Media: Reset gallery modal state when abandoning a new gallery

src/js/media/views/frame/post.js

@@ -179,6 +179,7 @@ Post = Select.extend(/** @lends wp.media.view.MediaFrame.Post.prototype */{
 		Select.prototype.bindHandlers.apply( this, arguments );
 
 		this.on( 'activate', this.activate, this );
+		this.on( 'close', this.resetCreateGalleryState, this );
 
 		// Only bother checking media type counts if one of the counts is zero.
 		checkCounts = _.find( this.counts, function( type ) {
@@ -234,6 +235,30 @@ Post = Select.extend(/** @lends wp.media.view.MediaFrame.Post.prototype */{
 		}, this );
 	},
 
+	/**
+	 * Clears transient gallery state when a new gallery is abandoned.
+	 *
+	 * @since 7.1.0
+	 *
+	 * @return {void}
+	 */
+	resetCreateGalleryState: function() {
+		var state = this.state(),
+			edit;
+
+		if ( ! state || ! _.contains( [ 'gallery', 'gallery-edit', 'gallery-library' ], state.get( 'id' ) ) ) {
+			return;
+		}
+
+		edit = this.state( 'gallery-edit' );
+
+		if ( edit && ! edit.get( 'editing' ) ) {
+			edit.get( 'library' ).reset();
+			this.state( 'gallery' ).get( 'selection' ).reset();
+			this.state( 'gallery-library' ).get( 'selection' ).reset();
+		}
+	},
+
 	activate: function() {
 		// Hide menu items for states tied to particular media types if there are no items.
 		_.each( this.counts, function( type ) {

tests/qunit/index.html

@@ -162,6 +162,7 @@
 		<script src="wp-admin/js/customize-widgets.js"></script>
 		<script src="wp-admin/js/word-count.js"></script>
 		<script src="wp-admin/js/nav-menu.js"></script>
+		<script src="wp-admin/js/media/post-frame.js"></script>
 		<script src="wp-admin/js/widgets/test-media-widgets.js"></script>
 		<script src="wp-admin/js/widgets/test-media-image-widget.js"></script>
 		<script src="wp-admin/js/widgets/test-media-gallery-widget.js"></script>

tests/qunit/wp-admin/js/media/post-frame.js

@@ -0,0 +1,37 @@
+/* global wp */
+/* jshint qunit: true */
+/* eslint-env qunit */
+
+( function() {
+	'use strict';
+
+	QUnit.module( 'Media Frame Post' );
+
+	QUnit.test( 'closing an abandoned gallery clears transient gallery state', function( assert ) {
+		var frame = wp.media({
+				frame: 'post',
+				state: 'gallery',
+				multiple: true
+			}),
+			gallery = frame.state( 'gallery' ),
+			add = frame.state( 'gallery-library' ),
+			edit = frame.state( 'gallery-edit' ),
+			attachments = [
+				wp.media.model.Attachment.create( { id: 5748901, type: 'image' } ),
+				wp.media.model.Attachment.create( { id: 5748902, type: 'image' } )
+			];
+
+		gallery.get( 'selection' ).add( attachments );
+		add.get( 'selection' ).add( attachments );
+		edit.get( 'library' ).add( attachments );
+
+		frame.setState( 'gallery-edit' );
+		frame.trigger( 'close' );
+
+		assert.equal( edit.get( 'library' ).length, 0, 'The abandoned gallery selection is cleared.' );
+		assert.equal( gallery.get( 'selection' ).length, 0, 'The create-gallery selection is cleared.' );
+		assert.equal( add.get( 'selection' ).length, 0, 'The add-to-gallery selection is cleared.' );
+
+		frame.dispose();
+	} );
+}() );