Implement June 2018 error spec

[ccbrown]

This implements section 7.1.2 of the June 2018 spec.

Paths are now added to errors:

  "errors": [
    {
      "message": "Name for character with ID 1002 could not be fetched.",
      "locations": [ { "line": 6, "column": 7 } ],
      "path": [ "hero", "heroFriends", 1, "name" ]
    }
  ],

If an error can be associated to a particular field in the GraphQL result, it must contain an entry with the key path that details the path of the response field which experienced the error.

And extensions are now present when resolve functions return implementations of gqlerrors.ExtendedError:

  "errors": [
    {
      "message": "Name for character with ID 1002 could not be fetched.",
      "locations": [ { "line": 6, "column": 7 } ],
      "path": [ "hero", "heroFriends", 1, "name" ],
      "extensions": {
        "code": "CAN_NOT_FETCH_BY_ID",
        "timestamp": "Fri Feb 9 14:33:09 UTC 2018"
      }
    }
  ]

GraphQL services may provide an additional entry to errors with key extensions. This entry, if set, must have a map as its value. This entry is reserved for implementors to add additional information to errors however they see fit, and there are no additional restrictions on its contents.

It's very much a transliteration of the JavaScript implementation. No creativity was involved here. I've gone through all the tests and painstakingly updated them. Those in addition to some new tests cover the changes extremely well.

This addresses #200, #259, #351, #109, and kinda sorta #312.

[coveralls]

Coverage increased (+0.03%) to 91.765% when pulling 8752c8e on ccbrown:error-spec-catchup into 086b3bf on graphql-go:master.

[appleboy]

LGTM. @chris-ramon When to merge this feature?

[chris-ramon]

I think we should be naming this function Extensions to avoid extra suffix.
It is addressed in a new PR: #364

[chris-ramon]

Thanks a lot @ccbrown this looks very good to me! 👍 — Also thanks @appleboy for reviewing it as well. 🚢

[SebScoFr]

When do you plan to release this? We would love to have that change available 👍

[chris-ramon]

When do you plan to release this? We would love to have that change available

Hi @SebScoFr, thanks a lot for using the lib!

I've just created a new release v0.7.6 which contains this PR along some other great improvements. 🚢

[jphuc96]

@ccbrown I am working on this "extension", may I have a simple example that implement this feature, as I find some difficult to implement the ExtendedError interface ? Thanks for the great PR

[ccbrown]

@jphuc96 here's an example:

type ErrorWithCode struct {
    Message string
    Code string
}

func (err *ErrorWithCode) Error() string {
    return err.Message
}

func (err *ErrorWithCode) Extensions() map[string]interface{} {
    return map[string]interface{}{
        "code": err.Code,
    }
}

// Not required but recommended:
// Makes sure at compile time that ErrorWithCode implements gqlerrors.ExtendedError
var _ gqlerrors.ExtendedError = (*ErrorWithCode)(nil)

Then in your resolver you can do something like this:

return nil, &ErrorWithCode{"Not authorized.", "not_authorized"}

[jphuc96]

@jphuc96 here's an example:

type ErrorWithCode struct {
    Message string
    Code string
}

func (err *ErrorWithCode) Error() string {
    return err.Message
}

func (err *ErrorWithCode) Extensions() map[string]interface{} {
    return map[string]interface{}{
        "code": err.Code,
    }
}

// Not required but recommended:
// Makes sure at compile time that ErrorWithCode implements gqlerrors.ExtendedError
var _ gqlerrors.ExtendedError = (*ErrorWithCode)(nil)

Then in your resolver you can do something like this:

return nil, &ErrorWithCode{"Not authorized.", "not_authorized"}

that really did the trick, thanks for saving me @ccbrown 👍 👍 👍

[appleboy]

@jphuc96 You can ref the example code: https://github.com/go-ggz/ggz/blob/d3d22a347506cbe36ef24bdd229efb74a56c0541/pkg/errors/errors.go#L1

// Error applicational
type Error struct {
	Type    Type
	Message string
	cause   error
}

// Error message
func (e *Error) Error() string {
	return e.Message
}

// Cause of the original error
func (e *Error) Cause() string {
	if e.cause != nil {
		return e.cause.Error()
	}

	return ""
}

// Extensions for graphQL extension
func (e *Error) Extensions() map[string]interface{} {
	if e.cause != nil {
		log.Error().Err(e.cause).Msg("graphql error report")
	}

	return map[string]interface{}{
		"code": e.Type.Code(),
		"type": e.Type,
	}
}