feat(core): add validations for export name in CfnOutput (#28575)

Closes #28563.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: go-to-k

packages/aws-cdk-lib/cloudformation-include/test/valid-templates.test.ts

@@ -727,7 +727,7 @@ describe('CDK Include', () => {
     const output = cfnTemplate.getOutput('Output1');
     output.value = 'a mutated value';
     output.description = undefined;
-    output.exportName = 'an export';
+    output.exportName = 'an-export';
     output.condition = new core.CfnCondition(stack, 'MyCondition', {
       expression: core.Fn.conditionIf('AlwaysFalseCond', core.Aws.NO_VALUE, true),
     });
@@ -755,7 +755,7 @@ describe('CDK Include', () => {
         "Output1": {
           "Value": "a mutated value",
           "Export": {
-            "Name": "an export",
+            "Name": "an-export",
           },
           "Condition": "MyCondition",
         },

packages/aws-cdk-lib/core/lib/cfn-output.ts

@@ -178,10 +178,19 @@ export class CfnOutput extends CfnElement {
   }
 
   private validateOutput(): string[] {
-    if (this._exportName && !Token.isUnresolved(this._exportName) && this._exportName.length > 255) {
-      return [`Export name cannot exceed 255 characters (got ${this._exportName.length} characters)`];
+    const errors: string[] = [];
+    if (this._exportName !== undefined && !Token.isUnresolved(this._exportName)) {
+      if (this._exportName.length === 0) {
+        errors.push('Export name cannot be empty');
+      }
+      if (this._exportName.length > 255) {
+        errors.push(`Export name cannot exceed 255 characters (got ${this._exportName.length} characters)`);
+      }
+      if (!/^[A-Za-z0-9-:]*$/.test(this._exportName)) {
+        errors.push(`Export name must only include alphanumeric characters, colons, or hyphens (got '${this._exportName}')`);
+      }
     }
-    return [];
+    return errors;
   }
 }
 

packages/aws-cdk-lib/core/test/output.test.ts

@@ -140,7 +140,44 @@ describe('output', () => {
     const errors = output.node.validate();
 
     expect(errors).toEqual([
-      expect.stringContaining('Export name cannot exceed 255 characters'),
+      expect.stringContaining('Export name cannot exceed 255 characters (got 260 characters)'),
+    ]);
+  });
+
+  test('Verify zero length of export name', () => {
+    const output = new CfnOutput(stack, 'SomeOutput', { value: 'x', exportName: '' });
+    const errors = output.node.validate();
+
+    expect(errors).toEqual([
+      expect.stringContaining('Export name cannot be empty'),
+    ]);
+  });
+
+  test('throw if export name has invalid strings (space)', () => {
+    const output = new CfnOutput(stack, 'SomeOutput', { value: 'x', exportName: 'SOME INVALID EXPORT NAME' });
+    const errors = output.node.validate();
+
+    expect(errors).toEqual([
+      expect.stringContaining('Export name must only include alphanumeric characters, colons, or hyphens (got \'SOME INVALID EXPORT NAME\''),
+    ]);
+  });
+
+  test('throw if export name has invalid strings (underscore)', () => {
+    const output = new CfnOutput(stack, 'SomeOutput', { value: 'x', exportName: 'SOME_INVALID_EXPORT_NAME' });
+    const errors = output.node.validate();
+
+    expect(errors).toEqual([
+      expect.stringContaining('Export name must only include alphanumeric characters, colons, or hyphens (got \'SOME_INVALID_EXPORT_NAME\''),
+    ]);
+  });
+
+  test('throw if export name exceeds maximum length and has invalid strings', () => {
+    const output = new CfnOutput(stack, 'SomeOutput', { value: 'x', exportName: ' '.repeat(260) });
+    const errors = output.node.validate();
+
+    expect(errors).toEqual([
+      expect.stringContaining('Export name cannot exceed 255 characters (got 260 characters)'),
+      expect.stringContaining(`Export name must only include alphanumeric characters, colons, or hyphens (got '${' '.repeat(260)}'`),
     ]);
   });
 });