CloudFormation Review and Clean Up a Change Set

arazzo: 1.0.1
info:
  title: CloudFormation Review and Clean Up a Change Set
  summary: Create a change set, poll until it is computed, then branch — delete it when it contains no changes, otherwise keep it for review.
  description: >-
    A dry-run review flow that avoids leaving empty change sets behind. The
    workflow creates a change set, polls DescribeChangeSet until it finishes
    computing, and then branches on the result: when CloudFormation reports the
    change set failed because it contained no changes, the workflow deletes the
    useless change set; when real changes are present, it ends and leaves the
    change set in place for a human to review and execute. Every step spells out
    its request inline using the AWS query protocol so the flow can be read and
    executed without opening the underlying OpenAPI description.
  version: 1.0.0
sourceDescriptions:
- name: cloudformationApi
  url: ../openapi/cloudformation-api.yml
  type: openapi
workflows:
- workflowId: review-change-set
  summary: Create a change set for review and clean it up when it is empty.
  description: >-
    Creates a change set, waits for it to compute, and deletes it if it contains
    no changes; otherwise leaves it in place for review.
  inputs:
    type: object
    required:
    - stackName
    - changeSetName
    - templateBody
    properties:
      stackName:
        type: string
        description: The name or unique ID of the existing stack to review changes for.
      changeSetName:
        type: string
        description: The name to assign to the change set.
      templateBody:
        type: string
        description: The candidate CloudFormation template body to diff against the stack.
      capability:
        type: string
        description: An optional capability to acknowledge (e.g. CAPABILITY_IAM).
  steps:
  - stepId: createChangeSet
    description: >-
      Create a change set diffing the candidate template against the stack's
      current template.
    operationId: createChangeSet
    requestBody:
      contentType: application/x-www-form-urlencoded
      payload:
        StackName: $inputs.stackName
        ChangeSetName: $inputs.changeSetName
        TemplateBody: $inputs.templateBody
        ChangeSetType: UPDATE
        Capabilities:
        - $inputs.capability
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      changeSetId: $response.body#/CreateChangeSetResult/Id
  - stepId: pollChangeSet
    description: >-
      Poll DescribeChangeSet until it finishes computing. Branch to cleanup when
      it failed (typically because there were no changes), or end with the
      change set intact when real changes are present.
    operationId: describeChangeSet
    requestBody:
      contentType: application/x-www-form-urlencoded
      payload:
        ChangeSetName: $inputs.changeSetName
        StackName: $inputs.stackName
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      changeSetStatus: $response.body#/Status
      statusReason: $response.body#/StatusReason
      changes: $response.body#/Changes
    onSuccess:
    - name: hasChanges
      type: end
      criteria:
      - context: $response.body
        condition: $.Status == "CREATE_COMPLETE"
        type: jsonpath
    - name: noChanges
      type: goto
      stepId: deleteEmptyChangeSet
      criteria:
      - context: $response.body
        condition: $.Status == "FAILED"
        type: jsonpath
    - name: stillComputing
      type: goto
      stepId: pollChangeSet
      criteria:
      - context: $response.body
        condition: $.Status in ["CREATE_PENDING","CREATE_IN_PROGRESS"]
        type: jsonpath
  - stepId: deleteEmptyChangeSet
    description: >-
      Delete the empty or failed change set so it does not linger and risk being
      executed by mistake.
    operationId: deleteChangeSet
    requestBody:
      contentType: application/x-www-form-urlencoded
      payload:
        ChangeSetName: $inputs.changeSetName
        StackName: $inputs.stackName
    successCriteria:
    - condition: $statusCode == 200
  outputs:
    changeSetId: $steps.createChangeSet.outputs.changeSetId
    changeSetStatus: $steps.pollChangeSet.outputs.changeSetStatus
    changes: $steps.pollChangeSet.outputs.changes