neat-contract

neat-contract

yet another one contract library, data flow focused

If contract is satisfied, returns value, otherwise, throwing TypeError exception. Well suited for promises as well.

Install

npm install --save neat-contract

Usage

• Basic
• Data-flow
  • Sync data-flow
  • Async data-flow
  • Arrays in data-flow

Basic

import contract from 'neat-contract';

contract('input', String, 'unicorns'); // 'unicorns'
contract('input', String, 2); // new TypeError('`input` should be an `String`, but got `Number`: 2')

// several types
contract('input', [String, Array], 'unicorns'); // 'unicorns'
contract('input', [String, Array], ['unicorns']); // ['unicorns']
contract('input', [String, Array], 2); // new TypeError('`input` should be an `String|Array`, but got `Number`: 2')

// curried
contract('input', String)('unicorns'); // 'unicorns'
contract('input', String)(2); // new TypeError('`input` should be an `String`, but got `Number`: 2')

// contracting array
contract(input, Array, ['unicorns', 'cats']); // ['unicorns', 'cats']
contract(input, Array, 2); // new TypeError('`input` should be an `Array`, but got `Number`: 2')
['unicorns', 'cats'].forEach(contract('input[item]', String)); // ['unicorns', 'cats']
['unicorns', 2].forEach(contract('input[item]', String)); // new TypeError('`input[item]` should be an `String`, but got `Number`: 2')

Data-flow

Sync data-flow

import R from 'ramda';
import contract from 'neat-contract';

// sync data flow
const prefixEslintPlugin = R.pipe(
  contract('pluginName', String), // contracting
  R.concat('eslint-plugin-')
);

prefixEslintPlugin('import'); // 'eslint-plugin-import'
prefixEslintPlugin(true);  // new TypeError('`pluginName` should be an `String`, but got `Boolean`: true')
prefixEslintPlugin(/reg/); // new TypeError('`pluginName` should be an `String`, but got `RegExp`: /reg/')

Async data-flow

import R from 'ramda';
import contract from 'neat-contract';

// helpers
const toPromise = Promise.resolve.bind(Promise);
const _log = console.log.bind(console);
const _throw = err => { throw err; };

// async data flow
const prefixEslintPluginAsync = R.pipeP(toPromise,
  contract('pluginName', String), // contracting
  R.concat('eslint-plugin-')
);

prefixEslintPluginAsync('import').then(_log); // 'eslint-plugin-import'
prefixEslintPluginAsync(true).catch(_throw);  // new TypeError('`pluginName` should be an `String`, but got `Boolean`: true')
prefixEslintPluginAsync(/reg/).catch(_throw); // new TypeError('`pluginName` should be an `String`, but got `RegExp`: /reg/')

Arrays in data-flow

import R from 'ramda';
import contract from 'neat-contract';

// contracting array
const prefixArrayOfEslintPlugins = R.pipe(
  R.pipe( // contracting in 2 steps
    contract('plugins', Array), // array itself
    R.map(contract('plugins[item]', String)) // each item of array
  ),
  R.map(R.concat('eslint-plugin-'))
);

prefixArrayOfEslintPlugins(['import', 'export']); // ['eslint-plugin-import', 'eslint-plugin-export']
prefixArrayOfEslintPlugins(2); // throw new TypeError('`plugins` should be an `Array`, but got `Number`: 2')
prefixArrayOfEslintPlugins(['unicorns', 2]); // throw new TypeError('`plugins[item]` should be an `String`, but got `Number`: 2')

Contracting arrays in asynchronous functions goes, the same way as in async example from above.

API

contract(name, ctor, param)

// contract :: String -> Constructor -> a -> a|throw new TypeError

name

Required
Type: String

Parameter name.

ctor

Required
Type: Constructor
Example: String, Number or Function

Parameter Constructor for type check

param

Required
Type: any

Actual parameter itself to type check with Constructor.

License

MIT © Vladimir Starkov