Add .exists() and document .version.

README.md

@@ -1,13 +1,40 @@
-### Ember CLI Version Checker
+# Ember CLI Version Checker
 
 [![npm version](https://badge.fury.io/js/ember-cli-version-checker.svg)](https://badge.fury.io/js/ember-cli-version-checker)
 [![Build Status](https://travis-ci.org/ember-cli/ember-cli-version-checker.svg?branch=master)](https://travis-ci.org/ember-cli/ember-cli-version-checker)
 
 Makes it easier to determine if a compatible version of a given NPM or Bower package is present.
 
-### Usage
+## Usage
 
-#### assertAbove
+Example:
+
+You want to provide two different sets of templates, based on the currently running Ember version.
+
+```javascript
+let path = require('path');
+let VersionChecker = require('ember-cli-version-checker');
+
+module.exports = {
+  name: 'awesome-addon',
+  treeForAddonTemplates(tree) {
+    let checker = new VersionChecker(this);
+    let dep = checker.for('ember', 'bower');
+
+    let baseTemplatesPath = path.join(this.root, 'addon/templates');
+
+    if (dep.satisfies('>= 1.13.0') {
+      return this.treeGenerator(path.join(baseTemplatesPath, 'current'));
+    } else {
+      return this.treeGenerator(path.join(baseTemplatesPath, 'legacy'));
+    }
+  }
+};
+```
+
+## API
+
+### assertAbove
 
 Throws an error with the given message if a minimum version isn't met.
 
@@ -41,7 +68,7 @@ module.exports = {
 };
 ```
 
-#### isAbove
+### isAbove
 
 Returns `true` if the packages version is above the specified comparison range.
 
@@ -63,50 +90,68 @@ module.exports = {
 };
 ```
 
-#### Real World Example
+### forEmber
 
-You want to provide two different sets of templates, based on the currently running Ember version.
+Since ember introduced the `ember-source` from NPM, ember has two ways to be
+shipped. One from bower `ember` and other from NPM `ember-source`. The
+function `forEmber` will look for `ember-source` from NPM, if it doesn't
+find it, it will look for `ember` in bower.
 
 ```javascript
-let path = require('path');
 let VersionChecker = require('ember-cli-version-checker');
 
 module.exports = {
   name: 'awesome-addon',
-  treeForAddonTemplates(tree) {
+  init() {
     let checker = new VersionChecker(this);
-    let dep = checker.for('ember', 'bower');
-
-    let baseTemplatesPath = path.join(this.root, 'addon/templates');
+    let ember = checker.forEmber();
 
-    if (dep.satisfies('>= 1.13.0') {
-      return this.treeGenerator(path.join(baseTemplatesPath, 'current'));
-    } else {
-      return this.treeGenerator(path.join(baseTemplatesPath, 'legacy'));
-    }
+    if (ember.isAbove('2.10.0')) {
+      /* deal with 2.10.0 stuff */
+    };
   }
 };
 ```
 
-#### forEmber
+### exists
 
-Since ember introduced the `ember-source` from NPM, ember has two ways to be
-shipped. One from bower `ember` and other from NPM `ember-source`. The
-function `forEmber` will look for `ember-source` from NPM, if it doesn't
-find it, it will look for `ember` in bower.
+Returns `true` or `false` indicating if the dependency exists (at any version).
 
-```javascript
+```js
 let VersionChecker = require('ember-cli-version-checker');
 
 module.exports = {
   name: 'awesome-addon',
   init() {
+    this._super.init.apply(this, arguments);
+
     let checker = new VersionChecker(this);
-    let ember = checker.forEmber();
+    let dep = checker.for('ember-cli-qunit');
 
-    if (ember.isAbove('2.10.0')) {
-      /* deal with 2.10.0 stuff */
+    if (dep.exists()) {
+      /* do things when present */
     };
   }
 };
 ```
+
+### version
+
+A property that returns the version for the dependency, if the dependency is not found
+`undefined` will be returned.
+
+```js
+let VersionChecker = require('ember-cli-version-checker');
+
+module.exports = {
+  name: 'awesome-addon',
+  init() {
+    this._super.init.apply(this, arguments);
+
+    let checker = new VersionChecker(this);
+    let dep = checker.for('ember-cli-qunit');
+
+    // do something with dep.version
+  }
+};
+```

src/dependency-version-checker.js

@@ -36,6 +36,10 @@ class DependencyVersionChecker {
     return this._version;
   }
 
+  exists() {
+    return this.version !== undefined;
+  }
+
   isAbove(compareVersion) {
     if (!this.version) {
       return false;

src/version-checker.js

@@ -1,6 +1,6 @@
 'use strict';
 
-const path = require('path');
+/* eslint-env node */
 
 const BowerDependencyVersionChecker = require('./bower-dependency-version-checker');
 const NPMDependencyVersionChecker = require('./npm-dependency-version-checker');

tests/index.js

@@ -1,5 +1,7 @@
 'use strict';
 
+/* eslint-env mocha, node */
+
 const assert = require('assert');
 const VersionChecker = require('..');
 const co = require('co');
@@ -136,6 +138,20 @@ describe('ember-cli-version-checker', function() {
       });
     });
 
+    describe('exists', function() {
+      it('returns true when present', function() {
+        let thing = checker.for('ember');
+
+        assert.ok(thing.exists());
+      });
+
+      it('returns false when not present', function() {
+        let thing = checker.for('rando-thing-here');
+
+        assert.ok(!thing.exists());
+      });
+    });
+
     describe('version', function() {
       it('can return a bower version', function() {
         let thing = checker.for('ember', 'bower');