fix: diff now handles edge cases

src/diff.spec.ts

@@ -123,6 +123,24 @@ describe("diff", () =>
       }
     );
 
+    it(
+      "Returns [ ..., [ '-', <removed> ], [ '+', <added> ], ... ] for replaced "
+      +"values.",
+      () =>
+      {
+        expect(diff([ 1 ], [ 2 ])).toEqual([ [ "-", 1 ], [ "+", 2 ] ]);
+      }
+    );
+
+    it("Does not forget additions at the end of b.", () =>
+    {
+      expect(diff([ 1 ], [ 2, 3 ])).toEqual([
+        [ "-", 1 ],
+        [ "+", 2 ],
+        [ "+", 3 ]
+      ]);
+    });
+
     it(
       "Returns [ ..., [ '+', <added> ] ] when a is missing a value.",
       () =>

src/diff.ts

@@ -5,6 +5,7 @@ export const diff = (a: any, b: any): any =>
   {
     if (a instanceof Array && b instanceof Array)
     {
+
       const result: any[] = [];
 
       if (a.length === b.length)
@@ -14,6 +15,8 @@ export const diff = (a: any, b: any): any =>
           return undefined;
       }
 
+      let finalIndices = 0;
+
       a.forEach((value, index) =>
       {
         if (b[index] === undefined)
@@ -32,21 +35,31 @@ export const diff = (a: any, b: any): any =>
 
           else
             result.push([ " ", value ]);
+
+          finalIndices++;
         }
 
         else if (value !== b[index] && value === b[index+1])
+        {
           result.push([ "+", b[index] ], [ " ", value ]);
+          finalIndices += 2;
+        }
+
+        else if (value !== b[index] && value !== b[index+1])
+        {
+          result.push([ "-", value ], [ "+", b[index] ]);
+          finalIndices++;
+        }
 
         else
+        {
           result.push([ " ", value ]);
+          finalIndices++;
+        }
+
       });
 
-      if (result.length < a.length)
-      {
-        a.slice(b.length).forEach((value) =>
-          result.push([ "-", value ]));
-      }
-      else if (result.length < b.length)
+      if (finalIndices < b.length)
       {
         b.slice(a.length).forEach((value) =>
           result.push([ "+", value ]));

src/patching.ts

@@ -1,5 +1,5 @@
 import * as Y from "yjs";
-import { diff, } from "json-diff";
+import { diff, } from "./diff";
 import { arrayToYArray, objectToYMap, } from "./mapping";
 import { State, StoreApi, } from "zustand/vanilla";