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