Nonsense XDMF output of a vector function of a 1d geometry

To parametrize the space dimension for a vector-valued unknown, it is useful to define always a VectorFunctionSpace even in the 1d case, via the identification between Expression("x[0]") and Expression(["x[0]"]). Suppose that u is such a Function, its Numpy array is well defined (1-d array) and gives correct values.

However the XDMF output of such function produces nonsense values in ParaView, as can be seen via the following MWE.

from fenics import *

mesh = UnitIntervalMesh(10)
V = VectorFunctionSpace(mesh, "CG", 1)
u = Function(V)
u.interpolate(Expression(["x[0]"]))

# XDMF output does not produce any error
# Howver in ParaView nonsense values are affected to u 
File("u.xdmf") << u

# PVD output produces an DOLFIN error
# "Don't know how to handle vector function with dimension other than 2 or 3."
File("u.pvd") << u

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