env-contract-check/README.md

Create a contract of environment varaibles for different environments.

# env-contract-check

Define and check contracts around environment varaibles.

The goal of this package is to make environment variables easy to check, default in development and enforce prsence in production.
While it is recommened to set NODE_ENV this package supports behaviours around an undefined NODE_ENV varaible.
This package attempts to balance convience for development with predictable desirable behaviour for deployment.

[![InstallSize](https://flat.badgen.net/packagephobia/install/env-contract-check/:subject/:status/:green)](https://packagephobia.now.sh/result?p=env-contract-check)

## Define Contract

```javascript
const ecc = require('env-contract-check');

// all boolean default false
// register accepts a single object or an array of objects
ecc.register([{
  name: 'MONGO_URL', // required
  optional: true,
  defaults: {
    development: 'mongo://localhost'
    docker: 'mongo://mongo',
    // production: 'mongo://mongo', // not recommend to set production default
  }  
  allowReregister: true // allow this contract to be redefined.
  log: true, // a console.log(name, value);
  hidden: true, // value of the env variable will not be printed to the console.
}]);
```

## Checking Environment

By default contracts first check to see if the environment varaible has been set.
If the varaible is missing the optional flag, defaults object and NODE_ENV are used to determine if the application should error.
It is best to set NODE_ENV but if missed this package defaults to 'development' or 'docker' if in a docker container.
Support for other process environments is a future goal.

### Strict NODE_ENV

A strict options requires NODE_ENV to be set forcing a process exit(1) if not set before requiring this package.

```javascript
ecc.strict()
```

## Setting the Environemnt

This package dose not provide a metheod of setting the environment with the excpetion of a defualt.
As hardcoding some environment variables is security problem an additional environment loader is recommened for efficient loading of the processes environment.
There are many great metheods for setting the process environment.
One recommendation is [dotenv](https://www.npmjs.com/package/dotenv) which is great for setting the process environment during development and dose not interfere with production process managers.
It is important to use any in process environment loader before requiring this package.

```javascript
// example using dotenv
require('dotenv').config()
// load env before ecc
const ecc = require('env-contract-check);
```

## Output

By default the only console output of this package is the state of NODE_ENV when being required.
There are two metheods to produce console output for other environemnt variables.
The first is to set `ecc.register({log: true})` which will print the name and value to the console.
The second is a sumamry that can be invoked printing a table of all current registered varaibles.

```javascript
ecc.summary()
```

## Dependancies

Dependancies that require env variable can safely use this package as well.
Again it is important to load the env before loading the any dependancies that will require this package.

## Reregister

To prevent unintentional overwriting if a varaible is registered twice the package will error.
This can be over writted by setting the `allowReregister` property to true of any duplicate register calls.

## Contributing

Issues, recommendations, and pull requests are welcome.