op-service/client: Add http header option to BasicHTTPClient (#9601)

op-service/client/http.go

@@ -23,16 +23,40 @@ type HTTP interface {
 
 type BasicHTTPClient struct {
 	endpoint string
-	log      log.Logger
-	client   *http.Client
+	header   http.Header // optional header to use in every request
+
+	log    log.Logger
+	client *http.Client
 }
 
-func NewBasicHTTPClient(endpoint string, log log.Logger) *BasicHTTPClient {
-	return &BasicHTTPClient{
+func NewBasicHTTPClient(endpoint string, log log.Logger, opts ...BasicHTTPClientOption) *BasicHTTPClient {
+	c := &BasicHTTPClient{
 		endpoint: endpoint,
 		log:      log,
 		client:   &http.Client{Timeout: DefaultTimeoutSeconds * time.Second},
 	}
+
+	for _, opt := range opts {
+		opt.Apply(c)
+	}
+
+	return c
+}
+
+type BasicHTTPClientOption interface {
+	Apply(c *BasicHTTPClient)
+}
+
+type BasicHTTPClientOptionFn func(*BasicHTTPClient)
+
+func (fn BasicHTTPClientOptionFn) Apply(c *BasicHTTPClient) {
+	fn(c)
+}
+
+func WithHeader(h http.Header) BasicHTTPClientOption {
+	return BasicHTTPClientOptionFn(func(c *BasicHTTPClient) {
+		c.header = h
+	})
 }
 
 var ErrNoEndpoint = errors.New("no endpoint is configured")
@@ -54,10 +78,16 @@ func (cl *BasicHTTPClient) Get(ctx context.Context, p string, query url.Values,
 	if err != nil {
 		return nil, fmt.Errorf("%w: failed to construct request", err)
 	}
-	for k, values := range headers {
-		for _, v := range values {
-			req.Header.Add(k, v)
+	addHTTPHeaders(req.Header, cl.header, headers)
+	return cl.client.Do(req)
+}
+
+func addHTTPHeaders(header http.Header, hs ...http.Header) {
+	for _, h := range hs {
+		for key, values := range h {
+			for _, value := range values {
+				header.Add(key, value)
+			}
 		}
 	}
-	return cl.client.Do(req)
 }

op-service/client/http_test.go

+package client
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+
+	"golang.org/x/exp/slog"
+
+	"github.com/ethereum-optimism/optimism/op-service/testlog"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBasicHTTPClient(t *testing.T) {
+	called := make(chan *http.Request, 1)
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		called <- r
+	}))
+	defer ts.Close()
+
+	// generate deep clones
+	mkhdr := func() http.Header {
+		return http.Header{
+			"Foo":        []string{"bar", "baz"},
+			"Superchain": []string{"op"},
+		}
+	}
+	opt := WithHeader(mkhdr())
+	c := NewBasicHTTPClient(ts.URL, testlog.Logger(t, slog.LevelInfo), opt)
+
+	const ep = "/api/version"
+	query := url.Values{
+		"key": []string{"123"},
+	}
+	getheader := http.Header{
+		"Fruits":     []string{"apple"},
+		"Superchain": []string{"base"},
+	}
+	resp, err := c.Get(context.Background(), ep, query, getheader)
+	require.NoError(t, err)
+	defer resp.Body.Close()
+
+	require.Equal(t, http.StatusOK, resp.StatusCode)
+	req := <-called
+	require.Equal(t, ep, req.URL.Path)
+	require.Equal(t, query, req.URL.Query())
+	require.ElementsMatch(t, req.Header.Values("Foo"), mkhdr()["Foo"])
+	require.ElementsMatch(t, req.Header.Values("Fruits"), getheader["Fruits"])
+	require.ElementsMatch(t, req.Header.Values("Superchain"), []string{"op", "base"})
+}
+
+func TestAddHTTPHeaders(t *testing.T) {
+	for _, test := range []struct {
+		desc      string
+		expheader http.Header
+		headers   []http.Header
+	}{
+		{
+			desc:      "all-empty",
+			expheader: http.Header{},
+			headers:   nil,
+		},
+		{
+			desc:      "1-header-and-nils",
+			expheader: http.Header{"Foo": []string{"bar"}},
+			headers: []http.Header{
+				nil,
+				{"Foo": []string{"bar"}},
+				nil,
+			},
+		},
+		{
+			desc: "2-headers",
+			expheader: http.Header{
+				"Foo":   []string{"bar", "baz"},
+				"Super": []string{"chain"},
+				"Fruit": []string{"apple"},
+			},
+			headers: []http.Header{
+				{
+					"Foo":   []string{"bar"},
+					"Super": []string{"chain"},
+				},
+				{
+					"Foo":   []string{"baz"},
+					"Fruit": []string{"apple"},
+				},
+			},
+		},
+	} {
+		t.Run(test.desc, func(t *testing.T) {
+			h := make(http.Header)
+			addHTTPHeaders(h, test.headers...)
+			require.Equal(t, test.expheader, h)
+		})
+	}
+}