Upgrade Plugin to new API

.eslintrc

@@ -0,0 +1,102 @@
+{
+  "env": {
+    "jasmine": true,
+    "node": true,
+    "mocha": true,
+    "browser": true,
+    "builtin": true
+  },
+  ecmaVersion: 7,
+  "globals":
+    {"Ember":true,
+    "jQuery":true,
+    "$":true,
+    "RSVP":true,
+    "Discourse":true,
+    "Em":true,
+    "PreloadStore":true,
+    "Handlebars":true,
+    "I18n":true,
+    "bootbox":true,
+    "module":true,
+    "moduleFor":true,
+    "moduleForComponent":true,
+    "Pretender":true,
+    "sandbox":true,
+    "controllerFor":true,
+    "test":true,
+    "ok":true,
+    "not":true,
+    "expect":true,
+    "equal":true,
+    "visit":true,
+    "andThen":true,
+    "click":true,
+    "currentPath":true,
+    "currentRouteName":true,
+    "currentURL":true,
+    "fillIn":true,
+    "keyEvent":true,
+    "triggerEvent":true,
+    "count":true,
+    "exists":true,
+    "visible":true,
+    "invisible":true,
+    "asyncRender":true,
+    "selectDropdown":true,
+    "asyncTestDiscourse":true,
+    "fixture":true,
+    "find":true,
+    "sinon":true,
+    "moment":true,
+    "start":true,
+    "_":true,
+    "alert":true,
+    "containsInstance":true,
+    "deepEqual":true,
+    "notEqual":true,
+    "define":true,
+    "require":true,
+    "requirejs":true,
+    "hasModule":true,
+    "Blob":true,
+    "File":true},
+  "rules": {
+    "block-scoped-var": 2,
+    "dot-notation": 0,
+    "eqeqeq": [
+      2,
+      "allow-null"
+    ],
+    "guard-for-in": 2,
+    "no-bitwise": 2,
+    "no-caller": 2,
+    "no-cond-assign": 0,
+    "no-debugger": 2,
+    "no-empty": 0,
+    "no-eval": 2,
+    "no-extend-native": 2,
+    "no-extra-parens": 0,
+    "no-irregular-whitespace": 2,
+    "no-iterator": 2,
+    "no-loop-func": 2,
+    "no-multi-str": 2,
+    "no-new": 2,
+    "no-plusplus": 0,
+    "no-proto": 2,
+    "no-script-url": 2,
+    "no-sequences": 2,
+    "no-shadow": 2,
+    "no-undef": 2,
+    "no-unused-vars": 2,
+    "no-with": 2,
+    "semi": 2,
+    "strict": 0,
+    "valid-typeof": 2,
+    "wrap-iife": [
+      2,
+      "inside"
+    ]
+  },
+  "parser": "babel-eslint"
+}

assets/javascripts/discourse/initializers/extend-for-signatures.js.es6

@@ -1,12 +1,36 @@
 import Post from 'discourse/models/post';
-import User from 'discourse/models/user';
+import { withPluginApi } from 'discourse/lib/plugin-api';
+
+function oldPluginCode() {
+  Post.reopen({
+    showSignatures: function() {
+      return Discourse.User.currentProp("custom_fields.see_signatures");
+    }.property()
+  });
+}
+
+function attachSignature(api) {
+  api.includePostAttributes('user_signature_url');
+
+  api.decorateWidget('post-contents:after', (h, attrs) => {
+    if (Ember.isEmpty(attrs.user_signature_url)) { return; }
+
+    const currentUser = api.getCurrentUser();
+    if (currentUser) {
+      const enabled = currentUser.get('custom_fields.see_signatures');
+      if (enabled) {
+        return [h('hr'), h('img.signature-img', { attributes: { src: attrs.user_signature_url } } )];
+      }
+    }
+  });
+}
 
 export default {
   name: 'extend-for-signatures',
-  initialize() {
-
-    Post.reopen({
-      showSignatures: Discourse.SiteSettings.signatures_enabled && Discourse.User.currentProp("custom_fields.see_signatures")
-    });
+  initialize(container) {
+    const siteSettings = container.lookup('site-settings:main');
+    if (siteSettings.signatures_enabled) {
+      withPluginApi('0.1', attachSignature, { noApi: oldPluginCode });
+    }
   }
 };