source

The source function returns the content of a template without rendering it:

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{{ source('template.html.twig') }}
{{ source(some_var) }}

When you set the ignore_missing flag, Twig will return an empty string if the template does not exist:

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{{ source('template.html.twig', ignore_missing = true) }}

The function uses the same template loaders as the ones used to include templates. So, if you are using the filesystem loader, the templates are looked for in the paths defined by it.