title: AWS CloudFormation: "Parameter [subnetIds] is invalid"
body: <p>I have a AWS CodePipeline to deploy a stack in CloudFormation using a YAML template as well as a template configuration JSON file. </p>
  
  <p><strong>Relevant Template Snippet:</strong></p>
  
  <pre><code>AWSTemplateFormatVersion: '2010-09-09'
  ...
  Parameters:
    subnetIds:
      Type: List&lt;AWS::EC2::Subnet::Id&gt;
  ...
  </code></pre>
  
  <p><strong>Relevant Configuration File Snippet:</strong></p>
  
  <pre><code>{
      "Parameters": {
        ...
        "subnetIds": [
          "subnet-a",
          "subnet-b",
          "subnet-c"
        ]
      },
      ...
  }
  </code></pre>
  
  <p>For some reason the Deploy stage (CloudFormation) keeps failing with <code>Parameter [subnetIds] is invalid</code>, so my question is how do I pass a list of subnetIds to the template from the configuration file?</p>