Returning nested arrays from host object

[jaredkrinke]

Does anyone have a working (C++) example of returning nested arrays from a host object?

The docs (side note: only the .NET docs have any details; the Win32 version is basically just a function prototype) say:

Nested arrays are supported up to a depth of 3

But I've tried a few different approaches and can't get it to work. I'm returning (via an out param) a VARIANT, and I've tried:

1. A SAFEARRAY of VT_VARIANT containing SAFEARRAYs of VT_VARIANTs (this results in nested arrays, but the "leaf" values are all null, e.g. [[null, null], [null, null]])
2. A SAFEARRAY of VT_VARIANT containing SAFEARRAYs of VT_I4 (this has the same result as the previous one)
3. A SAFEARRAY of rank 2 of VT_VARIANT (this one just returns null)
4. (For the record, I did confirm that a non-nested SAFEARRAY of VARIANT works as expected)

It's odd that I can get the nested arrays to work, but then even trivial values (e.g. VT_I4) end up as null on the JavaScript side.

I can work around this by constructing a big JSON blob, but I'd like to avoid string manipulation/escaping as much as possible.

Edit: I should add that I verified in the Visual Studio C++ debugger that I'm returning a SAFEARRAY of SAFEARRAY, and that the innermost items are set correctly (e.g. vt = VT_I4 and lVal = 123). The issue I'm having is related to how the data is marshaled back to the JavaScript side.

[jaredkrinke]

Interestingly, option 1 above is how nested arrays are marshalled into my C++ code, but they don't get marshalled back out correctly. Seems like either I misinterpreted the docs or there's a bug.

Here's my function:

HRESULT Test([in] VARIANT vin, [out, retval] VARIANT* vout);

And implementation is basically just VariantCopy:

STDMETHODIMP Steam::Test(VARIANT vin, VARIANT* vout) {
    VariantInit(vout);
    VariantCopy(vout, &vin);
    return S_OK;
}

From JavaScript, if I call the function on my host object:

chrome.webview.hostObjects.sync.h.Test([[1, "two"], ["three", 4]])

The result is:

[[null, null], [null, null]]