feat(httpclient): support appending the same header multiple times

See #829

backend/http_settings.go

@@ -3,6 +3,7 @@ package backend
 import (
 	"encoding/json"
 	"fmt"
+	"net/http"
 	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend/httpclient"
@@ -16,7 +17,7 @@ type HTTPSettings struct {
 	BasicAuthEnabled  bool
 	BasicAuthUser     string
 	BasicAuthPassword string
-	Headers           map[string]string
+	Header            http.Header
 
 	Timeout               time.Duration
 	DialTimeout           time.Duration
@@ -52,7 +53,7 @@ type HTTPSettings struct {
 // HTTPClientOptions creates and returns httpclient.Options.
 func (s *HTTPSettings) HTTPClientOptions() httpclient.Options {
 	opts := httpclient.Options{
-		Headers:       s.Headers,
+		Header:        s.Header,
 		Labels:        map[string]string{},
 		CustomOptions: map[string]interface{}{},
 	}
@@ -104,7 +105,7 @@ func (s *HTTPSettings) HTTPClientOptions() httpclient.Options {
 //gocyclo:ignore
 func parseHTTPSettings(jsonData json.RawMessage, secureJSONData map[string]string) (*HTTPSettings, error) {
 	s := &HTTPSettings{
-		Headers: map[string]string{},
+		Header: http.Header{},
 	}
 
 	var dat map[string]interface{}
@@ -273,7 +274,7 @@ func parseHTTPSettings(jsonData json.RawMessage, secureJSONData map[string]strin
 
 		if key, exists := dat[headerNameSuffix]; exists {
 			if value, exists := secureJSONData[headerValueSuffix]; exists {
-				s.Headers[key.(string)] = value
+				s.Header.Add(key.(string), value)
 			}
 		} else {
 			// No (more) header values are available

backend/http_settings_test.go

@@ -2,6 +2,7 @@ package backend
 
 import (
 	"encoding/json"
+	"net/http"
 	"testing"
 	"time"
 
@@ -44,7 +45,8 @@ func TestParseHTTPSettings(t *testing.T) {
 			"sigV4ExternalId": "ext123",
 			"sigV4Profile": "ghi",
 			"httpHeaderName1": "X-HeaderOne",
-			"httpHeaderName2": "X-HeaderTwo"
+			"httpHeaderName2": "X-HeaderTwo",
+			"httpHeaderName3": "X-HeaderTwo"
 		}`
 		secureData := map[string]string{
 			"basicAuthPassword": "pwd",
@@ -55,6 +57,7 @@ func TestParseHTTPSettings(t *testing.T) {
 			"sigV4SecretKey":    "sigV4SecretKey5",
 			"httpHeaderValue1":  "SecretOne",
 			"httpHeaderValue2":  "SecretTwo",
+			"httpHeaderValue3":  "SecretThree",
 		}
 		var jsonMap map[string]interface{}
 		err := json.Unmarshal([]byte(jsonStr), &jsonMap)
@@ -68,9 +71,9 @@ func TestParseHTTPSettings(t *testing.T) {
 			BasicAuthEnabled:  true,
 			BasicAuthUser:     "user",
 			BasicAuthPassword: "pwd",
-			Headers: map[string]string{
-				"X-HeaderOne": "SecretOne",
-				"X-HeaderTwo": "SecretTwo",
+			Header: http.Header{
+				"X-Headerone": {"SecretOne"},
+				"X-Headertwo": {"SecretTwo", "SecretThree"},
 			},
 			Timeout:               10 * time.Second,
 			DialTimeout:           10 * time.Second,
@@ -108,9 +111,9 @@ func TestParseHTTPSettings(t *testing.T) {
 					User:     "user",
 					Password: "pwd",
 				},
-				Headers: map[string]string{
-					"X-HeaderOne": "SecretOne",
-					"X-HeaderTwo": "SecretTwo",
+				Header: http.Header{
+					"X-Headerone": {"SecretOne"},
+					"X-Headertwo": {"SecretTwo", "SecretThree"},
 				},
 				Timeouts: &httpclient.TimeoutOptions{
 					Timeout:               10 * time.Second,

backend/httpclient/custom_headers_middleware.go

@@ -12,17 +12,19 @@ const CustomHeadersMiddlewareName = "CustomHeaders"
 // If opts.Headers is empty, next will be returned.
 func CustomHeadersMiddleware() Middleware {
 	return NamedMiddlewareFunc(CustomHeadersMiddlewareName, func(opts Options, next http.RoundTripper) http.RoundTripper {
-		if len(opts.Headers) == 0 {
+		if len(opts.Header) == 0 {
 			return next
 		}
 
 		return RoundTripperFunc(func(req *http.Request) (*http.Response, error) {
-			for key, value := range opts.Headers {
+			for key, values := range opts.Header {
 				// According to https://pkg.go.dev/net/http#Request.Header, Host is a special case
 				if http.CanonicalHeaderKey(key) == "Host" {
-					req.Host = value
+					req.Host = values[0]
 				} else {
-					req.Header.Set(key, value)
+					for _, value := range values {
+						req.Header.Add(key, value)
+					}
 				}
 			}
 

backend/httpclient/custom_headers_middleware_test.go

@@ -34,10 +34,10 @@ func TestCustomHeadersMiddleware(t *testing.T) {
 		ctx := &testContext{}
 		finalRoundTripper := ctx.createRoundTripper("final")
 		customHeaders := CustomHeadersMiddleware()
-		rt := customHeaders.CreateMiddleware(Options{Headers: map[string]string{
-			"X-HeaderOne":   "ValueOne",
-			"X-HeaderTwo":   "ValueTwo",
-			"X-HeaderThree": "ValueThree",
+		rt := customHeaders.CreateMiddleware(Options{Header: http.Header{
+			"X-Headerone":   {"ValueOne"},
+			"X-Headertwo":   {"ValueTwo"},
+			"X-Headerthree": {"ValueThree", "ValueThreeAgain"},
 		}}, finalRoundTripper)
 		require.NotNil(t, rt)
 		middlewareName, ok := customHeaders.(MiddlewareName)
@@ -55,9 +55,9 @@ func TestCustomHeadersMiddleware(t *testing.T) {
 		require.Len(t, ctx.callChain, 1)
 		require.ElementsMatch(t, []string{"final"}, ctx.callChain)
 
-		require.Equal(t, "ValueOne", req.Header.Get("X-HeaderOne"))
-		require.Equal(t, "ValueTwo", req.Header.Get("X-HeaderTwo"))
-		require.Equal(t, "ValueThree", req.Header.Get("X-HeaderThree"))
+		require.Equal(t, []string{"ValueOne"}, req.Header.Values("X-Headerone"))
+		require.Equal(t, []string{"ValueTwo"}, req.Header.Values("X-Headertwo"))
+		require.Equal(t, []string{"ValueThree", "ValueThreeAgain"}, req.Header.Values("X-Headerthree"))
 	})
 
 	t.Run("With custom Host header set should apply Host to the request", func(t *testing.T) {

backend/httpclient/options.go

@@ -38,7 +38,7 @@ type Options struct {
 	ProxyOptions *proxy.Options
 
 	// Headers custom headers.
-	Headers map[string]string
+	Header http.Header
 
 	// CustomOptions allows custom options to be provided.
 	CustomOptions map[string]interface{}

experimental/authclient/authclient_test.go

@@ -31,7 +31,7 @@ func TestNew(t *testing.T) {
 		t.Run("client credentials", func(t *testing.T) {
 			t.Run("valid client credentials", func(t *testing.T) {
 				hc, err := authclient.New(httpclient.Options{
-					Headers: map[string]string{"h1": "v1"},
+					Header: http.Header{"H1": {"v1"}},
 				}, authclient.AuthOptions{
 					AuthMethod: authclient.AuthMethodOAuth2,
 					OAuth2Options: &authclient.OAuth2Options{
@@ -54,7 +54,7 @@ func TestNew(t *testing.T) {
 			})
 			t.Run("valid client credentials with basic auth settings", func(t *testing.T) {
 				hc, err := authclient.New(httpclient.Options{
-					Headers:   map[string]string{"h1": "v1"},
+					Header:    http.Header{"H1": {"v1"}},
 					BasicAuth: &httpclient.BasicAuthOptions{User: "userFoo", Password: "pwdBar"},
 				}, authclient.AuthOptions{
 					AuthMethod: authclient.AuthMethodOAuth2,
@@ -81,7 +81,7 @@ func TestNew(t *testing.T) {
 			t.Run("invalid private key", func(t *testing.T) {
 				privateKey := generateKey(t, true)
 				hc, err := authclient.New(httpclient.Options{
-					Headers: map[string]string{"h1": "v1"},
+					Header: http.Header{"H1": {"v1"}},
 				}, authclient.AuthOptions{
 					AuthMethod: authclient.AuthMethodOAuth2,
 					OAuth2Options: &authclient.OAuth2Options{
@@ -103,7 +103,7 @@ func TestNew(t *testing.T) {
 			t.Run("valid private key", func(t *testing.T) {
 				privateKey := generateKey(t, false)
 				hc, err := authclient.New(httpclient.Options{
-					Headers: map[string]string{"h1": "v1"},
+					Header: http.Header{"H1": {"v1"}},
 				}, authclient.AuthOptions{
 					AuthMethod: authclient.AuthMethodOAuth2,
 					OAuth2Options: &authclient.OAuth2Options{
@@ -134,7 +134,7 @@ func getOAuthServer(t *testing.T) *httptest.Server {
 	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		oAuth2TokenValue := "foo"
 		t.Run("ensure custom headers propagated correctly", func(t *testing.T) {
-			require.Equal(t, "v1", r.Header.Get("h1"))
+			require.Equal(t, "v1", r.Header.Get("H1"))
 		})
 		if r.URL.String() == handlerToken {
 			w.Header().Set("Content-Type", "application/json")