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https://issues.apache.org/jira/browse/SLING-6967?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16055389#comment-16055389
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Konrad Windszus commented on SLING-6967:
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An example would be to include a resource on a fix level (e.g. a logo component
which is being maintained at {{/content/home/jcr:content/logo}})
The HTL of the container script which includes the logo might look like this
{code}
<sly data-sly-use.header="my.own.Header"></sly>
<div data-sly-test="${header.homePageLogoPath}"
data-sly-resource="${header.homePageLogoPath}"></div>
{code}
If the {{data-sly-test}} would not be included, in case the
{{my.own.Header#getHomePageLogoPath()}} would throw an exception, the
data-sly-resource would still be executed, because the exception is being
swallowed by the HTL EL and converted to the empty string! That might in the
worst case lead to a cycle because the include is on the same resource again.
With the {{data-sly-test}} the div would not be rendered in case
{{my.own.Header#getHomePageLogoPath()}} would return the empty string or throw
an exception. In my case I would be interested to explicitly throw an
exception, because the rendering of the page does not make sense in case this
use-case occurs (i.e. a logo is not maintained). I cannot easily achieve that
behaviour because I cannot explicitly throw an exception from within the HTL
script (and therefore trigger a generic exception handler in a component
servlet filter).
> Allow to throw exceptions in data-sly-resource for invalid paths
> ----------------------------------------------------------------
>
> Key: SLING-6967
> URL: https://issues.apache.org/jira/browse/SLING-6967
> Project: Sling
> Issue Type: Improvement
> Components: Scripting
> Affects Versions: Scripting HTL Engine 1.0.34
> Reporter: Konrad Windszus
>
> If the path for {{data-sly-resource}} is dynamic you need to set it via
> expression language. If the underlying Java Pojo throws an exception while
> retrieving the path this exception is being caught by HTL EL and leads to the
> empty path (i.e. the behaviour is changed drastically because the wrong
> resource is being included)
> Since propagating the exception through the HTL EL is probably an
> incompatible change I would suggest to add an additional optional option like
> {{isInvalidPath}}. If that is set to {{true}} there should be a
> {{SightlyException}} thrown with an according error message that the given
> path is invalid.
> A concrete use case for that is a reference component, which would otherwise
> end up in a cycle because it would otherwise include itself.
> The only other workaround would be to use {{data-sly-test}} on the
> dynamically retrieved path, but it would not be possible to throw an
> exception here (and therefore break rendering of the whole HTL script).
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