Years have gone by, and it is still not possible in using the Python Arcpy classes and functions to determine whether a map layer (or layer file) has any joins, still less what datasets are joined.
Nor is there such a method in the ArcPro equivalent to Arcpy.
Thanks for this posting. Wow!, that really is exploring the deep state of arcgis! I fear it isn't quite what I want because the context requires (according to the try..except clause in the code) that it be used within an interactive python window, whereas my need was a non-interactive bookkeeping use. But your example certainly gives me a window into the deep underpinning of esri/com.
Robert Stevens, a pretty easy change to run the way you want. Instead of re-posting code, I updated the code in my earlier post to run outside of an ArcGIS Desktop application. Just remember to set the MXD path at the start of the code.
