I am using grunt-assemble, in grunt task I add custom option of language by following below documentation
assemble docs and below is the image of my grunt task grunt task
{{language}}
{{#withSort pages "data.navSortOrder"}}
{{langugae}}
{{#is data.showInNav true}}
<li{{#is ../../page.dest this.dest}} class="active"{{/is}}>
{{language}}
{{/is}}
{{/withSort}}
In above code language outside the withsort block is outputting the expected result but in withsort block language option isn't outputting anything