How can I add information from a config file when processing a yaml-file with CloudFormationCreateReplaceChangeSetAction?

Question

I have a pipeline with a source stage, build stage, and self-mutate stage. I'm trying to take an existing yaml file and prepare the project it's associated with for deployment. The yaml file uses a config file for production and a different for testing, which is why the code below produces the following error: `Parameters: [DatabaseNamespace, SecretsKmsKey] must have values (Service: AmazonCloudFormation; Status Code: 400; Error Code: ValidationError;`

I've been looking at the documentation [found here][1] and I think I'm close to figuring this out if I can pass the parameters from the config file with one of the props available.

The fourth stage of the pipeline:
```    pipeline.addStage({
      stageName: 'Test_Deploy',
      actions: [
        new CloudFormationCreateReplaceChangeSetAction({
          actionName: 'PrepareChanges',
          stackName: 'my-stack',
          changeSetName: 'StagedChangeSet',
          adminPermissions: true,
          templatePath: sourceOutput.atPath('cloudformation/cf-test.yaml'),
          runOrder: 1
        })
      ]
    })
```

Config file:
```
AppStackName=my-stack
AppDeployBucket=deploy-bucket
DatabaseNamespace=cf-test-database
SecretsKmsKey=secrets-kms-key
```

[1]: https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_codepipeline_actions.CloudFormationCreateReplaceChangeSetActionProps.html

Accepted Answer

You can directly provide the parameter values to the stack being deployed using the `parameterOverrides` attribute (see [the API documentation](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_codepipeline_actions.CloudFormationCreateReplaceChangeSetActionProps.html#parameteroverrides) for details).

```ts
new CloudFormationCreateReplaceChangeSetAction({
    actionName: 'PrepareChanges',
    stackName: 'my-stack',
    changeSetName: 'StagedChangeSet',
    adminPermissions: true,
    templatePath: sourceOutput.atPath('cloudformation/cf-test.yaml'),
    runOrder: 1,
    parameterOverrides: {
        'AppDeployBucket' : 'your-value',
        'DatabaseNamespace' : 'your-value'
    }
});
```
In the example above, the parameter names and values are hard-coded.

If you want to specify the parameters using an artifact file, use `templateConfiguration` instead ([documentation link](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_codepipeline_actions.CloudFormationCreateReplaceChangeSetActionProps.html#parameteroverrides)):

```ts
new CloudFormationCreateReplaceChangeSetAction({
    actionName: 'PrepareChanges',
    stackName: 'my-stack',
    changeSetName: 'StagedChangeSet',
    adminPermissions: true,
    templatePath: sourceOutput.atPath('cloudformation/cf-test.yaml'),
    runOrder: 1,
    templateConfiguration: sourceOutput.atPath('parameter-file.json'),
});
```
The template configuration file should contain a JSON object that should look like this: 
```json
{
    "Parameters": {...},
    "Tags": {...},
    "StackPolicy": {...}
}
```

How can I add information from a config file when processing a yaml-file with CloudFormationCreateReplaceChangeSetAction?

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