Support serializing/deserializing empty arrays

apps/webapp/app/utils/taskEvent.ts

@@ -5,6 +5,7 @@ import {
   isExceptionSpanEvent,
   millisecondsToNanoseconds,
   NULL_SENTINEL,
+  EMPTY_ARRAY_SENTINEL,
   SemanticInternalAttributes,
   SpanEvent,
   SpanEvents,
@@ -446,6 +447,10 @@ export function rehydrateJson(json: Prisma.JsonValue): any {
     return null;
   }
 
+  if (json === EMPTY_ARRAY_SENTINEL) {
+    return [];
+  }
+
   if (typeof json === "string") {
     return json;
   }

apps/webapp/app/v3/eventRepository.server.ts

@@ -5,6 +5,7 @@ import {
   ExceptionEventProperties,
   ExceptionSpanEvent,
   NULL_SENTINEL,
+  EMPTY_ARRAY_SENTINEL,
   PRIMARY_VARIANT,
   SemanticInternalAttributes,
   SpanEvent,
@@ -1593,6 +1594,10 @@ function rehydrateJson(json: Prisma.JsonValue): any {
     return null;
   }
 
+  if (json === EMPTY_ARRAY_SENTINEL) {
+    return [];
+  }
+
   if (typeof json === "string") {
     return json;
   }

packages/core/src/v3/index.ts

@@ -44,6 +44,7 @@ export {
   primitiveValueOrflattenedAttributes,
   unflattenAttributes,
   NULL_SENTINEL,
+  EMPTY_ARRAY_SENTINEL,
 } from "./utils/flattenAttributes.js";
 export { omit } from "./utils/omit.js";
 export {

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

@@ -1,6 +1,8 @@
 import { Attributes } from "@opentelemetry/api";
+import { debug } from "node:util";
 
 export const NULL_SENTINEL = "$@null((";
+export const EMPTY_ARRAY_SENTINEL = "$@empty_array((";
 export const CIRCULAR_REFERENCE_SENTINEL = "$@circular((";
 
 export function flattenAttributes(
@@ -20,6 +22,11 @@ export function flattenAttributes(
     return result;
   }
 
+  if (Array.isArray(obj) && obj.length === 0) {
+    result[prefix || ""] = EMPTY_ARRAY_SENTINEL;
+    return result;
+  }
+
   if (typeof obj === "string") {
     result[prefix || ""] = obj;
     return result;
@@ -66,6 +73,10 @@ export function flattenAttributes(
           }
         }
       }
+
+      if (!value.length) {
+        result[newPrefix] = EMPTY_ARRAY_SENTINEL;
+      }
     } else if (isRecord(value)) {
       // update null check here
       Object.assign(result, flattenAttributes(value, newPrefix, seen));
@@ -98,7 +109,7 @@ export function unflattenAttributes(
     Object.keys(obj).length === 1 &&
     Object.keys(obj)[0] === ""
   ) {
-    return rehydrateNull(obj[""]) as any;
+    return rehydrateEmptyValues(obj[""]) as any;
   }
 
   if (Object.keys(obj).length === 0) {
@@ -150,7 +161,7 @@ export function unflattenAttributes(
     const lastPart = parts[parts.length - 1];
 
     if (lastPart !== undefined) {
-      current[lastPart] = rehydrateNull(rehydrateCircular(value));
+      current[lastPart] = rehydrateEmptyValues(rehydrateCircular(value));
     }
   }
 
@@ -201,10 +212,14 @@ export function primitiveValueOrflattenedAttributes(
   return attributes;
 }
 
-function rehydrateNull(value: any): any {
+function rehydrateEmptyValues(value: any): any {
   if (value === NULL_SENTINEL) {
     return null;
   }
 
+  if (value === EMPTY_ARRAY_SENTINEL) {
+    return [];
+  }
+
   return value;
 }

packages/core/test/flattenAttributes.test.ts

@@ -61,6 +61,22 @@ describe("flattenAttributes", () => {
     expect(unflattenAttributes(result)).toEqual(input);
   });
 
+  it("flattens empty array attributes correctly", () => {
+    const input: number[] = [];
+
+    const result = flattenAttributes(input);
+    expect(result).toEqual({ "": "$@empty_array((" });
+    expect(unflattenAttributes(result)).toEqual(input);
+  });
+
+  it("flattens empty array child attributes correctly", () => {
+    const input: number[] = [];
+
+    const result = flattenAttributes({ input });
+    expect(result).toEqual({ input: "$@empty_array((" });
+    expect(unflattenAttributes(result)).toEqual({ input });
+  });
+
   it("flattens complex objects correctly", () => {
     const obj = {
       level1: {
@@ -157,13 +173,13 @@ describe("flattenAttributes", () => {
     expect(flattenAttributes(obj, "retry.byStatus")).toEqual(expected);
   });
 
-   it("handles circular references correctly", () => {
+  it("handles circular references correctly", () => {
     const user = { name: "Alice" };
     user["blogPosts"] = [{ title: "Post 1", author: user }]; // Circular reference
 
     const result = flattenAttributes(user);
     expect(result).toEqual({
-      "name": "Alice",
+      name: "Alice",
       "blogPosts.[0].title": "Post 1",
       "blogPosts.[0].author": "$@circular((",
     });
@@ -175,7 +191,7 @@ describe("flattenAttributes", () => {
 
     const result = flattenAttributes(user);
     expect(result).toEqual({
-      "name": "Bob",
+      name: "Bob",
       "friends.[0]": "$@circular((",
     });
   });
@@ -246,10 +262,24 @@ describe("unflattenAttributes", () => {
     };
     expect(unflattenAttributes(flattened)).toEqual(expected);
   });
-
+
+  it("correctly reconstructs empty arrays", () => {
+    const flattened = {
+      "": "$@empty_array((",
+      array1: "$@empty_array((",
+      "array2.[0]": "$@empty_array((",
+    };
+    const expected = {
+      "": [],
+      array1: [],
+      array2: [[]],
+    };
+    expect(unflattenAttributes(flattened)).toEqual(expected);
+  });
+
   it("rehydrates circular references correctly", () => {
     const flattened = {
-      "name": "Alice",
+      name: "Alice",
       "blogPosts.[0].title": "Post 1",
       "blogPosts.[0].author": "$@circular((",
     };