Ignore undefined type metadata when overriding superjson payloads

Addresses #1968

Author: myftija

packages/core/package.json

@@ -188,6 +188,7 @@
     "execa": "^8.0.1",
     "humanize-duration": "^3.27.3",
     "jose": "^5.4.0",
+    "lodash.get": "^4.4.2",
     "nanoid": "3.3.8",
     "prom-client": "^15.1.0",
     "socket.io": "4.7.4",
@@ -206,6 +207,7 @@
     "@epic-web/test-server": "^0.1.0",
     "@trigger.dev/database": "workspace:*",
     "@types/humanize-duration": "^3.27.1",
+    "@types/lodash.get": "^4.4.9",
     "@types/readable-stream": "^4.0.14",
     "ai": "^3.4.33",
     "defu": "^6.1.4",

packages/core/src/v3/utils/ioSerialization.ts

@@ -12,6 +12,7 @@ import { SemanticInternalAttributes } from "../semanticInternalAttributes.js";
 import { TriggerTracer } from "../tracer.js";
 import { zodfetch } from "../zodfetch.js";
 import { flattenAttributes } from "./flattenAttributes.js";
+import get from "lodash.get";
 
 export type IOPacket = {
   data?: string | undefined;
@@ -505,13 +506,46 @@ function safeJsonParse(value: string): any {
   }
 }
 
+/**
+ * Replaces the data in a SuperJSON-serialized string with new payload data while preserving
+ * the original type metadata (Dates, BigInts, Sets, Maps, etc.).
+ *
+ * It is primarily useful for our run replay functionality where we want to preserve the original
+ * type metadata for the new payload.
+ *
+ * Note that `undefined` type metadata is ignored when the corresponding field is overriden in the
+ * new payload, i.e., fields which were previously undefined in the original payload are restored into
+ * the primitive type they have in the new payload, instead of `undefined`.
+ * This is a workaround for https://github.com/triggerdotdev/trigger.dev/issues/1968.
+ *
+ * @param original - A SuperJSON-serialized string containing the original data with type metadata
+ * @param newPayload - A JSON string containing the new data to replace the original payload
+ * @returns The deserialized object with new data but original type metadata preserved
+ *
+ * @throws {Error} If the newPayload is not valid JSON
+ */
 export async function replaceSuperJsonPayload(original: string, newPayload: string) {
   const superjson = await loadSuperJSON();
   const originalObject = superjson.parse(original);
+  const newPayloadObject = JSON.parse(newPayload);
   const { meta } = superjson.serialize(originalObject);
 
+  if (meta?.values) {
+    const originalUndefinedKeys = Object.entries(meta.values)
+      .filter(([, value]) => Array.isArray(value) && value.at(0) === "undefined")
+      .map(([key]) => key);
+
+    const overridenUndefinedKeys = originalUndefinedKeys.filter(
+      (key) => get(newPayloadObject, key) !== undefined
+    );
+
+    overridenUndefinedKeys.forEach((key) => {
+      delete (meta.values as Record<string, any>)[key];
+    });
+  }
+
   const newSuperJson = {
-    json: JSON.parse(newPayload) as any,
+    json: newPayloadObject,
     meta,
   };