feat: add toJson method to Timestamp

[OutdatedGuy]

Related Issues

fixes #289

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[gemini-code-assist]

Code Review

This pull request adds a toJson method to the Timestamp class to make it encodable, along with corresponding unit tests and a changelog update. The reviewer recommends implementing a symmetric fromJson factory constructor, changing the return type of toJson to the idiomatic Map<String, dynamic>, and adding unit tests to verify the deserialization logic.

[codecov-commenter]

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✅ All modified and coverable lines are covered by tests.
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[demolaf]

I think this should be in the firebase_functions package itself, specifically CallableResponse in callable.dart https://github.com/firebase/firebase-functions-dart/blob/main/lib/src/https/callable.dart#L419-L457.

Also, Timestamp.toJson() should not be used internally since the bundle serialization format requires a different set of map keys (seconds/nanos).

[OutdatedGuy]

hi @demolaf, the Timestamp in node.js is natively encodable without depending on firebase-functions

import { Timestamp } from "firebase-admin/firestore";

const now = Timestamp.now();

console.log(JSON.stringify(now)); // {"_seconds":1782405004,"_nanoseconds":354000000}

Having a native toJson method would be better for custom dart backends not using firebase cloud functions.

---

Also, the encode method you linked seems to used only for streaming responses, not for CallableResult.

CallableResult uses dart:convert's jsonEncode method:

https://github.com/firebase/firebase-functions-dart/blob/bf539c4863b2ba90c8d6e0ef166119ce083dca0e/lib/src/https/callable.dart#L45-L49

[demolaf]

@Lyokone @lahirumaramba can I get your thoughts on this?

my main concern here is Timestamp.toJson() if added can be called via jsonEncode which is a risk e.g. BundleMetadata https://github.com/firebase/firebase-admin-dart/blob/main/packages/google_cloud_firestore/lib/src/bundle.dart#L61-L72 uses Timestamp but in the future can be mistaken and Timestamp.toJson() used.

firebase functions node never had this concern because it doesn't declare a Timestamp.toJson().

@OutdatedGuy encode is not only for streaming responses, see node reference https://github.com/firebase/firebase-functions/blob/master/src/common/providers/https.ts#L919-L927 it's job here is to convert types into json compatible values/throws for incompatible json values and that's actually a bug that it is not being called in CallableResult.toResponse().

the idea here is to let firebase functions dart handle functions specific work instead of firebase admin since it can't defend against node's default behavior.