From c79bbcb082e21ef60ce867e8d5c05a49c433c766 Mon Sep 17 00:00:00 2001
From: Riad Benguella <benguella@gmail.com>
Date: Mon, 27 Nov 2017 14:59:09 +0100
Subject: [PATCH] Block versioning: Introduce a migration function

---
 blocks/api/parser.js      | 14 ++++++++++----
 blocks/api/test/parser.js |  3 ++-
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/blocks/api/parser.js b/blocks/api/parser.js
index 82add30a463e8f..ca78755a4b391f 100644
--- a/blocks/api/parser.js
+++ b/blocks/api/parser.js
@@ -147,10 +147,16 @@ export function getAttributesFromDeprecatedVersion( blockType, innerHTML, attrib
 			...omit( blockType, [ 'attributes', 'save', 'supports' ] ), // Parsing/Serialization properties
 			...blockType.deprecated[ i ],
 		};
-		const deprecatedBlockAttributes = getBlockAttributes( deprecatedBlockType, innerHTML, attributes );
-		const isValid = isValidBlock( innerHTML, deprecatedBlockType, deprecatedBlockAttributes );
-		if ( isValid ) {
-			return deprecatedBlockAttributes;
+
+		try {
+			const deprecatedBlockAttributes = getBlockAttributes( deprecatedBlockType, innerHTML, attributes );
+			const migratedBlockAttributes = deprecatedBlockType.migrate ? deprecatedBlockType.migrate( deprecatedBlockAttributes ) : deprecatedBlockAttributes;
+			const isValid = isValidBlock( innerHTML, deprecatedBlockType, deprecatedBlockAttributes );
+			if ( isValid ) {
+				return migratedBlockAttributes;
+			}
+		} catch ( error ) {
+			// ignore error, it means this deprecated version is invalid
 		}
 	}
 }
diff --git a/blocks/api/test/parser.js b/blocks/api/test/parser.js
index fc850a08730a86..7a8fd86ed929e6 100644
--- a/blocks/api/test/parser.js
+++ b/blocks/api/test/parser.js
@@ -304,6 +304,7 @@ describe( 'block parser', () => {
 							},
 						},
 						save: ( { attributes } ) => <span>{ attributes.fruit }</span>,
+						migrate: ( attributes ) => ( { fruit: 'Big ' + attributes.fruit } ),
 					},
 				],
 			} );
@@ -314,7 +315,7 @@ describe( 'block parser', () => {
 				{ fruit: 'Bananas' }
 			);
 			expect( block.name ).toEqual( 'core/test-block' );
-			expect( block.attributes ).toEqual( { fruit: 'Bananas' } );
+			expect( block.attributes ).toEqual( { fruit: 'Big Bananas' } );
 			expect( block.isValid ).toBe( true );
 			expectFailingBlockValidation();
 		} );