I have recently encountered some references for books or chapters that do not have publisher fields. However, when using AMA style, the citation still includes the semicolon that would usually come after the publisher field:
To me, this appears incorrect. Is this the intended behavior?
Yes, it’s intended, in the sense it’s what the style dictates. See here.
But it’s really a bug in the style, as the publisher should be placed in a group; probably the one just following it. E.g. I think we want it changed to something like this (the punctuation would still need fixing though; I just threw this together quickly, though you can experiment yourself if you like):
<group suffix="." prefix="; ">
<text macro="publisher" prefix=" "/>
<text variable="page" prefix=":"/>
Or since the publisher macro is called in a couple of places, it might benefit from some more invasive changes, like a new “published” macro.