From e816e71902a70c59e16aef208a03b60562b1aa88 Mon Sep 17 00:00:00 2001
From: epiqueras <epiquerass@gmail.com>
Date: Sun, 15 Sep 2019 14:41:01 -0400
Subject: [PATCH] Core Data: Fix undo approach.

---
 package-lock.json                          |  1 +
 packages/block-editor/src/store/reducer.js |  4 +--
 packages/core-data/package.json            |  1 +
 packages/core-data/src/reducer.js          | 39 ++++++++++------------
 4 files changed, 20 insertions(+), 25 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 6997ac51ebbd9..e22853f36d83e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -4885,6 +4885,7 @@
 				"@wordpress/api-fetch": "file:packages/api-fetch",
 				"@wordpress/data": "file:packages/data",
 				"@wordpress/deprecated": "file:packages/deprecated",
+				"@wordpress/is-shallow-equal": "file:packages/is-shallow-equal",
 				"@wordpress/url": "file:packages/url",
 				"equivalent-key-map": "^0.2.2",
 				"lodash": "^4.17.14",
diff --git a/packages/block-editor/src/store/reducer.js b/packages/block-editor/src/store/reducer.js
index 69dcbf65d72e2..9f40684c6632d 100644
--- a/packages/block-editor/src/store/reducer.js
+++ b/packages/block-editor/src/store/reducer.js
@@ -381,9 +381,7 @@ function withPersistentBlockChange( reducer ) {
 		// In comparing against the previous action, consider only those which
 		// would have qualified as one which would have been ignored or not
 		// have resulted in a changed state.
-		if ( ! isExplicitPersistentChange ) {
-			lastAction = action;
-		}
+		lastAction = action;
 
 		return nextState;
 	};
diff --git a/packages/core-data/package.json b/packages/core-data/package.json
index bc485ead098ed..3da791a43f81c 100644
--- a/packages/core-data/package.json
+++ b/packages/core-data/package.json
@@ -26,6 +26,7 @@
 		"@wordpress/api-fetch": "file:../api-fetch",
 		"@wordpress/data": "file:../data",
 		"@wordpress/deprecated": "file:../deprecated",
+		"@wordpress/is-shallow-equal": "file:../is-shallow-equal",
 		"@wordpress/url": "file:../url",
 		"equivalent-key-map": "^0.2.2",
 		"lodash": "^4.17.14",
diff --git a/packages/core-data/src/reducer.js b/packages/core-data/src/reducer.js
index 48c3a6da889e8..68c3ff7e51f13 100644
--- a/packages/core-data/src/reducer.js
+++ b/packages/core-data/src/reducer.js
@@ -7,6 +7,7 @@ import { keyBy, map, groupBy, flowRight, isEqual, get } from 'lodash';
  * WordPress dependencies
  */
 import { combineReducers } from '@wordpress/data';
+import isShallowEqual from '@wordpress/is-shallow-equal';
 
 /**
  * Internal dependencies
@@ -322,32 +323,26 @@ export function undo( state = UNDO_INITIAL_STATE, action ) {
 				return nextState;
 			}
 
-			let nextState;
-			if ( state.length === 0 ) {
-				// Create an initial entry so that we can undo to it.
-				nextState = [
-					{
-						kind: action.meta.undo.kind,
-						name: action.meta.undo.name,
-						recordId: action.meta.undo.recordId,
-						edits: { ...state.flattenedUndo, ...action.meta.undo.edits },
-					},
-				];
-				nextState.offset = 0;
-				return nextState;
-			}
-
 			// Clear potential redos, because this only supports linear history.
-			nextState = state.slice( 0, state.offset || undefined );
+			const nextState = state.slice( 0, state.offset || undefined );
 			nextState.offset = 0;
-
+			nextState.pop();
 			nextState.push( {
-				kind: action.kind,
-				name: action.name,
-				recordId: action.recordId,
-				edits: { ...action.edits, ...state.flattenedUndo },
+				kind: action.meta.undo.kind,
+				name: action.meta.undo.name,
+				recordId: action.meta.undo.recordId,
+				edits: { ...state.flattenedUndo, ...action.meta.undo.edits },
 			} );
-
+			const comparisonUndoEdits = Object.values( action.meta.undo.edits ).filter( ( edit ) => typeof edit !== 'function' );
+			const comparisonEdits = Object.values( action.edits ).filter( ( edit ) => typeof edit !== 'function' );
+			if ( ! isShallowEqual( comparisonUndoEdits, comparisonEdits ) ) {
+				nextState.push( {
+					kind: action.kind,
+					name: action.name,
+					recordId: action.recordId,
+					edits: action.edits,
+				} );
+			}
 			return nextState;
 	}