plotting - Combining Mesh and FrameLabel in ArrayPlot fails

I would like to create a labeled ArrayPlot with Mesh->True for example:

ArrayPlot[{{1, 0}, {0, 1}}, FrameLabel -> x, Mesh->True]

This does not show the FrameLabel, but

ArrayPlot[{{1, 0}, {0, 1}}, FrameLabel -> x]

does. I would guess it is a bug, but maybe there is some reason and I can work around it? I am on Mathematica 10.1.0.0 Linux.

Answer

The issue is that ArrayPlot[{{1, 0}, {0, 1}}, FrameLabel -> x, Mesh->True] renders the plot without a frame (hence no framelabel):

ArrayPlot[{{1, 0}, {0, 1}}, FrameLabel -> x, Mesh->True]

What is happening can be seen in a simpler example without FrameLabel:

ArrayPlot[{{1, 0}, {0, 1}}]

Options[ArrayPlot[{{1, 0}, {0, 1}}], Frame]

{Frame -> Automatic}

Somehow adding the option Mesh->True sets the option Frame to False:

 ArrayPlot[{{1, 0}, {0, 1}}, Mesh -> True]

Options[ArrayPlot[{{1, 0}, {0, 1}}, Mesh -> True], Frame]

{Frame -> False}

The fix is to add the option Frame->True:

ArrayPlot[{{1, 0}, {0, 1}}, Frame -> True, FrameLabel -> x, Mesh -> True]