Hi,
                                  
                                  
                                  
                                  I have a repeatable failure with
                                    Photon / m2e / wtp projects. I'm not
                                    sure it is related with m2e, but as
                                    I think it is highly related with
                                    the way project's build path is
                                    configured, your insight may be
                                    important. Also I found no report
                                    about this issue, so I think it is
                                    not an issue for vanilla Eclipse
                                    project.
                                  
                                  
                                  
                                  TLDR; Inspect and Debug shell is
                                    impossible in dependencies in a WTP
                                    Tomcat Server with Photon (Unable to
                                    evaluate the selected _expression_).
                                    It used to work with Oxygen. I find
                                    a workaround, but this bug is really
                                    annoying. Only Debug Server is buggy
                                    ; a Debug as... Junit test works
                                    fine.
                                  
                                  
                                  
                                  This bug can be reproduced
                                    following this steps :
                                  
                                  * download jee package for
                                    eclipse photon (buildid
                                    20180619-1200, eclipse m2e
                                    1.9.0.20180606-2036, eclipse m2e wtp
                                    1.4.0.20180606-2005)
                                  
                                  
                                  * with Git Perspective, add the
                                    git repository and import the
                                    selected project. Maven nature is
                                    detected automatically
                                  
                                  * create a Tomcat 9.0 Server and
                                    add the test webapp
                                  
                                  * Debug Tomcat server
                                  
                                  * put a breakpoint on
                                    TestServlet.doGet
                                  
                                  
                                  * step in
                                    StringUtils.isAllBlank(...)
                                  
                                  * perform an inspect or
                                    debug-shell on
                                    "ArrayUtils.isEmpty(css)"
                                  
                                  * it fails with "Unable to
                                    evaluate the selected _expression_"
                                  
                                  
                                  
                                  A known workaround for this is :
                                  
                                  * click on the stacktrace in
                                    debug view
                                  
                                  * right-click -> Edit source
                                    lookup
                                  
                                  * tick Search for duplicate
                                    source -> apply
                                  
                                  * choose StringUtils.class in the
                                    list (opposed to
                                    org/apache/commons/...)
                                  
                                  * inspect/debug-shell is working
                                    again ; but this process must be
                                    done for all class you want to debug
                                  
                                  
                                  
                                  Do you reproduce this issue ? Do
                                    you think it is m2e related (the way
                                    maven project is configured) or wtp
                                    related ? How can I help to fix this
                                    issue ?
                                  
                                  
                                  
                                  Thanks,
                                  
                                  
                                  
                                  Laurent Almeras