Github user dalaro commented on the issue:
https://github.com/apache/tinkerpop/pull/372
I pulled master (@ fc79de813c788ee141175bbf1ea6d0cdefa94a0f) and confirmed
that the bug still existed. I didn't apply your proposed change right away.
Here a `gremlin.sh` session that shows the buggy behavior. I'm also pushing a
unit test that I developed first, but it's easier to see what's going wrong in
this `gremlin.sh` session than in the source code for a unit test.
```
$ `find gremlin-console/target -name gremlin.sh`
\,,,/
(o o)
-----oOOo-(3)-oOOo-----
plugin activated: tinkerpop.server
plugin activated: tinkerpop.utilities
plugin activated: tinkerpop.tinkergraph
gremlin> sg =
org.apache.tinkerpop.gremlin.structure.util.star.StarGraph.open()
==>stargraph[starOf:null]
gremlin> v = sg.addVertex('name', 'foo')
==>v[0]
gremlin> v.addEdge('self', v)
==>e[2][0-self->0]
gremlin> sg.traversal().V().inE('self')
==>e[2][0-self->0]
gremlin> sg.traversal().V().outE('self')
==>e[2][0-self->0]
gremlin> sg.traversal().V().bothE('self')
==>e[2][0-self->0]
==>e[2][0-self->0]
// NOTE: StarOutEdge in the inEdges datastructure
gremlin> v.inEdges.values().iterator().next().get(0).getClass()
==>class
org.apache.tinkerpop.gremlin.structure.util.star.StarGraph$StarOutEdge
gremlin> filter = new
org.apache.tinkerpop.gremlin.process.computer.GraphFilter()
==>graphfilter[none]
gremlin> filter.setEdgeFilter(__.bothE("self"))
==>null
gremlin> sg.applyGraphFilter(filter)
==>Optional[stargraph[starOf:v[0]]]
// NOTE: no inE results, double outE results after GraphFilter is applied
gremlin> sg.traversal().V().inE('self')
gremlin> sg.traversal().V().outE('self')
==>e[2][0-self->0]
==>e[2][0-self->0]
gremlin> sg.traversal().V().bothE('self')
==>e[2][0-self->0]
==>e[2][0-self->0]
gremlin>
```
There are a couple of things worth noting above:
* the `inEdges` datastructure contains a `StarOutEdge` when we construct
the graph this way
* the final post-filtering `inE` and `outE` are incorrect (an indirect
consequence of the first point)
These steps produce different behavior depending on whether I invoke
`StarGraph.open()` or call `StarGraph.of(<some self-looped tinkervertex>)`. If
I do the latter, I get a `StarInEdge` in the `inEdges` map and a `StarOutEdge`
in the `outEdges` map, and in turn avoid this particular filtering bug.
**Good news**: your change makes sense and fixes the bug I initially
reported (both-filtering).
**Bad news**: I think there are more graph filtering bugs on StarGraph that
can create half-edges
When I filter a self-loop star graph for either in or out, I get stuff like
this (symmetrical for `.inE`):
```
gremlin> filter = new
org.apache.tinkerpop.gremlin.process.computer.GraphFilter()
==>graphfilter[none]
gremlin> filter.setEdgeFilter(__.outE("self"))
==>null
gremlin> sg.applyGraphFilter(filter)
==>Optional[stargraph[starOf:v[0]]]
gremlin> sg.traversal().V()
==>v[0]
gremlin> sg.traversal().V().inE('self')
gremlin> sg.traversal().V().outE('self')
==>e[2][0-self->0]
gremlin> sg.traversal().V().bothE('self')
==>e[2][0-self->0]
gremlin>
```
@okram: This doesn't look correct, but then again, I don't really know what
it should do. Should it completely destroy the self-loop, so that
inE/bothE/outE all fail to emit anything associated with the self-loop? Should
it transform the self-loop into a single-directional edge (which seems like one
interpretation for what it does now, in which case it might be correct)?
I noticed that the name of my original branch is nonsense ("DSP-1397"). I
don't think that can be changed after a PR is created. So, I'm opening a pair
of new PRs: one for tp31 and one for master.
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