[jira] Closed: (TAPESTRY-1928) Coercion from null to Boolean yields false instead of null

["Howard M. Lewis Ship (JIRA)" <de...@tapestry.apache.org>]

     [ https://issues.apache.org/jira/browse/TAPESTRY-1928?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Howard M. Lewis Ship closed TAPESTRY-1928.
------------------------------------------

    Resolution: Invalid
      Assignee: Howard M. Lewis Ship

Again, this is desired, expected behavior.  And, again, I think we need to revisit null handling to control more explicitly how nulls are treated when rendering and when submitting.

> Coercion from null to Boolean yields false instead of null
> ----------------------------------------------------------
>
>                 Key: TAPESTRY-1928
>                 URL: https://issues.apache.org/jira/browse/TAPESTRY-1928
>             Project: Tapestry
>          Issue Type: Bug
>          Components: tapestry-ioc
>    Affects Versions: 5.0.6
>            Reporter: Geoff Callender
>            Assignee: Howard M. Lewis Ship
>
> Boolean has 3 states: null, true, false, but the coercer coerces null to false.  While this is correct behaviour for the boolean primitive (which has only 2 states), it is not correct for Boolean.
> The same argument applies here as in TAPESTRY-1648 which dealt with null BigDecimal and Integer.
> A practical consequence is that a BooleanValueEncoder that is 3-value aware becomes useless because the coercer will override it.  
> For example I combined a BooleanValueEncoder with Select to allow a user to choose between "", "true", and "false".  But when the user chooses "", they unexpectedly get the same result as choosing "false".  Here's the template code:
>    <select t:id="active" t:type="Select" value="active" model="actives" encoder="booleanValueEncoder"/>
> Here's the relevant java:
>    static private final Boolean[] ACTIVES = { null, Boolean.TRUE, Boolean.FALSE };
>    static private final BooleanValueEncoder BOOLEAN_VALUE_ENCODER = new BooleanValueEncoder();
>    public Boolean getActive() {
>       return _active;
>    }
>    public  void setActive(Boolean active) {
>       _active = active;
>    }
>    public Boolean[] getActives() {
>       return ACTIVES;
>    }
> 	
>    public BooleanValueEncoder getBooleanValueEncoder() {
>       return BOOLEAN_VALUE_ENCODER;
>    }
> Here's a BooleanValueEncoder:
>    public class BooleanValueEncoder implements ValueEncoder<Boolean> {
>       public String toClient(Boolean value) {
>          return value == null ? "" : value.toString();
>       }
>       public Boolean toValue(String clientValue) {
>          return clientValue.equals("") ? null : Boolean.valueOf(clientValue);
>       }
>    }
> When the user chooses "", Tapestry calls setActive(Boolean.FALSE) instead of setActive(null).

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