Serverless-plugin-sandwich NPM

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Installation

npm install -D serverless-plugin-sandwich

yarn add -D serverless-plugin-sandwich

Usage

Plugin Dependency

In your projects serverless file, add serverless-plugin-sandwich to the list of your plugins:

plugins:
  - serverless-plugin-sandwich

Custom Declaration

`inline`

The function will be called inline, and not be tied to the original handler code. However, proper error handling needs to be taken into consideratioin.

functions:
  handler: src/original.default
  sandwich:
    before:
      handler: src/runFirst.default
      inline: true

Shorthand notation defaults to inline, and is declared the following way.

functions:
  handler: src/original.default
  sandwich:
    before: src/runFirst.default
    after: src/runAfter.default

`pipe`

The previous function pipes its output to the next function. Note, only one argument can be piped from function to function.

functions:
  handler: src/original.default
  sandwich:
    before:
      handler: src/extractData.default
      pipe: true

`wrap`

Higher-order-functions, that curry another function, can be useful for validating and extracting Authorization tokens. It could also be used for logging, or other boilerplate code that needs to be done before a lambda is called.

functions:
  handler: src/original.default
  sandwich:
    before:
      handler: src/extractData.default
      wrap: true

Code Generation

Sandwich dynamically changes the handler src path, and generates code for you. This definition:

functions:
  protected:
    handler: lambdas/wrapped/handler.default
    timeout: 30
    sandwich:
      before: 
        handler: lambdas/wrapped/authenticate.default
        wrap: true
      after: 
        handler: lambdas/wrapped/apiResponse.default
        pipe: true

Generates this code:

const before = require('../lambdas/wrapped/authenticate').default;
const handler = require('../lambdas/wrapped/handler').default;
const after = require('../lambdas/wrapped/apiResponse').default;

module.exports.default = async (event, context) => {

  const response = await after(await before(handler)(event, context));
  
  return response;
};