Provide access to original error from json.Unmarshal

[aakhan1]

What feature or capability would you like?

I would like to gain access the Offset property when a json syntax error occurs so I can report the line and column of the error.

schemaErrors, err := rs.ValidateBytes(ctx, document)
if err!=nil {
	syntaxError := err.(*json.SyntaxError)
	fmt.Println("The offset is:", syntaxError.Offset)
}

Unfortunately, this results in a panic because the rs.ValidateBytes returns a *errors.errorString
panic: interface conversion: error is *errors.errorString, not *json.SyntaxError

Do you have a proposed solution?

Would it be possible to change the implementation of rs.ValidateBytes to return the error as a wrapped error?

Change the %s to %w? Then I can unwrap the error and get what I need.

func (s *Schema) ValidateBytes(ctx context.Context, data []byte) ([]KeyError, error) {
	var doc interface{}
	if err := json.Unmarshal(data, &doc); err != nil {
		return nil, fmt.Errorf("error parsing JSON bytes: %w", err) // <--- change from %s to %w
	}
	vs := s.Validate(ctx, doc)
	return *vs.Errs, nil
}

Or provide a method on the error object where the original error can be accessed.

Have you considered any alternative solutions or workarounds?

I have implemented my own json.Unmarshal call before calling rs.ValidateBytes, but I feel this adds a performance delay unnecessarily.

[aakhan1]

@Arqu I'd like to work on this if possible.

[Arqu]

@aakhan1 Absolutely appreciated, as you see time is tight, and help like this really polishes some of the rough edges. A PR is more than welcome. Happy hacktober :)

[Arqu]

Done in #85