The Power of Traits in Vcs

The Vcs library leverages the provider-based parametric model to offer a flexible and adaptable interface for Git operations. This model, also used in the Eio library (Eio.Resource), allows us to define small scopes of functionality, or Traits, within the Vcs library.

Experience with providers

Our use of the provider based parametric library in Vcs serves as a practical, real-world case study of this pattern.

We aim to bring this pattern to the attention of the community, fostering a general understanding that can be applied to other projects using the same pattern. In essence, understanding the parametrized model of Vcs equates to understanding Eio.Resource, and vice versa.

Granularity of the Interface via Trait Granularity

The Trait design of provider allows us to define specific and isolated sub-functionalities within the Vcs library. This granularity enables different providers to choose which Trait they wish to implement, offering a level of flexibility not possible with a monolithic functor.

With Traits, you can select a provider with the specific set of traits you need, without changing any other code. As explained here, provider interfaces come with some notion of phantom types, offering additional compiler assistance.

In summary, the use of Traits in Vcs provides a flexible, adaptable, and granular interface for Git operations, promoting a broader understanding and application of the provider-based parametric model.