Bug: `SqsRecordSchema` incorrectly precludes null value for `md5OfMessageAttributes`

[ajpower]

Expected Behavior

When an SQS queue's event source mapping is configured with a maxBatchingWindow, the md5OfMessageAttributes of the individual Records will be null. The SqsRecordSchema should parse such records.

Current Behavior

The SqsRecordSchema fails to parse records with null md5OfMessageAttributes, returning the error

Expected string, received null at "Records[0].md5OfMessageAttributes"

Code snippet

Create a Lambda handler using the S3SqsEventSchema defined below:

const S3TestEventSchema = z.object({
    Event: z.literal('s3:TestEvent'),
    Bucket: z.string(),
});
const S3EventRecordsSchema = S3Schema.transform((val) => val.Records[0]);
const S3EventSchema = z.union([S3EventRecordsSchema, S3TestEventSchema]);
const S3SqsEventRecordSchema = SqsRecordSchema.extend({
    body: JSONStringified(S3EventSchema),
});

export const S3SqsEventSchema = z.object({
    Records: z.array(S3SqsEventRecordSchema).nonempty(),
});

In our case, we are processing S3 events sent to an SQS queue. But the issue should be reproducible for any event type.

Steps to Reproduce

Create a Lambda function to process an SQS queue whose event source mapping includes a maxBatchingWindow.

Possible Solution

Allow md5OfMessageAttributes to be nullable:

md5OfMessageAttributes: z.string().optional().nullable(),

Powertools for AWS Lambda (TypeScript) version

latest

AWS Lambda function runtime

20.x

Packaging format used

npm

Execution logs

[sdangol]

Hi @ajpower, we are able to reproduce the issue. Let us get back to you after gathering some more information around this.