serverless-plugin-var-substitution

Serverless plugin to substitute variables in compiled cloudformation template

Add a variable substitution syntax so that serverless can maintain the normal syntax.

This is especially useful for stage variables in a swagger definition for Api Gateway.

...
custom:
    varSubstitution:
        pattern: '##'
        variables:
        - stageVariables.ConnectionId
        - search: something_random
          replace: something_more_random
Resources:
    ApiGatewayRestApi:
        Type: AWS::ApiGateway::Deployment
        Properties:
            Body:
                paths:
                    '/some/path':
                        get:
                            x-amazon-apigateway-integration:
                                connectionId: ##stageVariables.ConnectionId##
                                otherProperty: ##something_random##
...

You just need to specify a pattern and the variables you will replace. The default pattern is ##.

The plugin is run after the serverless package command is executed.

The parameters can be configured using the custom section in the serverless.yml file:

...
custom:
    varSubstitution:
        pattern: &&
        variables:
        - 'some string word'
        - search: 'some word'
          replace: 'some other word'
...

For the above example, the plugin would search for all occurences in the compiled CloudFormation template of &&some string word&& and replace them for ${some string word} and also all occurences of &&some word&& and replace them with some other word.

Getting Started

1. Install plugin from npm:

npm install --save-dev serverless-plugin-var-substitution

2. Add to the plugins section of your serverless.yml:

plugins:
  - serverless-plugin-var-substitution

3. Include variables in your CloudFormation templates.

Configuration

The plugin can be configured by setting the next parameters in the custom.varSubstitution object:

• pattern: String. The prefix and suffix that will be searched for. Defaults to '##'.

• variables: Array. The words that will be searched for to replace. Can be of 2 types:

  • String. Searches for the word and replaces it with ${word}

  varSubstitution:
      variables:
      - 'some word'  # transformed to ${some word}

  • Object. Searches for the word in the 'search' property and replaces it with the word in the replace property.

  varSubstitution:
      variables:
      - search: 'some word'  # transformed to 'some other word'
        replace: 'some other word'

More Info

Heavily influenced by serverless-plugin-time-substitution