`vm.writeJson` should also be able to add new keys

[wottpal]

Component

Forge

Describe the feature you would like

Currently, vm.writeJson is only able to update existing keys which makes it really cumbersome to use when deploying new contracts for the first time and printing them to a file. Instead, it should be able to add new key & value pairs with it, too.

It should also be possible to add nested keys where the parent(s) aren't existing yet as well.

Or at least, the docs should be updated with an easy example on how to add a new (nested) key to an existing JSON file.

From the docs:

This is useful to replace some values in a JSON file without having to first parse and then reserialize it. Note that the JSON path must indicate an existing key, so it’s not possible to add new keys this way.

Additional context

No response

[wottpal]

Would be dope to get this implemented. Is there any blocker I'm not aware of? Or why was it implemented this way in the first place? :)

cc @DaniPopes

[Thegaram]

It looks like foundry uses jsonpath_lib::replace_with to implement this:

foundry/crates/cheatcodes/src/json.rs

Lines 276 to 279 in e01038f

	let value =
	jsonpath_lib::replace_with(data, &canonicalize_json_path(valueKey), &mut |_| {
	Some(json.clone())
	})?;

And the jsonpath library currently does not provide a way to insert a new key.

[sakulstra]

Just stumbled over this one as well - would imo be a quite big ux improvement to be able to write a json key directly.
Perhaps relevant

[deluca-mike]

To be honest, without trying to be too critical, but the json library needs an overhaul, from both an implementation and UX point of view.

For example: https://book.getfoundry.sh/reference/cheatcodes/serialize-json#example

string memory obj1 = "some key";
vm.serializeBool(obj1, "boolean", true);
vm.serializeUint(obj1, "number", uint256(342));
 
string memory obj2 = "some other key";
string memory output = vm.serializeString(obj2, "title", "finally json serialization");
string memory finalJson = vm.serializeString(obj1, "object", output);
 
vm.writeJson(finalJson, "./output/example.json");

results in

{
    "boolean": true,
    "number": 342,
    "object": {
        "title": "finally json serialization"
    }
}

What is obj1 as "some key" and obj2 as "some other key" even doing? The fact that none of the serializeXXX returns are needed except the last one is indicated of some serious side effects and confusing, obfuscated, or undocumented functionality.

You just need functional serializers and deserializers for each type, json key pathing, and a way to read from and write to json keys at a file or in memory. The additional and overloaded non-functional stuff probably makes adding or modifying functionally and documentation a pain.

Anyway, being able to add keys to a json file is very important, and almost makes the overloaded vm.writeJson useless and confusing.