Server side helper functions for DRY component consumptions

[ttbarnes]

Context

I've worked on many GOV services and noticed that some core pieces of logic required to consume some GOV components are duplicated throughout the services.

For example, to generate a validation error(s) and pass an array to the Error summary component, the same pieces of logic are required in individual services.

These pieces of logic basically consume a field ID and error message and are then mapped into a data structure required for a GOV component.

I imagine a large majority of services built with NodeJS must have similar pieces of logic.

Alternatives

It would be great to have DRY, generic helper functions in govuk-frontend to generate such data structures.

This would improve multiple services and developer experiences by:

• Avoiding repitition.
• Ensuring consistency.
• Reducing lines of code in a service.
• Reducing development time.

For example, there could be the following functions:

• generateValidationError - generate a data structure for a single validation error (E.g, for a form that has 1 form input).
• generateValidationErrors - generate a data structure for multiple validation errors (E.g, for a form with multiple inputs).

After calling these functions, the resulting data can then be easily passed to various GOV components to render validation errors.

With a "helpers" pattern in place, other helpers could also be added, for example to generate summary lists and task statuses, without individual services having to write their own logic. I want to propose a simple example first.

Is there appetite for such helper functions?

Additional information (if applicable)

I've created a proof of concept in my forked repo.

This demonstrates an example for a generateValidationError helper function and in the PR description, how this could be consumed in a service.

Very interested to hear any thoughts on this. Would love to pursue and create a real PR.

If there is appetite for this, perhaps some new pattern pages could be created, for example to demonstrate how to generate validation with such helper functions.

A good example of how this would help a service is for a UKEF - Export Insurance Policies, where we currently have 98 imports for a generateValidationErrors function.