Input pull-up doesn't work on expanders

[scottgonzalez]

I'm using an MCP23017, which supports pull-up resistors on all pins. When initializing a button with isPullup: true, the pull-up resistor is not activated on the pin.

[scottgonzalez]

I found a way to get this working. Here's more context and some follow-up questions:

I expected the following code to work:

    const expander = new five.Expander({
      controller: "MCP23017",
      address: 0x21,
    });
    const virtual = new five.Board.Virtual(expander);

    const button = new five.Button({
      board: virtual,
      isPullup: true,
      pin: 5,
    });

However, this only configures the pin to be an input pin, without the internal pull-up resistor enabled. Looking through the code, I saw that the MCP23017 code does have support for controlling the pull-up registers and I was able to get the button to work with the following code:

    const expander = new five.Expander({
      controller: "MCP23017",
      address: 0x21,
    });
    const virtual = new five.Board.Virtual(expander);

    // ADDED COMMAND
    expander.pullUp(5, virtual.io.HIGH)

    const button = new five.Button({
      board: virtual,
      isPullup: true,
      pin: 5,
    });

So I have two questions:

1. Is the expectation that the first block of code should have worked?
2. If the button API alone is not expected to work, is my current approach correct or am I reaching too far into the internals?