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230 changes: 25 additions & 205 deletions spec/GraphQLOverHTTP.md
Original file line number Diff line number Diff line change
Expand Up @@ -183,10 +183,10 @@ using the JSON encoding for GraphQL requests:

And for a _GraphQL response_:

| Name | Description |
| ----------------------------------- | ------------------------------------------------------------------ |
| `application/graphql-response+json` | The preferred type for server responses; better HTTP compatibility |
| `application/json` | An alternative type for responses (to support legacy clients) |
| Name | Description |
| ----------------------------------- | ---------------------------------------- |
| `application/graphql-response+json` | The preferred type for server responses |
| `application/json` | An alternative type for responses |
Comment thread
michaelstaib marked this conversation as resolved.
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For details of the shapes of these JSON payloads, please see
[Request](#sec-Request) and [Response](#sec-Response).
Expand Down Expand Up @@ -257,20 +257,12 @@ client gets something useful, it needs to indicate the media types it supports.
The client MUST include the media type `application/graphql-response+json` in
the `Accept` header.

If the client knows that the server supports
`application/graphql-response+json`, it is RECOMMENDED that the client set the
`Accept` header to `application/graphql-response+json`. Otherwise, to maximize
compatibility the client SHOULD include the media type `application/json` in the
`Accept` header and it is RECOMMENDED that the client set the `Accept` header to
`application/graphql-response+json, application/json;q=0.9`.
It is RECOMMENDED that the client set the `Accept` header to
`application/graphql-response+json`.
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Note: The `q=0.9` parameter tells content negotiation that `application/json`
should only be used if `application/graphql-response+json` is not supported.

The `application/graphql-response+json` media type adds improved support for
HTTP status codes compared to the legacy `application/json` media type. When
accepting both media types, the client SHOULD indicate it prefers
`application/graphql-response+json` over `application/json`.
The client MAY additionally include the media type `application/json` in the
`Accept` header. When accepting both media types, the client SHOULD indicate it
prefers `application/graphql-response+json` over `application/json`.
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## GET

Expand Down Expand Up @@ -461,33 +453,13 @@ one of the media types it has requested, hence `406 Not Acceptable` being the
recommended response. However, the server authors may know better about the
specific clients consuming their endpoint, thus both approaches are permitted.

A server MUST support responses using at least one of the official GraphQL
response media types.

For maximal compatibility, a _server_ SHOULD support using both the
`application/json` and the `application/graphql-response+json` media types for
responses.

Each newly created or updated GraphQL _server_ SHOULD support responses using
the `application/graphql-response+json` media type.

:: A _legacy server_ is a _server_ that does not support responses using the
A _server_ MUST support responses using the
`application/graphql-response+json` media type.

Note: Prior to this specification, the media type `application/json` was in wide
use for the HTTP response payload type. Unfortunately this means clients cannot
trust responses from the server that do not use an HTTP 2xx status code (since
these replies may come from non-compliant HTTP servers or proxies somewhere in
the request chain). For this reason, this specification introduces the
`application/graphql-response+json` media type on responses; however support for
this new media type is optional to allow legacy servers time to transition.

A server MAY choose to not support the `application/json` response media type,
however doing so may limit compatibility with existing clients, so it is only
recommended when creating a new GraphQL service.
A server MAY additionally support the `application/json` response media type.

Note: Servers may wish to enforce that clients use the
`application/graphql-response+json` data type so that related HTTP tooling may
Note: Servers may wish to only support the
`application/graphql-response+json` media type so that related HTTP tooling may
utilize the HTTP status codes of responses without having to be GraphQL-aware.

## Validation
Expand Down Expand Up @@ -515,144 +487,12 @@ execution regardless of validation errors.
## Status Codes

In case of errors that completely prevent the generation of a well-formed
_GraphQL response_, the server SHOULD respond with the appropriate status code
_GraphQL response_, the server MUST respond with the appropriate status code
depending on the concrete error condition, and MUST NOT respond with a `2xx`
status code when using the `application/graphql-response+json` media type.
status code.

Note: Typically the appropriate status code will be `400` (Bad Request).

Note: This rule is "should" to maintain compatibility with legacy servers which
can return 200 status codes even when this type of error occurs, but only when
not using the `application/graphql-response+json` media type.

Otherwise, the status codes depends on the media type with which the GraphQL
response will be served:

### application/json

This section only applies when the response body is to use the
`application/json` media type.

The server SHOULD use the `200` status code for every response to a well-formed
_GraphQL-over-HTTP request_, independent of any _GraphQL request error_ or
_GraphQL field error_ raised.

If the response uses a non-`200` status code then the client MUST NOT rely on
the body to be a well-formed _GraphQL response_.

Note: A status code in the `4xx` or `5xx` ranges or status code `203` (and maybe
others) could originate from an intermediary; since the client cannot determine
if an `application/json` response with arbitrary status code is a well-formed
_GraphQL response_ (because it cannot trust the source) the server must use
`200` status code to guarantee to the client that the response has not been
generated or modified by an intermediary. See
[processing a response](#sec-Processing-a-response) for more details.

If the _GraphQL response_ contains a non-null {data} entry then the server MUST
use the `200` status code.

Note: This indicates that no _GraphQL request error_ was raised, though one or
more _GraphQL field error_ may have been raised this is still a successful
execution - see "partial response" in the GraphQL specification.

The server SHOULD NOT use a `4xx` or `5xx` status code for a response to a
well-formed _GraphQL-over-HTTP request_.

Note: For compatibility with legacy servers, this specification allows the use
of `4xx` or `5xx` status codes for a failed well-formed _GraphQL-over-HTTP
request_ where the response uses the `application/json` media type, but it is
strongly discouraged. To use `4xx` and `5xx` status codes in these situations,
please use the `application/graphql-response+json` media type.

If the URL is not used for other purposes, the server SHOULD use a `4xx` status
code to respond to a request that is not a well-formed _GraphQL-over-HTTP
request_.

Note: For compatibility with legacy servers, this specification allows the use
of `2xx` or `5xx` status codes when responding to invalid requests using the
`application/json` media type, but it is strongly discouraged.

Note: URLs that enable GraphQL requests may enable other types of requests - see
the [URL](#url) section.

#### Examples

The following examples provide guidance on how to deal with specific error cases
when using the `application/json` media type to encode the response body:

##### JSON parsing failure

For example a POST request body of `NONSENSE` or `{"query":` (note: invalid
JSON).

Requests that the server cannot interpret SHOULD result in status code `400`
(Bad Request).

##### Invalid parameters

For example a POST request body of `{"qeury": "{__typename}"}` (note: typo) or
`{"query": "query Q ($i:Int!) { q(i: $i) }", "variables": [7]}` (note: invalid
shape for `variables`).

A request that does not constitute a well-formed _GraphQL-over-HTTP request_
SHOULD result in status code `400` (Bad Request).

##### Document parsing failure

For example a POST request body of `{"query": "{"}`.

Requests where the _GraphQL document_ cannot be parsed SHOULD result in status
code `200` (Okay).

##### Document validation failure

If a request fails to pass _GraphQL validation_, the server SHOULD NOT execute
the request and SHOULD return a status code of `200` (Okay).

##### Operation cannot be determined

If [GetOperation()](<https://spec.graphql.org/draft/#GetOperation()>) raises a
_GraphQL request error_, the server SHOULD NOT execute the request and SHOULD
return a status code of `200` (Okay).

##### Variable coercion failure

If
[CoerceVariableValues()](<https://spec.graphql.org/draft/#CoerceVariableValues()>)
raises a _GraphQL request error_, the server SHOULD NOT execute the request and
SHOULD return a status code of `200` (Okay).

For example the well-formed GraphQL-over-HTTP request:

```json
{
"query": "query getItemName($id: ID!) { item(id: $id) { id name } }",
"variables": { "id": null }
}
```

would fail variable coercion as the value for `id` would fail to satisfy the
query document's expectation that `id` is non-null.

##### Field errors encountered during execution

If the operation is executed and no _GraphQL request error_ is raised then the
server SHOULD respond with a status code of `200` (Okay). This is the case even
if a _GraphQL field error_ is raised during
[GraphQL's ExecuteQuery()](<https://spec.graphql.org/draft/#ExecuteQuery()>) or
[GraphQL's ExecuteMutation()](<https://spec.graphql.org/draft/#ExecuteMutation()>).

<!--
When we add support for subscriptions,
[GraphQL's MapSourceToResponseEvent()](<https://spec.graphql.org/draft/#MapSourceToResponseEvent()>)
should be added to the above.
-->

### application/graphql-response+json

This section only applies when the response body is to use the
`application/graphql-response+json` media type.

If the _GraphQL response_ contains the {data} entry and it is not {null}, then
the server MUST reply with a `2xx` status code and SHOULD reply with `200`
status code.
Expand Down Expand Up @@ -690,27 +530,24 @@ pass validation, then the server SHOULD reply with `400` status code.
If the client is not permitted to issue the GraphQL request then the server
SHOULD reply with `403`, `401` or similar appropriate status code.

Note: When the response media type is `application/graphql-response+json`,
clients can rely on the response being a well-formed _GraphQL response_
Note: Clients can rely on the response being a well-formed _GraphQL response_
regardless of the status code. Intermediary servers may use the status code to
determine the status of the _GraphQL response_ without needing to process the
response body.

#### Examples
### Examples

The following examples provide guidance on how to deal with specific error cases
when using the `application/graphql-response+json` media type to encode the
response body:
The following examples provide guidance on how to deal with specific error cases:

##### JSON parsing failure
#### JSON parsing failure

For example a POST request body of `NONSENSE` or `{"query":` (note: invalid
JSON).

Requests that the server cannot interpret should result in status code `400`
(Bad Request).

##### Invalid parameters
#### Invalid parameters

For example a POST request body of `{"qeury": "{__typename}"}` (note: typo) or
`{"query": "query Q ($i:Int!) { q(i: $i) }", "variables": [7]}` (note: invalid
Expand All @@ -719,32 +556,32 @@ shape for `variables`).
A request that does not constitute a well-formed _GraphQL-over-HTTP request_
SHOULD result in status code `400` (Bad Request).

##### Document parsing failure
#### Document parsing failure

For example a POST request body of `{"query": "{"}`.

Requests where the _GraphQL document_ cannot be parsed should result in status
code `400` (Bad Request).

##### Document validation failure
#### Document validation failure

If a request fails _GraphQL validation_, the server SHOULD return a status code
of `400` (Bad Request) without proceeding to GraphQL execution.

##### Operation cannot be determined
#### Operation cannot be determined

If [GetOperation()](<https://spec.graphql.org/draft/#GetOperation()>) raises a
_GraphQL request error_, the server SHOULD NOT execute the request and SHOULD
return a status code of `400` (Bad Request).

##### Variable coercion failure
#### Variable coercion failure

If
[CoerceVariableValues()](<https://spec.graphql.org/draft/#CoerceVariableValues()>)
raises a _GraphQL request error_, the server SHOULD NOT execute the request and
SHOULD return a status code of `400` (Bad Request).

##### Field errors encountered during execution
#### Field errors encountered during execution

If the operation is executed and no _GraphQL request error_ is raised then the
server SHOULD respond with a status code of `200` (Okay). This is the case even
Expand All @@ -768,23 +605,6 @@ response; it still indicates successful execution.
This section of the specification is non-normative, even where the words and
phrases specified in RFC2119 are used.

## Processing a response

In some cases, the response received by a client may not originate from a
GraphQL service, but instead from an intermediary—such as an API gateway, proxy,
firewall or other middleware—that does not implement this specification. Such an
intermediary might produce the response to indicate an error, returning a
response with `4xx` or `5xx` status code and potentially using the standard
`application/json` media type to encode the reason for the error. Such a
response is unlikely to be a valid GraphQL response.

For this reason, a client application can rely on the response being a
well-formed _GraphQL response_ only if at least one of the following conditions
is met:

- the response media type is `application/graphql-response+json`, or
- the status code is `200`.

## Security

This specification focuses solely on the intersection of GraphQL and HTTP.
Expand Down
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