Added "should handle checkpoints correctly" Unit Tests + Fix 2 Bugs That Were Preventing Them From Passing

langgraph/src/channels/base.ts

@@ -88,17 +88,15 @@ export async function createCheckpoint<Value>(
     channelVersions: { ...checkpoint.channelVersions },
     versionsSeen: { ...checkpoint.versionsSeen },
   };
-  for (const k in channels) {
-    if (newCheckpoint.channelValues[k] === undefined) {
-      try {
-        newCheckpoint.channelValues[k] = await channels[k].checkpoint();
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-      } catch (error: any) {
-        if ("name" in error && error.name === EmptyChannelError.name) {
-          // no-op
-        } else {
-          throw error; // Rethrow unexpected errors
-        }
+  for (const k of Object.keys(channels)) {
+    try {
+      newCheckpoint.channelValues[k] = await channels[k].checkpoint();
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    } catch (error: any) {
+      if (error.name === EmptyChannelError.name) {
+        // no-op
+      } else {
+        throw error; // Rethrow unexpected errors
       }
     }
   }

langgraph/src/channels/binop.ts

@@ -29,11 +29,14 @@ export class BinaryOperatorAggregate<Value> extends BaseChannel<
     this.value = initialValueFactory?.();
   }
 
-  public empty(_?: Value): BinaryOperatorAggregate<Value> {
+  public empty(checkpoint?: Value): BinaryOperatorAggregate<Value> {
     const empty = new BinaryOperatorAggregate(
       this.operator,
       this.initialValueFactory
     );
+    if (checkpoint) {
+      empty.value = checkpoint;
+    }
     return empty;
   }
 
@@ -61,7 +64,7 @@ export class BinaryOperatorAggregate<Value> extends BaseChannel<
   }
 
   public checkpoint(): Value {
-    if (!this.value) {
+    if (this.value === undefined) {
       throw new EmptyChannelError();
     }
     return this.value;

langgraph/src/tests/pregel.test.ts

@@ -386,7 +386,7 @@ it("should process two inputs to two outputs validly", async () => {
   expect(await app.invoke(2)).toEqual([3, 3]);
 });
 
-it.skip("should handle checkpoints correctly", async () => {
+it("should handle checkpoints correctly", async () => {
   const addOne = jest.fn(
     (x: { total: number; input: number }): number => x.total + x.input
   );