AWS SAM template automated embedding of environment variables using the Doppler CLI and a Node.js script

.gitignore

template-deploy.yaml

deploy-template.js

import fs from 'fs';
import { execSync } from 'child_process'

let environmentTemplate =`Environment:
        Variables:`

const template = fs.readFileSync('template.yaml', { encoding: 'utf-8'})
const secrets = JSON.parse(execSync('doppler secrets download --no-file', { encoding: 'utf-8'}).toString())

Object.keys(secrets).forEach( key => {
    environmentTemplate += `\n          ${key}: ${secrets[key]}`
})

console.log(template.replace('#$ENVIRONMENT', environmentTemplate))

package.json

{
  "type": "module",
  "scripts": {
    "deploy-template": "node deploy-template.js > template-deploy.yaml",
    "local-dev": "node deploy-template.js > template-deploy.yaml; sam local start-api --template template-deploy.yaml; rm template-deploy.yaml",
    "deploy": "node deploy-template.js > template-deploy.yaml; sam deploy --template template-deploy.yaml; rm template-deploy.yaml;" 
  }
}

template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: >
  sam-app

  Sample SAM Template for sam-app
  
# More info about Globals: https://github.com/awslabs/serverless-application-model/blob/master/docs/globals.rst
Globals:
  Function:
    Timeout: 3

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction
    Properties:
      CodeUri: hello-world/
      Handler: app.lambdaHandler
      Runtime: nodejs14.x
      #$ENVIRONMENT
      Events:
        HelloWorld:
          Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
          Properties:
            Path: /hello
            Method: get

Outputs:
  # ServerlessRestApi is an implicit API created out of Events key under Serverless::Function
  # Find out more about other implicit resources you can reference within SAM
  # https://github.com/awslabs/serverless-application-model/blob/master/docs/internals/generated_resources.rst#api
  HelloWorldApi:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/hello/"
  HelloWorldFunction:
    Description: "Hello World Lambda Function ARN"
    Value: !GetAtt HelloWorldFunction.Arn
  HelloWorldFunctionIamRole:
    Description: "Implicit IAM Role created for Hello World function"
    Value: !GetAtt HelloWorldFunctionRole.Arn