The update_function_configuration currently returns an empty dict no matter what but certain lambda libraries (ie, Zappa) require a realistic return value... which is simply the current config after being updated.

https://github.com/localstack/localstack/blob/9cba1010dfcbf2b7672df4d7da46b7e8ab287f64/localstack/services/awslambda/lambda_api.py#L872

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/lambda.html#Lambda.Client.update_function_configuration

There might also be some other magic enriching that result but my quick read-through looks like it's an empty dict.



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version = version or '$LATEST'
    func_version = func_details.get_version(version)
    result = {
        'CodeSha256': func_version.get('CodeSha256'),
        'Role': func_details.role,
        'Version': version,
        'FunctionArn': func_details.arn(),
        'FunctionName': func_details.name(),
        'CodeSize': func_version.get('CodeSize'),
        'Handler': func_details.handler,
        'Runtime': func_details.runtime,
        'Timeout': func_details.timeout,
        'Description': func_details.description,
        'MemorySize': func_details.memory_size,
        'LastModified': func_details.last_modified,
        'TracingConfig': {'Mode': 'PassThrough'},
        'RevisionId': func_version.get('RevisionId')
    }
    if func_details.envvars:
        result['Environment'] = {
            'Variables': func_details.envvars
        }
    if (always_add_version or version != '$LATEST') and len(result['FunctionArn'].split(':')) <= 7:
        result['FunctionArn'] += ':%s' % (version)
    return result
def forward_to_fallback_url(func_arn, data):