When a GraphQL service receives a request, it must return a well-formed response. The service's response describes the result of executing the requested operation if successful, and describes any errors raised during the request.
A response may contain both a partial response as well as a list of errors in the case that any field error was raised on a field and was replaced with {null}.
A response to a GraphQL request must be a map.
If the request raised any errors, the response map must contain an entry with
key errors. The value of this entry is described in the "Errors" section. If
the request completed without raising any errors, this entry must not be
present.
If the request included execution, the response map must contain an entry with
key data. The value of this entry is described in the "Data" section. If the
request failed before execution, due to a syntax error, missing information, or
validation error, this entry must not be present.
The response map may also contain an entry with key extensions. This entry, if
set, must have a map as its value. This entry is reserved for implementers to
extend the protocol however they see fit, and hence there are no additional
restrictions on its contents.
To ensure future changes to the protocol do not break existing services and clients, the top level response map must not contain any entries other than the three described above.
Note: When errors is present in the response, it may be helpful for it to
appear first when serialized to make it more clear when errors are present in a
response during debugging.
The data entry in the response will be the result of the execution of the
requested operation. If the operation was a query, this output will be an object
of the query root operation type; if the operation was a mutation, this output
will be an object of the mutation root operation type.
If an error was raised before execution begins, the data entry should not be
present in the result.
If an error was raised during the execution that prevented a valid response, the
data entry in the response should be null.
The errors entry in the response is a non-empty list of errors raised during
the request, where each error is a map of data described by the error result
format below.
If present, the errors entry in the response must contain at least one error.
If no errors were raised during the request, the errors entry must not be
present in the result.
If the data entry in the response is not present, the errors entry must be
present. It must contain at least one request error indicating why no data was
able to be returned.
If the data entry in the response is present (including if it is the value
{null}), the errors entry must be present if and only if one or more field
error was raised during execution.
Request Errors
:: A request error is an error raised during a request which results in no response data. Typically raised before execution begins, a request error may occur due to a parse grammar or validation error in the Document, an inability to determine which operation to execute, or invalid input values for variables.
A request error is typically the fault of the requesting client.
If a request error is raised, the data entry in the response must not be
present, the errors entry must include the error, and request execution should
be halted.
Field Errors
:: A field error is an error raised during the execution of a particular field which results in partial response data. This may occur due to an internal error during value resolution or failure to coerce the resulting value.
A field error is typically the fault of a GraphQL service.
If a field error is raised, execution attempts to continue and a partial result
is produced (see Handling Field Errors). The
data entry in the response must be present. The errors entry should include
this error.
Error Result Format
Every error must contain an entry with the key message with a string
description of the error intended for the developer as a guide to understand and
correct the error.
If an error can be associated to a particular point in the requested GraphQL
document, it should contain an entry with the key locations with a list of
locations, where each location is a map with the keys line and column, both
positive numbers starting from 1 which describe the beginning of an associated
syntax element.
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. This allows clients to identify whether a
null result is intentional or caused by a runtime error.
If present, this field must be a list of path segments starting at the root of the response and ending with the field associated with the error. Path segments that represent fields must be strings, and path segments that represent list indices must be 0-indexed integers. If the error happens in an aliased field, the path to the error must use the aliased name, since it represents a path in the response, not in the request.
For example, if fetching one of the friends' names fails in the following operation:
{
hero(episode: $episode) {
name
heroFriends: friends {
id
name
}
}
}The response might look like:
{
"errors": [
{
"message": "Name for character with ID 1002 could not be fetched.",
"locations": [{ "line": 6, "column": 7 }],
"path": ["hero", "heroFriends", 1, "name"]
}
],
"data": {
"hero": {
"name": "R2-D2",
"heroFriends": [
{
"id": "1000",
"name": "Luke Skywalker"
},
{
"id": "1002",
"name": null
},
{
"id": "1003",
"name": "Leia Organa"
}
]
}
}
}If the field which experienced an error was declared as Non-Null, the null
result will bubble up to the next nullable field. In that case, the path for
the error should include the full path to the result field where the error was
raised, even if that field is not present in the response.
For example, if the name field from above had declared a Non-Null return
type in the schema, the result would look different but the error reported would
be the same:
{
"errors": [
{
"message": "Name for character with ID 1002 could not be fetched.",
"locations": [{ "line": 6, "column": 7 }],
"path": ["hero", "heroFriends", 1, "name"]
}
],
"data": {
"hero": {
"name": "R2-D2",
"heroFriends": [
{
"id": "1000",
"name": "Luke Skywalker"
},
null,
{
"id": "1003",
"name": "Leia Organa"
}
]
}
}
}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 implementers to add additional information to errors however they
see fit, and there are no additional restrictions on its contents.
{
"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 should not provide any additional entries to the error format since they could conflict with additional entries that may be added in future versions of this specification.
Note: Previous versions of this spec did not describe the extensions entry for
error formatting. While non-specified entries are not violations, they are still
discouraged.
{
"errors": [
{
"message": "Name for character with ID 1002 could not be fetched.",
"locations": [{ "line": 6, "column": 7 }],
"path": ["hero", "heroFriends", 1, "name"],
"code": "CAN_NOT_FETCH_BY_ID",
"timestamp": "Fri Feb 9 14:33:09 UTC 2018"
}
]
}GraphQL does not require a specific serialization format. However, clients should use a serialization format that supports the major primitives in the GraphQL response. In particular, the serialization format must at least support representations of the following four primitives:
- Map
- List
- String
- Null
A serialization format should also support the following primitives, each representing one of the common GraphQL scalar types, however a string or simpler primitive may be used as a substitute if any are not directly supported:
- Boolean
- Int
- Float
- Enum Value
This is not meant to be an exhaustive list of what a serialization format may encode. For example custom scalars representing a Date, Time, URI, or number with a different precision may be represented in whichever relevant format a given serialization format may support.
JSON is the most common serialization format for GraphQL. Though as mentioned above, GraphQL does not require a specific serialization format.
When using JSON as a serialization of GraphQL responses, the following JSON values should be used to encode the related GraphQL values:
| GraphQL Value | JSON Value |
|---|---|
| Map | Object |
| List | Array |
| Null | {null} |
| String | String |
| Boolean | {true} or {false} |
| Int | Number |
| Float | Number |
| Enum Value | String |
Note: For consistency and ease of notation, examples of responses are given in JSON format throughout this document.
Since the result of evaluating a selection set is ordered, the serialized Map of results should preserve this order by writing the map entries in the same order as those fields were requested as defined by selection set execution. Producing a serialized response where fields are represented in the same order in which they appear in the request improves human readability during debugging and enables more efficient parsing of responses if the order of properties can be anticipated.
Serialization formats which represent an ordered map should preserve the order of requested fields as defined by {CollectFields()} in the Execution section. Serialization formats which only represent unordered maps but where order is still implicit in the serialization's textual order (such as JSON) should preserve the order of requested fields textually.
For example, if the request was { name, age }, a GraphQL service responding in
JSON should respond with { "name": "Mark", "age": 30 } and should not respond
with { "age": 30, "name": "Mark" }.
While JSON Objects are specified as an
unordered collection of key-value pairs
the pairs are represented in an ordered manner. In other words, while the JSON
strings { "name": "Mark", "age": 30 } and { "age": 30, "name": "Mark" }
encode the same value, they also have observably different property orderings.
Note: This does not violate the JSON spec, as clients may still interpret objects in the response as unordered Maps and arrive at a valid value.