Event: Use only one focusin/out handler per matching window & document

The `doc` variable in:
https://github.com/jquery/jquery/blob/3.4.1/src/event/focusin.js#L30
matched `document` for `document` & `window` for `window`, creating two
separate wrapper event handlers & calling handlers twice if at least one
`focusout` or `focusin` handler was attached on *both* `window` & `document`,
or on `window` & another regular node.

Also, fix the "focusin from an iframe" test to actually verify the behavior
from commit 1cecf64 - the commit that
introduced the regression - to make sure we don't regress on either front.

Fixes gh-4652
Closes gh-4656

src/event/focusin.js

@@ -27,7 +27,10 @@ if ( !support.focusin ) {
 
  jQuery.event.special[ fix ] = {
  setup: function() {
- var doc = this.ownerDocument || this,
+
+ // Handle: regular nodes (via `this.ownerDocument`), window
+ // (via `this.document`) & document (via `this`).
+ var doc = this.ownerDocument || this.document || this,
  attaches = dataPriv.access( doc, fix );
 
  if ( !attaches ) {
@@ -36,7 +39,7 @@ if ( !support.focusin ) {
  dataPriv.access( doc, fix, ( attaches || 0 ) + 1 );
  },
  teardown: function() {
- var doc = this.ownerDocument || this,
+ var doc = this.ownerDocument || this.document || this,
  attaches = dataPriv.access( doc, fix ) - 1;
 
  if ( !attaches ) {

test/unit/event.js

@@ -2555,31 +2555,66 @@ testIframe(
  function( assert, framejQuery, frameWin, frameDoc ) {
  assert.expect( 1 );
 
- var input = jQuery( frameDoc ).find( "#frame-input" );
+ var done = assert.async(),
+ focus = false,
+ input = jQuery( frameDoc ).find( "#frame-input" );
 
  // Create a focusin handler on the parent; shouldn't affect the iframe's fate
  jQuery( "body" ).on( "focusin.iframeTest", function() {
  assert.ok( false, "fired a focusin event in the parent document" );
  } );
 
  input.on( "focusin", function() {
+ focus = true;
  assert.ok( true, "fired a focusin event in the iframe" );
  } );
 
  // Avoid a native event; Chrome can't force focus to another frame
- input.trigger( "focusin" );
-
- // Must manually remove handler to avoid leaks in our data store
- input.remove();
-
- // Be sure it was removed; nothing should happen
- input.trigger( "focusin" );
+ input[ 0 ].focus();
 
  // Remove body handler manually since it's outside the fixture
  jQuery( "body" ).off( "focusin.iframeTest" );
+
+ setTimeout( function() {
+
+ // DOM focus is unreliable in TestSwarm
+ if ( QUnit.isSwarm && !focus ) {
+ assert.ok( true, "GAP: Could not observe focus change" );
+ }
+
+ done();
+ }, 50 );
  }
 );
 
+QUnit.test( "focusin on document & window", function( assert ) {
+ assert.expect( 1 );
+
+ var counter = 0,
+ input = jQuery( "<input />" );
+
+ input.appendTo( "#qunit-fixture" );
+
+ input[ 0 ].focus();
+
+ jQuery( window ).on( "focusout", function() {
+ counter++;
+ } );
+ jQuery( document ).on( "focusout", function() {
+ counter++;
+ } );
+
+ input[ 0 ].blur();
+
+ // DOM focus is unreliable in TestSwarm
+ if ( QUnit.isSwarm && counter === 0 ) {
+ assert.ok( true, "GAP: Could not observe focus change" );
+ }
+
+ assert.strictEqual( counter, 2,
+ "focusout handlers on document/window fired once only" );
+} );
+
 testIframe(
  "jQuery.ready promise",
  "event/promiseReady.html",