Pass in style attribute to style attachment

addon/components/attach-popover.js

@@ -5,9 +5,10 @@ import { cancel, debounce, later, next, run } from '@ember/runloop';
 import { computed, observer } from '@ember/object';
 import { getOwner } from '@ember/application';
 import { guidFor } from '@ember/object/internals';
-import { htmlSafe } from '@ember/string';
+import { htmlSafe, isHTMLSafe } from '@ember/string';
 import { stripInProduction } from 'ember-attacher/-debug/helpers';
 import { warn } from '@ember/debug';
+import { isEmpty } from '@ember/utils';
 
 export default Component.extend({
   layout,
@@ -56,6 +57,7 @@ export default Component.extend({
   showDelay: DEFAULTS.showDelay,
   showDuration: DEFAULTS.showDuration,
   showOn: DEFAULTS.showOn,
+  style: DEFAULTS.style,
 
   /**
    * ================== PRIVATE IMPLEMENTATION DETAILS ==================
@@ -110,6 +112,18 @@ export default Component.extend({
     return `ember-attacher-${this.get('animation')} ${this.get('class') || ''} ${showOrHideClass}`;
   }),
 
+  _style: computed('style', '_transitionDuration', function () {
+    const style = this.get('style');
+    const transitionDuration = this.get('_transitionDuration');
+    warn(
+      '@ember/string/htmlSafe must be used for any `style` passed to ember-attacher',
+      isEmpty(style) || isHTMLSafe(style),
+      { id: 'ember-attacher-require-html-safe-style' }
+    );
+
+    return htmlSafe(`transition-duration: ${transitionDuration}ms; ${style}`);
+  }),
+
   // This is memoized so it can be used by both attach-popover and attach-tooltip
   _config: computed(function() {
     return getOwner(this).resolveRegistration('config:environment').emberAttacher || {};
@@ -206,10 +220,6 @@ export default Component.extend({
 
   _transitionDuration: 0,
 
-  _transitionDurationCss: computed('_transitionDuration', function() {
-    return htmlSafe(`transition-duration: ${this.get('_transitionDuration')}ms`);
-  }),
-
   /**
    * ================== LIFECYCLE HOOKS ==================
    */

addon/defaults.js

@@ -18,5 +18,6 @@ export default {
   showDelay: 0,
   showDuration: 300,
   showOn: 'mouseenter focus',
+  style: null,
   tooltipClass: 'ember-attacher-popper ember-attacher-tooltip'
 };

addon/templates/components/attach-popover.hbs

@@ -11,7 +11,7 @@
                   popperTarget=_currentTarget
                   registerAPI=(action 'registerAPI')
                   renderInPlace=renderInPlace as |emberPopper|}}
-    <div class="{{_class}}" style="{{_transitionDurationCss}}">
+    <div class="{{_class}}" style="{{_style}}">
       {{yield (hash emberPopper=emberPopper hide=(action 'hide'))}}
 
       {{#if arrow}}

tests/integration/components/attach-tooltip-test.js

@@ -3,6 +3,7 @@ import hbs from 'htmlbars-inline-precompile';
 import { find } from 'ember-native-dom-helpers';
 import { getOwner } from '@ember/application';
 import { moduleForComponent, test } from 'ember-qunit';
+import { htmlSafe } from '@ember/string';
 
 QUnit.assert.contains = function(actual, expected, message) {
   this.pushResult({
@@ -96,6 +97,45 @@ test('uses the user-supplied default tooltip class', function(assert) {
   );
 });
 
+test('uses style passed in by user', function (assert) {
+  this.set('style', htmlSafe('cursor: pointer;'));
+  this.render(hbs`
+    <div>
+      {{#attach-tooltip id='tooltip-with-style' style=style}}
+        tooltip text
+      {{/attach-tooltip}}
+    </div>
+
+    <div>
+      {{#attach-tooltip id='tooltip-with-no-style'}}
+        tooltip text
+      {{/attach-tooltip}}
+    </div>
+  `);
+
+  const tooltipWithStyle = find('#tooltip-with-style > .ember-attacher-tooltip');
+
+  assert.equal(
+    tooltipWithStyle.style.getPropertyValue('cursor'),
+    'pointer',
+    'it adds the user style to tooltips'
+  );
+
+  assert.equal(
+    tooltipWithStyle.style.getPropertyValue('transition-duration'),
+    '0ms',
+    'it adds the default style to tooltips'
+  );
+
+  const tooltipWithNoStyle = find('#tooltip-with-no-style > .ember-attacher-tooltip');
+
+  assert.equal(
+    tooltipWithNoStyle.style.getPropertyValue('transition-duration'),
+    '0ms',
+    'it adds the default style to tooltips with no user style'
+  );
+});
+
 test('adds aria-describedby to the target', function(assert) {
   this.set('showTooltip', true);