nested/parent-two-parameters.json

@@ -0,0 +1,14 @@
+{
+  "Resources": {
+    "ChildStack": {
+      "Type": "AWS::CloudFormation::Stack",
+      "Properties": {
+        "TemplateURL": "https://cfn-templates-set.s3.amazonaws.com/grandchild-import-stack.json",
+        "Parameters": {
+          "FirstParameter": "first-value",
+          "SecondParameter": "second-value"
+        }
+      }
+    }
+  }
+}