add support for grpc metadata headers

add -H arrayString flag

Author: prnvbn

README.md

@@ -12,6 +12,17 @@
 
 ![Streaming call demo](demos/streaming.gif)
 
+### Request metadata
+
+Use `-H` or `--header` multiple times to send request metadata. Headers are
+included in both server reflection and RPC requests.
+
+```bash
+grpcexp --addr api.example.com:443 --tls \
+  -H "authorization: Bearer ${TOKEN}" \
+  -H "x-tenant-id: acme"
+```
+
 ## Installation
 
 ### Linux or MacOS

internal/cli/root.go

@@ -20,6 +20,7 @@ var (
 	port     int
 	addr     string
 	protoset string
+	headers  []string
 	useTLS   bool
 	timeout  time.Duration
 )
@@ -54,6 +55,7 @@ func run(cmd *cobra.Command, args []string) error {
 		Creds:     creds,
 		UserAgent: "grpcexp/" + strings.TrimSpace(version),
 		Protoset:  protoset,
+		Headers:   headers,
 	})
 	if err != nil {
 		return err
@@ -83,6 +85,7 @@ func init() {
 	rootCmd.Flags().IntVarP(&port, "port", "p", 50051, "grpc server port")
 	rootCmd.Flags().StringVarP(&addr, "addr", "a", "", "grpc server address")
 	rootCmd.Flags().StringVar(&protoset, "protoset", "", "path to protoset file (uses server reflection if not specified)")
+	rootCmd.Flags().StringArrayVarP(&headers, "header", "H", nil, "additional header in 'name: value' format (may be repeated)")
 	rootCmd.Flags().BoolVar(&useTLS, "tls", false, "use TLS to connect to the server")
 	rootCmd.Flags().DurationVar(&timeout, "timeout", 10*time.Second, "connection timeout")
 }

internal/cli/version.txt

@@ -1 +1 @@
-0.0.13
+0.0.14

internal/grpc/client.go

@@ -17,6 +17,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/reflect/protoreflect"
 )
 
@@ -25,6 +26,7 @@ type Config struct {
 	Creds     credentials.TransportCredentials
 	UserAgent string
 	Protoset  string
+	Headers   []string
 }
 
 type Client struct {
@@ -34,6 +36,10 @@ type Client struct {
 }
 
 func NewClient(ctx context.Context, config Config) (*Client, error) {
+	if err := validateHeaders(config.Headers); err != nil {
+		return nil, err
+	}
+
 	opts := []grpc.DialOption{
 		grpc.WithUserAgent(config.UserAgent),
 	}
@@ -50,6 +56,9 @@ func NewClient(ctx context.Context, config Config) (*Client, error) {
 		}
 	} else {
 		refCtx := context.Background()
+		if len(config.Headers) > 0 {
+			refCtx = metadata.NewOutgoingContext(refCtx, grpcurl.MetadataFromHeaders(config.Headers))
+		}
 		refClient := grpcreflect.NewClientAuto(refCtx, cc)
 		refClient.AllowMissingFileDescriptors()
 		source = grpcurl.DescriptorSourceFromServer(refCtx, refClient)
@@ -58,6 +67,16 @@ func NewClient(ctx context.Context, config Config) (*Client, error) {
 	return &Client{source: source, conn: cc, config: config}, nil
 }
 
+func validateHeaders(headers []string) error {
+	for _, header := range headers {
+		name, _, ok := strings.Cut(header, ":")
+		if !ok || strings.TrimSpace(name) == "" {
+			return fmt.Errorf("invalid header %q: expected 'name: value'", header)
+		}
+	}
+	return nil
+}
+
 func (c *Client) InvokeRPC(ctx context.Context, methodFullName string, request map[string]any) (string, error) {
 	jsonData, err := json.Marshal(request)
 	if err != nil {
@@ -78,7 +97,7 @@ func (c *Client) InvokeRPC(ctx context.Context, methodFullName string, request m
 		VerbosityLevel: 0,
 	}
 
-	err = grpcurl.InvokeRPC(ctx, c.source, c.conn, methodFullName, nil, handler, rf.Next)
+	err = grpcurl.InvokeRPC(ctx, c.source, c.conn, methodFullName, c.config.Headers, handler, rf.Next)
 	if err != nil {
 		return "", fmt.Errorf("RPC invocation failed: %w", err)
 	}
@@ -120,7 +139,7 @@ func (c *Client) InvokeStreaming(ctx context.Context, methodFullName string, req
 		return rf.Next(msg)
 	}
 
-	if err := grpcurl.InvokeRPC(ctx, c.source, c.conn, methodFullName, nil, handler, requestSupplier); err != nil {
+	if err := grpcurl.InvokeRPC(ctx, c.source, c.conn, methodFullName, c.config.Headers, handler, requestSupplier); err != nil {
 		events <- StreamEvent{Kind: StreamEventError, Err: fmt.Errorf("RPC invocation failed: %w", err)}
 		return err
 	}
@@ -152,6 +171,9 @@ func (c *Client) GRPCURLCommand(methodFullName string, request map[string]any) (
 	if c.config.UserAgent != "" {
 		args = append(args, "-user-agent", c.config.UserAgent)
 	}
+	for _, header := range c.config.Headers {
+		args = append(args, "-H", header)
+	}
 	args = append(args, "-d", string(jsonData), c.config.Target, methodFullName)
 
 	for i, arg := range args {

internal/grpc/client_test.go

@@ -6,13 +6,40 @@ import (
 	"google.golang.org/grpc/credentials/insecure"
 )
 
+func TestValidateHeaders(t *testing.T) {
+	tests := []struct {
+		name    string
+		headers []string
+		wantErr bool
+	}{
+		{name: "none"},
+		{name: "multiple", headers: []string{"authorization: Bearer token", "x-label: value:with:colons"}},
+		{name: "empty value", headers: []string{"x-debug:"}},
+		{name: "missing colon", headers: []string{"authorization"}, wantErr: true},
+		{name: "empty name", headers: []string{" : value"}, wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := validateHeaders(tt.headers)
+			if (err != nil) != tt.wantErr {
+				t.Fatalf("validateHeaders() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
 func TestGRPCURLCommand(t *testing.T) {
 	client := &Client{
 		config: Config{
 			Target:    "localhost:50051",
 			Creds:     insecure.NewCredentials(),
 			UserAgent: "grpcexp/test",
 			Protoset:  "api fixtures/echo.protoset",
+			Headers: []string{
+				"authorization: Bearer test-token",
+				"x-request-label: it's a test",
+			},
 		},
 	}
 
@@ -23,7 +50,7 @@ func TestGRPCURLCommand(t *testing.T) {
 		t.Fatalf("GRPCURLCommand returned error: %v", err)
 	}
 
-	want := `grpcurl -plaintext -protoset 'api fixtures/echo.protoset' -user-agent grpcexp/test -d '{"message":"it'"'"'s here"}' localhost:50051 echo.v1.EchoService.Echo`
+	want := `grpcurl -plaintext -protoset 'api fixtures/echo.protoset' -user-agent grpcexp/test -H 'authorization: Bearer test-token' -H 'x-request-label: it'"'"'s a test' -d '{"message":"it'"'"'s here"}' localhost:50051 echo.v1.EchoService.Echo`
 	if got != want {
 		t.Fatalf("GRPCURLCommand = %q, want %q", got, want)
 	}