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https://issues.apache.org/jira/browse/FREEMARKER-110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16705736#comment-16705736
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Daniel Dekany commented on FREEMARKER-110:
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You can't query if the invocation has specified a nested content or not, by
design. That has the same reason why in XML {{<foo></foo>}} and {{<foo/>}} are
indistinguishable when you process XML. It would be less a problematic design
decision to be able to query if the nested content is 0 length, but it leads to
edge cases that the users of such a macro (a macro that cares about whether the
nested content is empty) will be confused about, such as when the body is not
empty but: (a) contains only whitespace; (b) contains only comments (and
whitespace); (c) contains other directive calls that do not produce output on
runtime. Therefore, if you really, really need to do such a check, then it's
better be a case where the question is really if the output produced by the
nested content is discardable. In such case, you should capture the nested
output like {{<#local nestedOutput><#nested></#local>}}, then check if
{{nestedOutput}} is empty (after trimming), then print it with
{{$\{nestedOutput}}}. (Be careful with auto-escaping, if you use that.)
> describe how to test whether "nested" in a macro is empty or not
> ----------------------------------------------------------------
>
> Key: FREEMARKER-110
> URL: https://issues.apache.org/jira/browse/FREEMARKER-110
> Project: Apache Freemarker
> Issue Type: Improvement
> Reporter: Ralf Hauser
> Priority: Major
>
> [https://freemarker.apache.org/docs/ref_directive_macro.html#autoid_106]
>
> Then, I could put something else, if I know that no nested content is coming
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