Updated Exists/NotExists for the new architecture.

src/renderer/renderer.rs

@@ -260,6 +260,52 @@ impl<'a> DustRenderer<'a> {
                     }
                 }
             }
+            DustTag::DTExists(container) => {
+                let new_breadcrumbs = self.new_breadcrumbs_partial(
+                    breadcrumbs,
+                    breadcrumbs,
+                    None,
+                    &container.explicit_context,
+                );
+                let val = walk_path(breadcrumbs, &container.path.keys)
+                    .map(|ice| ice.into_context_element(self, breadcrumbs));
+                return match val {
+                    Ok(Some(v)) if v.get_context_element_reference().is_truthy() => self
+                        .render_maybe_body(
+                            &container.contents,
+                            new_breadcrumbs.as_ref().unwrap_or(breadcrumbs),
+                            blocks,
+                        ),
+                    _ => self.render_maybe_body(
+                        &container.else_contents,
+                        new_breadcrumbs.as_ref().unwrap_or(breadcrumbs),
+                        blocks,
+                    ),
+                };
+            }
+            DustTag::DTNotExists(container) => {
+                let new_breadcrumbs = self.new_breadcrumbs_partial(
+                    breadcrumbs,
+                    breadcrumbs,
+                    None,
+                    &container.explicit_context,
+                );
+                let val = walk_path(breadcrumbs, &container.path.keys)
+                    .map(|ice| ice.into_context_element(self, breadcrumbs));
+                return match val {
+                    Ok(Some(v)) if v.get_context_element_reference().is_truthy() => self
+                        .render_maybe_body(
+                            &container.else_contents,
+                            new_breadcrumbs.as_ref().unwrap_or(breadcrumbs),
+                            blocks,
+                        ),
+                    _ => self.render_maybe_body(
+                        &container.contents,
+                        new_breadcrumbs.as_ref().unwrap_or(breadcrumbs),
+                        blocks,
+                    ),
+                };
+            }
             _ => panic!("Unsupported tag"),
         }
         Ok("".to_owned())