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 execution error was raised and replaced with {null}.
:: A GraphQL request returns a response. A response is either an execution result, a response stream, or a request error result.
:: A GraphQL request returns an execution result when the GraphQL operation is a query or mutation and the request included execution. Additionally, for each event in a subscription's source stream, the response stream will emit an execution result.
An execution result must be a map.
The execution result must contain an entry with key {"data"}. The value of this entry is described in the "Data" section.
If execution raised any errors, the execution result must contain an entry with key {"errors"}. The value of this entry must be a non-empty list of execution error raised during execution. Each error must be a map as described in the "Errors" section below. If the request completed without raising any errors, this entry must not be present.
Note: When {"errors"} is present in an execution result, it may be helpful for it to appear first when serialized to make it more apparent that errors are present.
The execution result may also contain an entry with key extensions. The
value of this entry is described in the "Extensions" section.
:: A GraphQL request returns a response stream when the GraphQL operation is a subscription and the request included execution. A response stream must be a stream of execution result.
:: A GraphQL request returns a request error result when one or more request error are raised, causing the request to fail before execution. This request will result in no response data.
Note: A request error may be raised before execution due to missing information, syntax errors, validation failure, coercion failure, or any other reason the implementation may determine should prevent the request from proceeding.
A request error result must be a map.
The request error result map must contain an entry with key {"errors"}. The value of this entry must be a non-empty list of request error raised during the request. It must contain at least one request error indicating why no data was able to be returned. Each error must be a map as described in the "Errors" section below.
Note: It may be helpful for the {"errors"} key to appear first when serialized to make it more apparent that errors are present.
The request error result map must not contain an entry with key {"data"}.
The request error result map may also contain an entry with key extensions.
The value of this entry is described in the "Extensions" section.
:: A response position is a uniquely identifiable position in the response data produced during execution. It is either a direct entry in the {resultMap} of a {ExecuteSelectionSet()}, or it is a position in a (potentially nested) List value. Each response position is uniquely identifiable via a response path.
:: A response path uniquely identifies a response position via a list of path segments (response names or list indices) starting at the root of the response and ending with the associated response position.
The value for a response path must be a list of path segments. Path segments that represent field response name must be strings, and path segments that represent list indices must be 0-indexed integers. If a path segment is associated with an aliased field it must use the aliased name, since it represents a path in the response, not in the request.
When a response path is present on an error result, it identifies the response position which raised the error.
A single field execution may result in multiple response positions. For example,
{
hero(episode: $episode) {
name
friends {
name
}
}
}The hero's name would be found in the response position identified by the
response path ["hero", "name"]. The List of the hero's friends would be
found at ["hero", "friends"], the hero's first friend at
["hero", "friends", 0] and that friend's name at
["hero", "friends", 0, "name"].
The {"data"} entry in the execution result 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.
The response data is the result of accumulating the resolved result of all response positions during execution.
If an error was raised before execution begins, the response must be a request error result which will result in no response data.
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 execution result or request error result 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.
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 response must be a request error result. The {"data"} entry in this map must not be present, the {"errors"} entry must include the error, and request execution should be halted.
Execution Errors
:: An execution error is an error raised during the execution of a particular field which results in partial response data. This may occur due to failure to coerce the arguments for the field, an internal error during value resolution, or failure to coerce the resulting value.
Note: In previous versions of this specification execution error was called field error.
An execution error is typically the fault of a GraphQL service.
An execution error must occur at a specific response position, and may occur in any response position. The response position of an execution error is indicated via a response path in the error response's {"path"} entry.
When an execution error is raised at a given response position, then that response position must not be present within the response {"data"} entry (except {null}), and the {"errors"} entry must include the error. Nested execution is halted and sibling execution attempts to continue, producing partial result (see Handling Execution Errors).
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"} with a response path which describes the response position which raised the error. This allows clients to identify whether a {null} resolved result is a true value or the result of an execution error.
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"
}
]
}The {"extensions"} entry in an execution result or request error result, 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 execution result and request error result maps must not contain any entries other than those described above. Clients must ignore any entries other than those described above.
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.