containinclude

Containinclude is a term used to describe a content inclusion mechanism that combines the act of including content with a notion of containment. In this model, an included fragment is brought into a host document or template, but its internal scope, styles, and scripts are kept separate from the surrounding content to prevent leakage of variables, CSS, or event handlers. The concept is discussed in templating theory and in some content management workflows as a way to improve modularity and safety when assembling complex layouts.

The core idea is to render an external fragment and insert it into the host while wrapping it in a containment boundary. This boundary can take the form of a scoped namespace, a sandboxed wrapper, or a style-scope mechanism that confines selectors so they do not affect the outer document. Containinclude supports passing a controlled set of parameters from the host to the included fragment.

In practice, containinclude is expressed via a directive or function such as containinclude(source, options). Options may specify containment mode (for example, shadow or scoped), data it should receive, and whether certain assets are isolated or shared. Typical implementations isolate CSS, sandbox scripts, and keep the included fragment’s variables separate from the host’s variable scope.

Benefits include safer reuse of components, reduced risk from third-party fragments, and clearer boundaries between template parts. Drawbacks include added complexity, potential performance overhead, and limited tooling or standards, since containinclude is not part of a formal specification in major templating ecosystems.

As a concept, containinclude remains theoretical in many communities and is often discussed as a design option rather than an existing feature. It intersects with include directives, content projection, and Shadow DOM-like isolation, offering a way to balance modularity with encapsulation.