[jira] [Commented] (CONFIGURATION-831) Unresolved (non-existend) environment variables should return null

[Gary D. Gregory (Jira)]

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https://issues.apache.org/jira/browse/CONFIGURATION-831?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17941666#comment-17941666
 ] 

Gary D. Gregory commented on CONFIGURATION-831:
-----------------------------------------------

Sure. As a user I expect you have a good perspective as how to improve the 
documentation 😀

> Unresolved (non-existend) environment variables should return null
> ------------------------------------------------------------------
>
>                 Key: CONFIGURATION-831
>                 URL: https://issues.apache.org/jira/browse/CONFIGURATION-831
>             Project: Commons Configuration
>          Issue Type: New Feature
>          Components: Interpolation
>    Affects Versions: 2.9.0
>            Reporter: Wojtek
>            Priority: Minor
>
> Currently Interpolation of environment variables 
> (https://commons.apache.org/proper/commons-configuration/userguide/howto_basicfeatures.html#Variable_Interpolation)
>  return un-interpolated string if the environment variable doesn't exists at 
> all.
> It would be very convenient and (I feel) more consistent if, in that case, 
> 'null' would be returned.
>  
> Alternatively, option to specify default if the variable doesn't exist would 
> also work.
> I.e. something along the lines:
> ```
> ${env:JAVA_HOME:<default value>}
> ```
>  
> From my experiments, even if we try to register custom interpolator it's not 
> possible to explicitly return `null` from it.



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