Supported `null` properties are removed from CloudFormation template

Discussed in https://github.com/serverless/serverless/discussions/10649

<div type='discussions-op-text'>

^{Originally posted by jack-c-tang February 7, 2022} Hi,

Based on the second note of the resource configuration document, the properties with null assignment are stripped before upload, because CloudFormation doesn’t allow them.

But CloudFormation template supports to include some transforms and macros that take those properties and transform to resources CFN allows. For example, AWS::Serverless is a transform CFN supports. The ResultPath specified in Definition property of AWS::Serverless::StateMachine resources accepts null value with certain purpose. Stripping them make the step functions not work as expected.

Should the strip function bypass resources that will be transformed? Or is there a better suggestion or workaround for this usage? Thanks.

Related PR: https://github.com/serverless/serverless/pull/10304 Related issue: https://github.com/serverless/serverless/issues/10279</div>

Example of a valid template, that hosts null values:

AWSTemplateFormatVersion: 2010-09-09
Description: Serverless transform resource with null assigned property
Transform: AWS::Serverless-2016-10-31
Resources:
  NullResultPathStateMachine:
    Type: AWS::Serverless::StateMachine
    Properties:
      Type: STANDARD
      Name: nullResultPathStateMachine
      Policies: arn:aws:iam::aws:policy/AWSStepFunctionsReadOnlyAccess
      Definition:
        StartAt: State1
        States:
          State1:
            Type: Pass
            Parameters:
              parameter: 'sample'
            ResultPath: null
            End: true

[shheo042]

Suffering same problem. ResultPath: null is stripped and the next state cannot receive input. Fix in https://github.com/serverless/serverless/pull/8975 might be stripping the supported null value. Is there any (temporary) workaround for this? I have to manually set ResultPath: null in AWS console currently.

[edmundcong]

any update on this? or possible workaround? the stripping of null means we can’t use ResultPath: null which is making our step function output exceed the 256k limit imposed by AWS