Detect ember-tether and throw an error early if not present and tetherTarget is passed.

README.md

@@ -278,6 +278,27 @@ This can then be used like so:
   Custom modal contents
 {{/full-screen-modal}}
 ```
+## Using as a nested addon
+
+If you create an addon that you want to depend on ember-modal-dialog, you need to provide for ember-modal-dialog's config hook to run. You do this in the config hook of your addon. Example:
+
+```js
+// index.js
+
+module.exports = {
+  name: 'my-addon',
+  config: function(environment, appConfig) {
+    let initialConfig = _.merge({}, appConfig);
+    let updatedConfig = this.addons.reduce((config, addon) => {
+      if (addon.config) {
+        _.merge(config, addon.config(environment, config));
+      }
+      return config;
+    }, initialConfig);
+    return updatedConfig;
+  }
+};
+```
 
 ## Dependencies
 

addon/components/modal-dialog.js

@@ -13,6 +13,9 @@ export default Ember.Component.extend({
     if (this.get('renderInPlace')) {
       return 'ember-modal-dialog/-in-place-dialog';
     } else if (this.get('tetherTarget')) {
+      if (!this.get('modalService.hasEmberTether')) {
+        throw new Error('Please install ember-tether in order to pass a tetherTarget to modal-dialog');
+      }
       return 'ember-modal-dialog/-tether-dialog';
     }
     return 'ember-modal-dialog/-basic-dialog';

app/services/modal-dialog.js

@@ -1,12 +1,16 @@
 import Ember from 'ember';
-import Service from 'ember-modal-dialog/services/modal-dialog';
 import ENV from '../config/environment';
 
-const {
-  computed
-} = Ember;
+const { computed, Service } = Ember;
+
+function computedFromConfig(prop) {
+  return computed(function(){
+    return ENV['ember-modal-dialog'][prop];
+  });
+}
 
 export default Service.extend({
+  hasEmberTether: computedFromConfig('hasEmberTether'),
   destinationElementId: computed(function() {
     /*
       everywhere except test, this property will be overwritten

config/environment.js

@@ -1,6 +1,15 @@
 /* eslint-env node */
 'use strict';
 
-module.exports = function(/* environment, appConfig */) {
-  return { };
+var VersionChecker = require('ember-cli-version-checker');
+
+module.exports = function( environment, appConfig, addon ) {
+  appConfig['ember-modal-dialog'] = appConfig['ember-modal-dialog'] || {};
+
+  var checker = new VersionChecker(addon);
+  var hasEmberTether = checker.for('ember-tether', 'npm').version;
+
+  appConfig['ember-modal-dialog']['hasEmberTether'] = hasEmberTether;
+
+  return appConfig;
 };

index.js

@@ -1,6 +1,19 @@
 /* eslint-env node */
 'use strict';
 
+var fs = require('fs');
+var path = require('path');
+
 module.exports = {
-  name: 'ember-modal-dialog'
+  name: 'ember-modal-dialog',
+  config: function (env, baseConfig) {
+    var configPath = path.join(this.root, 'config', 'environment.js');
+
+    if (fs.existsSync(configPath)) {
+      var configGenerator = require(configPath);
+
+      return configGenerator(env, baseConfig, this);
+    }
+  }
+
 };