Support using rooted macro with vectors.

[jdm]

We created our RootedVec type back before we supported storing arbitrary traceable types in SpiderMonkey's Rooted class. Now that we can do that, we can replicate SpiderMonkey's RootedVec, which is just a Rooted wrapper around a vector.

Testing: New unit test added.
Servo PR: servo/servo#41921

[jdm]

Ack, there was a new sccache release but it doesn't include x86_64 binaries for macOS, only arm64, so our x86_64 macOS build is busted.

[sagudev]

I think it would make more sense to impl RootedGuard<'_, Vec<JSVal>> as that's how we do other stuff.

[jdm]

Can you give an example of what you mean? There's a matching impl for RootedVec right above this one.

[jdm]

Similarly,

mozjs/mozjs-sys/src/jsimpls.rs

Lines 142 to 167 in 369880c

	impl<const N: usize> From<&Rooted<ValueArray<N>>> for JS::HandleValueArray {
	fn from(array: &Rooted<ValueArray<N>>) -> JS::HandleValueArray {
	JS::HandleValueArray {
	length_: N,
	elements_: array.data.get_ptr(),
	}
	}
	}
	impl From<&JS::CallArgs> for JS::HandleValueArray {
	fn from(args: &JS::CallArgs) -> JS::HandleValueArray {
	JS::HandleValueArray {
	length_: args.argc_ as usize,
	elements_: args.argv_ as *const _,
	}
	}
	}
	impl From<JS::Handle<JSVal>> for JS::HandleValueArray {
	fn from(handle: JS::Handle<JSVal>) -> JS::HandleValueArray {
	JS::HandleValueArray {
	length_: 1,
	elements_: handle.ptr,
	}
	}
	}

[sagudev]

Above is impl for RootedVec, but RootedGuard usually have handle() and handle_mut() methods so here it would be smth like:

impl<'a,> RootedGuard<'a, Vec<JSVal>>
{
fn handle_value_array(&self) -> JS::HandleValueArray {
        JS::HandleValueArray {
            length_: self.len(),
            elements_: self.deref().as_ptr(),
        }
    }
}

[sagudev]

Hm, given that HandleValueArray has no lifetime associated it can outlive the root so it should be unsafe (thus all from conversions are unsound).

[jdm]

For the purposes of this PR, I'd rather match the existing HandleValueArray creation code that I linked in https://github.com/servo/mozjs/pull/697/changes/BASE..60cd1d696448318e06ec28f103b30641c9c8ffa6#r2700733569. If we want to change that, I think we should change all of them together.

[sagudev]

fair

[sagudev]

Ack, there was a new sccache release but it doesn't include x86_64 binaries for macOS, only arm64, so our x86_64 macOS build is busted.

We can wait for mozilla/sccache#2554 or temporarily disable sccache on x86_64 macOS.

[Taym95]

I think this is what I was trying to do here https://github.com/servo/mozjs/pull/630/changes#diff-737e12000758c48503126ab75c14db2c9d0854a95487ebdd0a51d99f991822efR289 but I ended up creating a whole new struct DynamicValueArray and struct FixedValueArray.