fix(s3-assets): throw if path property is empty (#29425)

### Issue # (if applicable)

Closes #29410.

### Reason for this change

It was reported that a `Code.fromAsset('')` was creating an infinite loop by including itself through `cdk.out`. This is caused by the following line:

https://github.com/aws/aws-cdk/blob/730fe63efc461c14f6e2b4aa9206c10f9b0f4cd9/packages/aws-cdk-lib/aws-s3-assets/lib/asset.ts#L145

If an empty string is given to `path.resolve()`, the current working directory is returned.

### Description of changes

I've added a check that verifies that the given `path` property is not empty.

### Description of how you validated changes

I've added a test for both the `aws-lambda` package, where the issue was originally reported, and `aws-s3-assets`, where the fix was implemented

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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

packages/aws-cdk-lib/aws-lambda/test/code.test.ts

@@ -16,6 +16,20 @@ describe('code', () => {
   });
 
   describe('lambda.Code.fromAsset', () => {
+    test('fails if path is empty', () => {
+      // GIVEN
+      const fileAsset = lambda.Code.fromAsset('');
+
+      // THEN
+      expect(() => defineFunction(fileAsset)).toThrow(/Asset path cannot be empty/);
+    });
+    test('fails if path does not exist', () => {
+      // GIVEN
+      const fileAsset = lambda.Code.fromAsset('/path/not/found/' + Math.random() * 999999);
+
+      // THEN
+      expect(() => defineFunction(fileAsset)).toThrow(/Cannot find asset/);
+    });
     test('fails if a non-zip asset is used', () => {
       // GIVEN
       const fileAsset = lambda.Code.fromAsset(path.join(__dirname, 'my-lambda-handler', 'index.py'));

packages/aws-cdk-lib/aws-s3-assets/lib/asset.ts

@@ -137,6 +137,10 @@ export class Asset extends Construct implements cdk.IAsset {
   constructor(scope: Construct, id: string, props: AssetProps) {
     super(scope, id);
 
+    if (!props.path) {
+      throw new Error('Asset path cannot be empty');
+    }
+
     this.isBundled = props.bundling != null;
 
     // stage the asset source (conditionally).

packages/aws-cdk-lib/aws-s3-assets/test/asset.test.ts

@@ -143,11 +143,18 @@ test('"readers" or "grantRead" can be used to grant read permissions on the asse
   });
 });
 
+test('fails if path is empty', () => {
+  const stack = new cdk.Stack();
+  expect(() => new Asset(stack, 'MyDirectory', {
+    path: '',
+  })).toThrow(/Asset path cannot be empty/);
+});
+
 test('fails if directory not found', () => {
   const stack = new cdk.Stack();
   expect(() => new Asset(stack, 'MyDirectory', {
     path: '/path/not/found/' + Math.random() * 999999,
-  })).toThrow();
+  })).toThrow(/Cannot find asset/);
 });
 
 test('multiple assets under the same parent', () => {