Need a mechanism to set user javadoc path

--------------------USER REPORT -------------

FULL PRODUCT VERSION :
java version "9"
Java(TM) SE Runtime Environment (build 9+178)
Java HotSpot(TM) 64-Bit Server VM (build 9+178, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.10586]

A DESCRIPTION OF THE PROBLEM :
I have a jar, gson.jar, and its accompanying javadoc jar, gson-javadoc.jar, as built by maven, which I believe uses the Java API Documentation Generator.

If I run jshell --class-path gson.jar;gson-javadoc.jar and then try and view the documentation, none is found.

jshell> com.google.gson.Gson <tab> <tab>

com.google.gson.Gson
<no documentation found>

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
jshell --class-path gson.jar;gson-javadoc.jar

jshell> com.google.gson.Gson <tab> <tab>



EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The class-use documentation is displayed. By association, any javadoc loaded on the classpath can be accessed.
ACTUAL -
com.google.gson.Gson
<no documentation found>

REPRODUCIBILITY :
This bug can be reproduced always.