[jira] [Updated] (TINKERPOP-800) Domain/Range checking during traversal construction.

["Stephen Mallette (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TINKERPOP-800?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Stephen Mallette updated TINKERPOP-800:
---------------------------------------
    Summary: Domain/Range checking during traversal construction.  (was: [Proposal] Domain/Range checking during traversal construction.)

> Domain/Range checking during traversal construction.
> ----------------------------------------------------
>
>                 Key: TINKERPOP-800
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-800
>             Project: TinkerPop
>          Issue Type: Improvement
>          Components: process
>    Affects Versions: 3.0.2-incubating
>            Reporter: Marko A. Rodriguez
>            Priority: Major
>              Labels: breaking
>
> I think we should add two new methods to {{Step}}.
> {code}
> Step.getDomain() -> Class
> Step.getRange() -> Class
> {code}
> Now, when someone does:
> {code}
> g.V().out()
> {code}
> {{GraphStep}} will report that its range is {{Vertex.class}}. {{VertexStep}} will report its domain to be {{Vertex.class}}. Good. No typing issues. However, when you do this:
> {code}
> g.E().out()
> {code}
> {{GraphStep}} will report that its range is {{Edge.class}}. {{VertexStep}} will report its domain to be {{Vertex.class}} --- {{IllegalArgumentException: "The provided traversal has an illegal function composition."}}.
> Why is this good -- much better than getting random {{ClassCastExceptions}} at execution time.



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