pending a pr to https://github.com/tunnckoCore/is-installed/issues/2

is-installed-README.md

Install

Install with npm:

$ npm install --save is-installed

Why use this?

• Useful for setup in unit tests, to conditionally install packages that aren't already installed.
• Useful for validating that a global CLI is installed, and that it satisfies a valid semver range (like gulp-cli etc)

Usage

var isInstalled = require('is-installed');

console.log(isInstalled('foo'));
//=> false

API

isInstalled

Returns true if npm package name is installed in node_modules relative to the user's current working directory.

Params

• name {String}: The name of the module to look for.
• cwd {String|Function}: Optionally specify a directory to start the search from, or a validation function.
• validate {Function}: Optionally specify a validation function to use as the last argument.
• returns {Boolean}

Example

isInstalled('gulp');

// or with a validation function
var semver = require('semver');
var installed = isInstalled('gulp', function(pkg) {
  return semver.gt(pkg.version, '0.1.0');
});

.global

Returns true if npm package name is installed in node_modules in the global npm directory.

Params

• name {String}: The name of the module to look for.
• cwd {String|Function}: Optionally specify a directory to start the search from, or a validation function.
• validate {Function}: Optionally specify a validation function to use as the last argument.
• returns {Boolean}

Example

isInstalled.global('gulp-cli');

// or with a validation function
var semver = require('semver');
var installed = isInstalled.global('gulp-cli', function(pkg) {
  return semver.gt(pkg.version, '0.1.0');
});

is-installed.js

'use strict';

var path = require('path');
var gm = require('global-modules');
var exists = require('fs-exists-sync');
var findPkg = require('find-pkg');
var extend = require('extend-shallow');

/**
 * Returns true if npm package `name` is installed in `node_modules` relative
 * to the user's current working directory.
 *
 * ```js
 * isInstalled('gulp');
 *
 * // or with a validation function
 * var semver = require('semver');
 * var installed = isInstalled('gulp', function(pkg) {
 *   return semver.gt(pkg.version, '0.1.0');
 * });
 * ```
 * @param {String} `name` The name of the module to look for.
 * @param {String|Function} `cwd` Optionally specify a directory to start the search from, or a validation function.
 * @param {Function} `validate` Optionally specify a validation function to use as the last argument.
 * @return {Boolean}
 * @api public
 */

function isInstalled(name, cwd, validate) {
  if (typeof cwd === 'function') {
    validate = cwd;
    cwd = null;
  }

  if (typeof cwd !== 'string') {
    var userPkg = findPkg.sync(process.cwd());
    cwd = userPkg ? path.dirname(userPkg) : process.cwd();
  }

  var mainPath = tryResolve(name, cwd);
  if (!mainPath) {
    return false;
  }

  var moduleDir = path.dirname(mainPath);
  if (mainPath && typeof validate === 'function') {
    var pkgPath = findPkg.sync(moduleDir);
    var pkg = pkgPath ? require(pkgPath) : null;
    return validate(pkg);
  }
  return true;
};

/**
 * Returns true if npm package `name` is installed in `node_modules` in the
 * global npm directory.
 *
 * ```js
 * isInstalled.global('gulp-cli');
 *
 * // or with a validation function
 * var semver = require('semver');
 * var installed = isInstalled.global('gulp-cli', function(pkg) {
 *   return semver.gt(pkg.version, '0.1.0');
 * });
 * ```
 * @param {String} `name` The name of the module to look for.
 * @param {String|Function} `cwd` Optionally specify a directory to start the search from, or a validation function.
 * @param {Function} `validate` Optionally specify a validation function to use as the last argument.
 * @return {Boolean}
 * @api public
 */

isInstalled.global = function(name, fn) {
  return isInstalled(name, gm, fn);
};

/**
 * Expose `isInstalled`
 */

module.exports = isInstalled;

/**
 * Try to resolve the path to the given module
 */

function tryResolve(name, cwd) {
  try {
    return require.resolve(name);
  } catch (err) {}
  try {
    return require.resolve(path.resolve(cwd, name));
  } catch (err) {}
  return null;
}

test.js

'use strict';

require('mocha');
var assert = require('assert');
var npm = require('npm-install-global');
var isInstalled = require('./');
var semver = require('semver');

describe('is-installed', function() {
  before(function(cb) {
    if (!isInstalled.global('mocha')) {
      npm.install('mocha', cb);
    } else {
      cb();
    }
  });

  describe('api', function() {
    it('should export a function', function() {
      assert.equal(typeof isInstalled, 'function');
    });

    it('should expose a `.global` method', function() {
      assert.equal(typeof isInstalled.global, 'function');
    });
  });

  describe('isInstalled', function() {
    it('should return true if a package is installed locally', function() {
      assert(isInstalled('mocha'));
    });

    it('should return false if a package is not installed locally', function() {
      assert(!isInstalled('fosososos'));
    });

    it('should return true if the module exists and the validation function returns true', function() {
      var installed = isInstalled('mocha', function(pkg) {
        return semver.gt(pkg.version, '0.1.0');
      });
      assert(installed);
    });

    it('should return false if the module exists but the validation function returns false', function() {
      var installed = isInstalled('mocha', function(pkg) {
        return semver.gt(pkg.version, '1000.1.0');
      });
      assert(!installed);
    });
  });

  describe('isInstalled.global', function() {
    it('should return true if a package is installed locally', function() {
      assert(isInstalled.global('mocha'));
    });

    it('should return false if a package is not installed locally', function() {
      assert(!isInstalled.global('fosososos'));
    });

    it('should return true if the module exists and the validation function returns true', function() {
      var installed = isInstalled.global('mocha', function(pkg) {
        return semver.gt(pkg.version, '0.1.0');
      });
      assert(installed);
    });

    it('should return false if the module exists but the validation function returns false', function() {
      var installed = isInstalled.global('mocha', function(pkg) {
        return semver.gt(pkg.version, '1000.1.0');
      });
      assert(!installed);
    });
  });
});