Convert `[]error` to use multi errors available in 1.20

[thrawn01]

Thanks for the wonderful library! After converting from a different library, I have a single suggestion!

The current code base returns multiple errors which is inconvenient to use if multiple errors are not useful to the caller. We could instead create an error that implements the Unwrap() []error method which can be used to retrieve multiple errors.

// Existing signature
RenderAndReload() ([]byte, Document, *DocumentModel[v3high.Document], []error)
// Would become
RenderAndReload() ([]byte, Document, *DocumentModel[v3high.Document], error)

Example implementation

type MultiError struct {
	errs []error
}

func (e *MultiError) Error() string {
	var b []byte
	for i, err := range e.errs {
		if i > 0 {
			b = append(b, '\n')
		}
		b = append(b, err.Error()...)
	}
	return string(b)
}

func (e *MultiError) Unwrap() []error {
	return e.errs
}

The conversion would be easy, but would break the compatibility. As such it should probably wait for a v1 or v2 release.

See https://pkg.go.dev/errors#Join

[daveshanley]

Ah yes, I thought the same thing when I saw the release notes for 1.20.

Yes this is a good idea, adding it to the backlog.

[n0rig]

@daveshanley is this still the approach you want to be followed? If so, I can work on this.

[jxsl13]

I'd suggest just using errors.Join and return a single error.

[daveshanley]

I would avoid working on this until the library is ready for 1.0, it's a major breaking change to the top level of the library in terms of signature. It's a small change with big consequences.

[stevenh]

@daveshanley I would suggest doing it ASAP as that will result in less people having to alter their code.