Add option for including operationName as a query parameter

docs/CHANGELOG.md

@@ -24,6 +24,7 @@ When releasing a new version:
 
 ### New features:
 
+- The new `graphql.WithOperationNameParam` allows clients to be created that include `operationName` as a query parameter.
 - The new `optional: generic` allows using a generic type to represent optionality. See the [documentation](genqlient.yaml) for details.
 - For schemas with enum values that differ only in casing, it's now possible to disable smart-casing in genqlient.yaml; see the [documentation](genqlient.yaml) for `casing` for details.
 

docs/FAQ.md

@@ -36,6 +36,19 @@ The URL requested will be:
 
 The client does not support mutations, and will return an error if passed a request that attempts one.
 
+###  … include operationName as a query parameter?
+
+`graphql.NewClient` support the option `graphql.WithOperationNameParam`, which will add `?operationName=...` to the request's query parameters.
+
+```go
+ctx := context.Background()
+client := graphql.NewClient("https://api.github.com/graphql", http.DefaultClient, graphql.WithOperationNameParam)
+resp, err := getUser(ctx, client, "benjaminjkraft")
+fmt.Println(resp.User.Name, err)
+```
+
+
+
 ### … use an API that requires authentication?
 
 When you call `graphql.NewClient`, pass in an HTTP client that adds whatever authentication headers you need (typically by wrapping the client's `Transport`).  For example:

graphql/client.go

@@ -41,9 +41,15 @@ type Client interface {
 }
 
 type client struct {
-	httpClient Doer
-	endpoint   string
-	method     string
+	httpClient             Doer
+	endpoint               string
+	method                 string
+	withOperationNameParam bool
+}
+
+// WithOperationNameParam allows operationName to be included as a query parameter.
+func WithOperationNameParam(c *client) {
+	c.withOperationNameParam = true
 }
 
 // NewClient returns a [Client] which makes requests to the given endpoint,
@@ -58,8 +64,8 @@ type client struct {
 // example.
 //
 // [example/main.go]: https://github.com/Khan/genqlient/blob/main/example/main.go#L12-L20
-func NewClient(endpoint string, httpClient Doer) Client {
-	return newClient(endpoint, httpClient, http.MethodPost)
+func NewClient(endpoint string, httpClient Doer, options ...func(*client)) Client {
+	return newClient(endpoint, httpClient, http.MethodPost, options...)
 }
 
 // NewClientUsingGet returns a [Client] which makes GET requests to the given
@@ -83,11 +89,19 @@ func NewClientUsingGet(endpoint string, httpClient Doer) Client {
 	return newClient(endpoint, httpClient, http.MethodGet)
 }
 
-func newClient(endpoint string, httpClient Doer, method string) Client {
+func newClient(endpoint string, httpClient Doer, method string, options ...func(*client)) Client {
 	if httpClient == nil || httpClient == (*http.Client)(nil) {
 		httpClient = http.DefaultClient
 	}
-	return &client{httpClient, endpoint, method}
+	c := &client{
+		httpClient: httpClient,
+		endpoint:   endpoint,
+		method:     method,
+	}
+	for _, opt := range options {
+		opt(c)
+	}
+	return c
 }
 
 // Doer encapsulates the methods from [*http.Client] needed by [Client].
@@ -178,14 +192,31 @@ func (c *client) MakeRequest(ctx context.Context, req *Request, resp *Response)
 }
 
 func (c *client) createPostRequest(req *Request) (*http.Request, error) {
+	parsedURL, err := url.Parse(c.endpoint)
+	if err != nil {
+		return nil, err
+	}
+
+	queryParams := parsedURL.Query()
+	queryUpdated := false
+
+	if c.withOperationNameParam && req.OpName != "" {
+		queryParams.Set("operationName", req.OpName)
+		queryUpdated = true
+	}
+
+	if queryUpdated {
+		parsedURL.RawQuery = queryParams.Encode()
+	}
+
 	body, err := json.Marshal(req)
 	if err != nil {
 		return nil, err
 	}
 
 	httpReq, err := http.NewRequest(
 		c.method,
-		c.endpoint,
+		parsedURL.String(),
 		bytes.NewReader(body))
 	if err != nil {
 		return nil, err

internal/integration/integration_test.go

@@ -107,6 +107,7 @@ func TestVariables(t *testing.T) {
 	// worry about it.
 	clients := []graphql.Client{
 		graphql.NewClient(server.URL, http.DefaultClient),
+		graphql.NewClient(server.URL, http.DefaultClient, graphql.WithOperationNameParam),
 		graphql.NewClientUsingGet(server.URL, http.DefaultClient),
 	}
 

internal/integration/roundtrip.go

@@ -104,7 +104,11 @@ func (c *roundtripClient) MakeRequest(ctx context.Context, req *graphql.Request,
 }
 
 func newRoundtripClients(t *testing.T, endpoint string) []graphql.Client {
-	return []graphql.Client{newRoundtripClient(t, endpoint), newRoundtripGetClient(t, endpoint)}
+	return []graphql.Client{
+		newRoundtripClient(t, endpoint),
+		newRoundtripClientWithOptions(t, endpoint),
+		newRoundtripGetClient(t, endpoint),
+	}
 }
 
 func newRoundtripClient(t *testing.T, endpoint string) graphql.Client {
@@ -117,6 +121,16 @@ func newRoundtripClient(t *testing.T, endpoint string) graphql.Client {
 	}
 }
 
+func newRoundtripClientWithOptions(t *testing.T, endpoint string) graphql.Client {
+	transport := &lastResponseTransport{wrapped: http.DefaultTransport}
+	httpClient := &http.Client{Transport: transport}
+	return &roundtripClient{
+		wrapped:   graphql.NewClient(endpoint, httpClient, graphql.WithOperationNameParam),
+		transport: transport,
+		t:         t,
+	}
+}
+
 func newRoundtripGetClient(t *testing.T, endpoint string) graphql.Client {
 	transport := &lastResponseTransport{wrapped: http.DefaultTransport}
 	httpClient := &http.Client{Transport: transport}