[jira] [Created] (TINKERPOP-2314) Employ by(String) for Map when possible and improve errors around incorrect types

[Stephen Mallette (Jira)]

Stephen Mallette created TINKERPOP-2314:
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             Summary: Employ by(String) for Map when possible and improve 
errors around incorrect types
                 Key: TINKERPOP-2314
                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2314
             Project: TinkerPop
          Issue Type: Improvement
          Components: process
    Affects Versions: 3.3.9
            Reporter: Stephen Mallette
            Assignee: Stephen Mallette


This bit of Gremlin demonstrates both problems for uses of {{by(String)}}:

{code}
gremlin> g.V().values('age').project('x').by('name')
java.lang.Integer cannot be cast to 
org.apache.tinkerpop.gremlin.structure.Element
Type ':help' or ':h' for help.
Display stack trace? [yN]n
{code}

First, users typically expect this to work because they figure they are just 
grabbing a keys value from a {{Map}} and then get the difficult to understand 
message which doesn't tell you how to resolve. As a side note, the way to 
resolve is with:

{code}
gremlin> g.V().valueMap().project('x').by(select('name'))
==>[x:[marko]]
==>[x:[stephen]]
==>[x:[matthias]]
==>[x:[daniel]]
==>[x:[gremlin]]
==>[x:[tinkergraph]]
{code}



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