From e2386c5d4aea564a1e03d90be88ea578afe7c25b Mon Sep 17 00:00:00 2001
From: Addison Stavlo <Stavz01@gmail.com>
Date: Fri, 8 May 2020 16:12:42 -0400
Subject: [PATCH] Gallery block / media-placeholder - Preserve changes made
 while upload in progress. (#19134)

* added optional prop to pass by reference instead of value

* currentValue updated on adding/removing

* comment update

* fixed multiple upload bug

* removed stuff for trying to keep loaders that werent part of the upload group

* updates comments and naming

* updated galleryValue to fallback to empty array

* renamed values to be more semantic

* removed dynamicAlteration prop

* refactored to compare last pass of newMedia

* added comments, changed variable name

* simplified setting lastMediaPassed

* compare via includes instead

* added id check as first priority in filter

* edited comments

* rebased

* changed to soft equal for int/string ID comparison

* added unchanging reference for image array

* re-added fallback value for currentMedia, fixed linter == problem

* updated comment

* re-added addToGallery check, forced 'true' for our gallery

* refactored to use a getValue instead

* updated comment

* Remove getValue and use a reference to this.props.value

* comment update

Co-authored-by: Jorge <jorge.costa@developer.pt>
---
 .../src/components/media-placeholder/index.js | 42 +++++++++++++++++--
 packages/block-library/src/gallery/edit.js    |  5 +--
 2 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/packages/block-editor/src/components/media-placeholder/index.js b/packages/block-editor/src/components/media-placeholder/index.js
index 505464b7264b2e..5e62dfd47ea782 100644
--- a/packages/block-editor/src/components/media-placeholder/index.js
+++ b/packages/block-editor/src/components/media-placeholder/index.js
@@ -116,14 +116,50 @@ export class MediaPlaceholder extends Component {
 			multiple,
 			onError,
 			onSelect,
-			value = [],
 		} = this.props;
 		let setMedia;
 		if ( multiple ) {
 			if ( addToGallery ) {
-				const currentValue = value;
+				// To allow changes to a gallery to be made while uploads are in progress
+				// (including trigging multiple upload groups and removing already in place images),
+				// we must be able to add newMedia based on the current value of the Gallery
+				// whenever the setMedia function runs (not destructuring 'value' from props).
+				// Additionally, since the setMedia function runs multiple times per upload group
+				// and is passed newMedia containing every item in its group each time, we must
+				// also filter out whatever this upload group had previously returned to the
+				// gallery before adding and returning the image array with replacement newMedia
+				// values.
+
+				// Define an array to store urls from newMedia between subsequent function calls.
+				let lastMediaPassed = [];
 				setMedia = ( newMedia ) => {
-					onSelect( currentValue.concat( newMedia ) );
+					// Remove any images this upload group is responsible for (lastMediaPassed).
+					// Their replacements are contained in newMedia.
+					const filteredMedia = ( this.props.value || [] ).filter(
+						( item ) => {
+							// If Item has id, only remove it if lastMediaPassed has an item with that id.
+							if ( item.id ) {
+								return ! lastMediaPassed.some(
+									// Be sure to convert to number for comparison.
+									( { id } ) =>
+										Number( id ) === Number( item.id )
+								);
+							}
+							// Compare transient images via .includes since gallery may append extra info onto the url.
+							return ! lastMediaPassed.some( ( { urlSlug } ) =>
+								item.url.includes( urlSlug )
+							);
+						}
+					);
+					// Return the filtered media array along with newMedia.
+					onSelect( filteredMedia.concat( newMedia ) );
+					// Reset lastMediaPassed and set it with ids and urls from newMedia.
+					lastMediaPassed = newMedia.map( ( media ) => {
+						// Add everything up to '.fileType' to compare via .includes.
+						const cutOffIndex = media.url.lastIndexOf( '.' );
+						const urlSlug = media.url.slice( 0, cutOffIndex );
+						return { id: media.id, urlSlug };
+					} );
 				};
 			} else {
 				setMedia = onSelect;
diff --git a/packages/block-library/src/gallery/edit.js b/packages/block-library/src/gallery/edit.js
index 3f77212f71990a..cac649205b0b72 100644
--- a/packages/block-library/src/gallery/edit.js
+++ b/packages/block-library/src/gallery/edit.js
@@ -355,11 +355,10 @@ class GalleryEdit extends Component {
 		} = attributes;
 
 		const hasImages = !! images.length;
-		const hasImagesWithId = hasImages && some( images, ( { id } ) => id );
 
 		const mediaPlaceholder = (
 			<MediaPlaceholder
-				addToGallery={ hasImagesWithId }
+				addToGallery={ true }
 				isAppender={ hasImages }
 				className={ className }
 				disableMediaButtons={ hasImages && ! isSelected }
@@ -372,7 +371,7 @@ class GalleryEdit extends Component {
 				accept="image/*"
 				allowedTypes={ ALLOWED_MEDIA_TYPES }
 				multiple
-				value={ hasImagesWithId ? images : undefined }
+				value={ images }
 				onError={ this.onUploadError }
 				notices={ hasImages ? undefined : noticeUI }
 				onFocus={ this.props.onFocus }