[Bf-cycles] sample with lamp changes light paths- normal behavior?

[Bassam Kurdali]

Hey folks, I've constructed an artificial example here to illustrate the
issue.
I've got a plane (named selective) that has transparent shader and a mix
node with Light Path 'Is Shadow Ray' as input to factor. The idea is
that the shadows would be colored one color, but e.g. diffuse and glossy
reflections with another.

This is being lit with a mesh cube and an emission shader.

If 'Sample as lamp' is on on the Cube emission shader, the result is a
yellow transparent plane, with a blue shadow.

If 'Sample as lamp' is off on the Cube emission shader, the result is a
yellow transparent plane, with a yellow shadow.

Is this quirk a normal result? I realize that transparent shader is
somehow 'fake' - or is it a bug?

blend file http://urchn.org/misc/test.blend
image1 http://urchn.org/misc/sample_aslamp.png
image2 http://urchn.org/misc/nosampleaslamp.png

cheers
Bassam