Add multipart/form-data transport to support file uploads

client.go

@@ -8,11 +8,15 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"mime"
+	"mime/multipart"
 	"net/http"
+	"net/textproto"
 	"os"
 	"strings"
 	"time"
 
+	"github.com/99designs/gqlgen/graphql"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/vektah/gqlparser/v2/ast"
 	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
@@ -131,11 +135,11 @@ func (c *GraphQLClient) Request(ctx context.Context, url string, request *Reques
 		return err
 	}
 
-	var buf bytes.Buffer
-	if err := json.NewEncoder(&buf).Encode(request); err != nil {
+	buf, contentType, err := request.requestBody()
+	if err != nil {
 		return traceErr(fmt.Errorf("unable to encode request body: %w", err))
-	}
 
+	}
 	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, &buf)
 	if err != nil {
 		return traceErr(fmt.Errorf("unable to create request: %w", err))
@@ -145,7 +149,7 @@ func (c *GraphQLClient) Request(ctx context.Context, url string, request *Reques
 		httpReq.Header = request.Headers.Clone()
 	}
 
-	httpReq.Header.Set("Content-Type", "application/json; charset=utf-8")
+	httpReq.Header.Set("Content-Type", contentType)
 	httpReq.Header.Set("Accept", "application/json")
 
 	if c.UserAgent != "" {
@@ -246,6 +250,88 @@ func (r *Request) WithVariables(variables map[string]interface{}) *Request {
 	return r
 }
 
+// isMultipart returns true if the request contains a graphql.Upload object
+// implying that the downstream request needs to be a multipart/form-data request
+func (r *Request) isMultipart() bool {
+	stack := []map[string]any{r.Variables}
+	for len(stack) > 0 {
+		currentItem := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+		for _, v := range currentItem {
+			switch v := v.(type) {
+			case graphql.Upload, *graphql.Upload, []graphql.Upload, []*graphql.Upload:
+				return true
+			case map[string]any:
+				stack = append(stack, v)
+			}
+		}
+	}
+	return false
+}
+
+func (r *Request) requestBody() (bytes.Buffer, string, error) {
+	var buf bytes.Buffer
+	var err error
+	contentType := "application/json; charset=utf-8"
+	if r.isMultipart() {
+		buf, contentType, err = multipartBody(r)
+		if err != nil {
+			return buf, "", fmt.Errorf("unable to encode multipart request body: %w", err)
+		}
+		return buf, contentType, nil
+	}
+	if err = json.NewEncoder(&buf).Encode(r); err != nil {
+		return buf, "", fmt.Errorf("unable to encode request body: %w", err)
+	}
+	return buf, contentType, nil
+}
+
+func multipartBody(r *Request) (bytes.Buffer, string, error) {
+	files, fileMap := prepareUploadsFromVariables(r.Variables)
+
+	var buf bytes.Buffer
+	mpw := multipart.NewWriter(&buf)
+	fw, err := mpw.CreateFormField("operations")
+	if err != nil {
+		return buf, "", err
+	}
+	if err = json.NewEncoder(fw).Encode(r); err != nil {
+		return buf, "", err
+	}
+	fw, err = mpw.CreateFormField("map")
+	if err != nil {
+		return buf, "", err
+	}
+	if err = json.NewEncoder(fw).Encode(fileMap); err != nil {
+		return buf, "", err
+	}
+	for fileIndex := range fileMap {
+		h := make(textproto.MIMEHeader)
+		h.Set("Content-Disposition", mime.FormatMediaType("form-data", map[string]string{
+			"name":     fileIndex,
+			"filename": files[fileIndex].Filename,
+		}))
+		if ct := files[fileIndex].ContentType; ct != "" {
+			h.Set("Content-Type", files[fileIndex].ContentType)
+		} else {
+			h.Set("Content-Type", "application/octet-stream")
+		}
+		innerFw, fileErr := mpw.CreatePart(h)
+		if fileErr != nil {
+			return buf, "", fileErr
+		}
+		_, ioErr := io.Copy(innerFw, files[fileIndex].File)
+		if ioErr != nil {
+			return buf, "", ioErr
+		}
+	}
+	err = mpw.Close()
+	if err != nil {
+		return buf, "", err
+	}
+	return buf, mpw.FormDataContentType(), nil
+}
+
 // Response is a GraphQL response
 type Response struct {
 	Errors GraphqlErrors `json:"errors"`
@@ -275,3 +361,60 @@ func (e GraphqlErrors) Error() string {
 func GenerateUserAgent(operation string) string {
 	return fmt.Sprintf("Bramble/%s (%s)", Version, operation)
 }
+
+func prepareUploadsFromVariables(variables map[string]any) (map[string]graphql.Upload, map[string][]string) {
+	type stackItem struct {
+		path string
+		data map[string]interface{}
+	}
+
+	stack := []stackItem{{path: "variables", data: variables}}
+
+	index := 0
+	fileMap := map[string][]string{}
+	files := map[string]graphql.Upload{}
+	for len(stack) > 0 {
+		currentItem := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+
+		for key, value := range currentItem.data {
+			currentPath := currentItem.path + "." + key
+
+			switch v := value.(type) {
+			case graphql.Upload, *graphql.Upload:
+				currentItem.data[key] = nil
+				fileIndex := fmt.Sprintf("file%d", index)
+				fileMap[fileIndex] = []string{currentPath}
+				index += 1
+				switch v := v.(type) {
+				case graphql.Upload:
+					files[fileIndex] = v
+				case *graphql.Upload:
+					files[fileIndex] = *v
+				}
+			case []graphql.Upload:
+				currentItem.data[key] = make([]*struct{}, len(v))
+				for i, file := range v {
+					elemPath := fmt.Sprintf("%s.%d", currentPath, i)
+					fileIndex := fmt.Sprintf("file%d", index)
+					fileMap[fileIndex] = []string{elemPath}
+					index += 1
+					files[fileIndex] = file
+				}
+			case []*graphql.Upload:
+				currentItem.data[key] = make([]*struct{}, len(v))
+				for i, file := range v {
+					elemPath := fmt.Sprintf("%s.%d", currentPath, i)
+					fileIndex := fmt.Sprintf("file%d", index)
+					fileMap[fileIndex] = []string{elemPath}
+					index += 1
+					files[fileIndex] = *file
+				}
+			case map[string]any:
+				stack = append(stack, stackItem{data: v, path: currentPath})
+			default:
+			}
+		}
+	}
+	return files, fileMap
+}

client_test.go

@@ -8,6 +8,7 @@ import (
 	"net/url"
 	"testing"
 
+	"github.com/99designs/gqlgen/graphql"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -102,3 +103,93 @@ func TestGraphqlClient(t *testing.T) {
 		assert.Equal(t, "response exceeded maximum size of 1 bytes", err.Error())
 	})
 }
+func TestMultipartClient(t *testing.T) {
+	nestedMap := map[string]any{
+		"node1": map[string]any{
+			"node11": map[string]any{
+				"leaf111": graphql.Upload{},
+				"leaf112": "someThing",
+				"node113": map[string]any{"leaf1131": graphql.Upload{}},
+			},
+			"leaf12": 42,
+			"leaf13": graphql.Upload{},
+		},
+		"node2": map[string]any{
+			"leaf21": false,
+			"node21": map[string]any{
+				"leaf211": &graphql.Upload{},
+			},
+		},
+		"node3": graphql.Upload{},
+		"node4": []graphql.Upload{{}, {}},
+		"node5": []*graphql.Upload{{}, {}},
+	}
+
+	t.Run("parseMultipartVariables", func(t *testing.T) {
+		_, fileMap := prepareUploadsFromVariables(nestedMap)
+		fileMapKeys := []string{}
+		fileMapValues := []string{}
+		for k, v := range fileMap {
+			fileMapKeys = append(fileMapKeys, k)
+			fileMapValues = append(fileMapValues, v...)
+		}
+		assert.ElementsMatch(t, fileMapKeys, []string{"file0", "file1", "file2", "file3", "file4", "file5", "file6", "file7", "file8"})
+		assert.ElementsMatch(t, fileMapValues, []string{
+			"variables.node1.node11.node113.leaf1131",
+			"variables.node1.node11.leaf111",
+			"variables.node1.leaf13",
+			"variables.node2.node21.leaf211",
+			"variables.node3",
+			"variables.node4.0",
+			"variables.node4.1",
+			"variables.node5.0",
+			"variables.node5.1",
+		})
+		assert.Equal(
+			t,
+			map[string]any{
+				"node1": map[string]any{
+					"node11": map[string]any{
+						"leaf111": nil,
+						"leaf112": "someThing",
+						"node113": map[string]any{"leaf1131": nil},
+					},
+					"leaf12": 42,
+					"leaf13": nil,
+				},
+				"node2": map[string]any{
+					"leaf21": false,
+					"node21": map[string]any{
+						"leaf211": nil,
+					},
+				},
+				"node3": nil,
+				"node4": []*struct{}{nil, nil},
+				"node5": []*struct{}{nil, nil},
+			},
+			nestedMap,
+		)
+	})
+
+	t.Run("multipart request", func(t *testing.T) {
+		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Write([]byte(`{ "data": {"root": "multipart response"} }`))
+		}))
+
+		c := NewClient()
+		req := &Request{Headers: make(http.Header)}
+		req.Headers.Set("Content-Type", "multipart/form-data")
+
+		var res struct {
+			Root string
+		}
+		err := c.Request(
+			context.Background(),
+			srv.URL,
+			req,
+			&res,
+		)
+		require.NoError(t, err)
+		assert.Equal(t, "multipart response", res.Root)
+	})
+}

config.go

@@ -52,6 +52,7 @@ type Config struct {
 	PollIntervalDuration   time.Duration
 	MaxRequestsPerQuery    int64           `json:"max-requests-per-query"`
 	MaxServiceResponseSize int64           `json:"max-service-response-size"`
+	MaxFileUploadSize      int64           `json:"max-file-upload-size"`
 	Telemetry              TelemetryConfig `json:"telemetry"`
 	Plugins                []PluginConfig
 	// Config extensions that can be shared among plugins

docker-compose.yaml

@@ -10,6 +10,16 @@ services:
       retries: 5
     expose:
       - 8080
+  gqlgen-multipart-file-upload-service:
+    build:
+      context: examples/gqlgen-multipart-file-upload-service
+    healthcheck: &healthcheck
+      test: wget -qO - http://localhost:8080/health
+      interval: 5s
+      timeout: 1s
+      retries: 5
+    expose:
+      - 8080
   graph-gophers-service:
     healthcheck: *healthcheck
     build:
@@ -34,7 +44,7 @@ services:
     configs: [gateway]
     command: ["-config", "gateway"]
     environment:
-      - BRAMBLE_SERVICE_LIST=http://gqlgen-service:8080/query http://graph-gophers-service:8080/query http://slow-service:8080/query http://nodejs-service:8080/query
+      - BRAMBLE_SERVICE_LIST=http://gqlgen-service:8080/query http://gqlgen-multipart-file-upload-service:8080/query http://graph-gophers-service:8080/query http://slow-service:8080/query http://nodejs-service:8080/query
     ports:
       - 8082:8082
       - 8083:8083

docs/plugins.md

@@ -29,6 +29,19 @@ Add `CORS` headers to queries.
 }
 ```
 
+## Headers
+
+Allow headers to passthrough to downstream services.
+
+```json
+{
+  "name": "headers",
+  "config": {
+    "allowed-headers": ["X-Custom-Header"]
+  }
+}
+```
+
 ## JWT Auth
 
 The JWT auth plugin validates that the request contains a valid JWT and

examples/gqlgen-multipart-file-upload-service/.gitignore

@@ -0,0 +1,3 @@
+gqlgen-service
+generated.go
+models_gen.go

examples/gqlgen-multipart-file-upload-service/Dockerfile

@@ -0,0 +1,11 @@
+FROM golang:1.22-alpine3.19
+
+ENV CGO_ENABLED=0
+
+WORKDIR /go/src/app
+
+COPY . .
+
+RUN go generate .
+RUN go get
+CMD go run .

examples/gqlgen-multipart-file-upload-service/Makefile

@@ -0,0 +1,18 @@
+ARTIFACT=gqlgen-service
+DEF=gqlgen.yml schema.graphql
+GEN=models_gen.go generated.go
+
+build: $(ARTIFACT)
+
+.PHONY: clean
+clean:
+	rm -f $(ARTIFACT) $(GEN)
+
+.PHONY: generate
+generate: $(GEN)
+
+$(GEN): $(DEF)
+	go generate
+
+gqlgen-service: $(GEN) $(wildcard *.go)
+	go build