[OASIS Issue Tracker] (ODATA-781) substring: what to return if the start index is outside the first argument string, or the desired length exceeds the remaining string length

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    [ https://issues.oasis-open.org/browse/ODATA-781?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=59530#comment-59530 ] 

Ralf Handl commented on ODATA-781:
----------------------------------

Also for JavaScript substring:

If indexA is larger than indexB, then the effect of substring() is as if the two arguments were swapped; for example, str.substring(1, 0) == str.substring(0, 1).

Translating these indexA-indexB rules to our index-length syntax would mean
- negative length means "substring from index backward", negative length reaching before start of string is allowed, all characters before index are returned
- negative index results in length:=length+index, index:=0

With that we would have a defined behavior for all edge cases

> substring: what to return if the start index is outside the first argument string, or the desired length exceeds the remaining string length
> --------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: ODATA-781
>                 URL: https://issues.oasis-open.org/browse/ODATA-781
>             Project: OASIS Open Data Protocol (OData) TC
>          Issue Type: Improvement
>          Components: OData URL Conventions
>    Affects Versions: V4.0_ERRATA02
>         Environment: [Proposed]
>            Reporter: Ralf Handl
>             Fix For: V4.0_ERRATA03
>
>
> This could be a "bad request" returning no results at all, or it could evaluate to null, which may just lead to excluding the offending instance from the result.
> Or a mix of both: negative start index is "bad request", start index or desired length beyond the end of the first argument is "null".



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