meson/docs/markdown/snippets/has_external_property.md

Check if native or cross-file properties exist

It is now possible to check whether a native property or a cross-file property exists with meson.has_external_property('foo'). This is useful if the property in question is a boolean and one wants to distinguish between "set" and "not provided" which can't be done the usual way by passing a fallback parameter to meson.get_external_property() in this particular case.