client: define dialOptions as interfaces instead of functions (#2230)

clientconn.go

@@ -140,7 +140,7 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 	cc.ctx, cc.cancel = context.WithCancel(context.Background())
 
 	for _, opt := range opts {
-		opt(&cc.dopts)
+		opt.apply(&cc.dopts)
 	}
 
 	if channelz.IsOn() {

dialoptions.go

@@ -62,14 +62,40 @@ type dialOptions struct {
 }
 
 // DialOption configures how we set up the connection.
-type DialOption func(*dialOptions)
+type DialOption interface {
+	apply(*dialOptions)
+}
+
+// EmptyDialOption does not alter the dial configuration. It can be embedded in
+// another structure to build custom dial options.
+//
+// This API is EXPERIMENTAL.
+type EmptyDialOption struct{}
+
+func (EmptyDialOption) apply(*dialOptions) {}
+
+// funcDialOption wraps a function that modifies dialOptions into an
+// implementation of the DialOption interface.
+type funcDialOption struct {
+	f func(*dialOptions)
+}
+
+func (fdo *funcDialOption) apply(do *dialOptions) {
+	fdo.f(do)
+}
+
+func newFuncDialOption(f func(*dialOptions)) *funcDialOption {
+	return &funcDialOption{
+		f: f,
+	}
+}
 
 // WithWaitForHandshake blocks until the initial settings frame is received from
 // the server before assigning RPCs to the connection. Experimental API.
 func WithWaitForHandshake() DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.waitForHandshake = true
-	}
+	})
 }
 
 // WithWriteBufferSize determines how much data can be batched before doing a
@@ -80,9 +106,9 @@ func WithWaitForHandshake() DialOption {
 // Zero will disable the write buffer such that each write will be on underlying
 // connection. Note: A Send call may not directly translate to a write.
 func WithWriteBufferSize(s int) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.WriteBufferSize = s
-	}
+	})
 }
 
 // WithReadBufferSize lets you set the size of read buffer, this determines how
@@ -91,27 +117,27 @@ func WithWriteBufferSize(s int) DialOption {
 // The default value for this buffer is 32KB. Zero will disable read buffer for
 // a connection so data framer can access the underlying conn directly.
 func WithReadBufferSize(s int) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.ReadBufferSize = s
-	}
+	})
 }
 
 // WithInitialWindowSize returns a DialOption which sets the value for initial
 // window size on a stream. The lower bound for window size is 64K and any value
 // smaller than that will be ignored.
 func WithInitialWindowSize(s int32) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.InitialWindowSize = s
-	}
+	})
 }
 
 // WithInitialConnWindowSize returns a DialOption which sets the value for
 // initial window size on a connection. The lower bound for window size is 64K
 // and any value smaller than that will be ignored.
 func WithInitialConnWindowSize(s int32) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.InitialConnWindowSize = s
-	}
+	})
 }
 
 // WithMaxMsgSize returns a DialOption which sets the maximum message size the
@@ -125,9 +151,9 @@ func WithMaxMsgSize(s int) DialOption {
 // WithDefaultCallOptions returns a DialOption which sets the default
 // CallOptions for calls over the connection.
 func WithDefaultCallOptions(cos ...CallOption) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.callOptions = append(o.callOptions, cos...)
-	}
+	})
 }
 
 // WithCodec returns a DialOption which sets a codec for message marshaling and
@@ -144,9 +170,9 @@ func WithCodec(c Codec) DialOption {
 //
 // Deprecated: use UseCompressor instead.
 func WithCompressor(cp Compressor) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.cp = cp
-	}
+	})
 }
 
 // WithDecompressor returns a DialOption which sets a Decompressor to use for
@@ -159,9 +185,9 @@ func WithCompressor(cp Compressor) DialOption {
 //
 // Deprecated: use encoding.RegisterCompressor instead.
 func WithDecompressor(dc Decompressor) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.dc = dc
-	}
+	})
 }
 
 // WithBalancer returns a DialOption which sets a load balancer with the v1 API.
@@ -170,11 +196,11 @@ func WithDecompressor(dc Decompressor) DialOption {
 // Deprecated: use the new balancer APIs in balancer package and
 // WithBalancerName.
 func WithBalancer(b Balancer) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.balancerBuilder = &balancerWrapperBuilder{
 			b: b,
 		}
-	}
+	})
 }
 
 // WithBalancerName sets the balancer that the ClientConn will be initialized
@@ -190,16 +216,16 @@ func WithBalancerName(balancerName string) DialOption {
 	if builder == nil {
 		panic(fmt.Sprintf("grpc.WithBalancerName: no balancer is registered for name %v", balancerName))
 	}
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.balancerBuilder = builder
-	}
+	})
 }
 
 // withResolverBuilder is only for grpclb.
 func withResolverBuilder(b resolver.Builder) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.resolverBuilder = b
-	}
+	})
 }
 
 // WithServiceConfig returns a DialOption which has a channel to read the
@@ -209,9 +235,9 @@ func withResolverBuilder(b resolver.Builder) DialOption {
 // specified here.
 // https://github.com/grpc/grpc/blob/master/doc/service_config.md
 func WithServiceConfig(c <-chan ServiceConfig) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.scChan = c
-	}
+	})
 }
 
 // WithBackoffMaxDelay configures the dialer to use the provided maximum delay
@@ -236,43 +262,43 @@ func WithBackoffConfig(b BackoffConfig) DialOption {
 //
 // This can be exported if arbitrary backoff strategies are allowed by gRPC.
 func withBackoff(bs backoff.Strategy) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.bs = bs
-	}
+	})
 }
 
 // WithBlock returns a DialOption which makes caller of Dial blocks until the
 // underlying connection is up. Without this, Dial returns immediately and
 // connecting the server happens in background.
 func WithBlock() DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.block = true
-	}
+	})
 }
 
 // WithInsecure returns a DialOption which disables transport security for this
 // ClientConn. Note that transport security is required unless WithInsecure is
 // set.
 func WithInsecure() DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.insecure = true
-	}
+	})
 }
 
 // WithTransportCredentials returns a DialOption which configures a connection
 // level security credentials (e.g., TLS/SSL).
 func WithTransportCredentials(creds credentials.TransportCredentials) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.TransportCredentials = creds
-	}
+	})
 }
 
 // WithPerRPCCredentials returns a DialOption which sets credentials and places
 // auth state on each outbound RPC.
 func WithPerRPCCredentials(creds credentials.PerRPCCredentials) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.PerRPCCredentials = append(o.copts.PerRPCCredentials, creds)
-	}
+	})
 }
 
 // WithTimeout returns a DialOption that configures a timeout for dialing a
@@ -280,15 +306,15 @@ func WithPerRPCCredentials(creds credentials.PerRPCCredentials) DialOption {
 //
 // Deprecated: use DialContext and context.WithTimeout instead.
 func WithTimeout(d time.Duration) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.timeout = d
-	}
+	})
 }
 
 func withContextDialer(f func(context.Context, string) (net.Conn, error)) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.Dialer = f
-	}
+	})
 }
 
 func init() {
@@ -313,9 +339,9 @@ func WithDialer(f func(string, time.Duration) (net.Conn, error)) DialOption {
 // WithStatsHandler returns a DialOption that specifies the stats handler for
 // all the RPCs and underlying network connections in this ClientConn.
 func WithStatsHandler(h stats.Handler) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.StatsHandler = h
-	}
+	})
 }
 
 // FailOnNonTempDialError returns a DialOption that specifies if gRPC fails on
@@ -325,68 +351,68 @@ func WithStatsHandler(h stats.Handler) DialOption {
 //
 // This is an EXPERIMENTAL API.
 func FailOnNonTempDialError(f bool) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.FailOnNonTempDialError = f
-	}
+	})
 }
 
 // WithUserAgent returns a DialOption that specifies a user agent string for all
 // the RPCs.
 func WithUserAgent(s string) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.UserAgent = s
-	}
+	})
 }
 
 // WithKeepaliveParams returns a DialOption that specifies keepalive parameters
 // for the client transport.
 func WithKeepaliveParams(kp keepalive.ClientParameters) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.KeepaliveParams = kp
-	}
+	})
 }
 
 // WithUnaryInterceptor returns a DialOption that specifies the interceptor for
 // unary RPCs.
 func WithUnaryInterceptor(f UnaryClientInterceptor) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.unaryInt = f
-	}
+	})
 }
 
 // WithStreamInterceptor returns a DialOption that specifies the interceptor for
 // streaming RPCs.
 func WithStreamInterceptor(f StreamClientInterceptor) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.streamInt = f
-	}
+	})
 }
 
 // WithAuthority returns a DialOption that specifies the value to be used as the
 // :authority pseudo-header. This value only works with WithInsecure and has no
 // effect if TransportCredentials are present.
 func WithAuthority(a string) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.authority = a
-	}
+	})
 }
 
 // WithChannelzParentID returns a DialOption that specifies the channelz ID of
 // current ClientConn's parent. This function is used in nested channel creation
 // (e.g. grpclb dial).
 func WithChannelzParentID(id int64) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.channelzParentID = id
-	}
+	})
 }
 
 // WithDisableServiceConfig returns a DialOption that causes grpc to ignore any
 // service config provided by the resolver and provides a hint to the resolver
 // to not fetch service configs.
 func WithDisableServiceConfig() DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.disableServiceConfig = true
-	}
+	})
 }
 
 // WithDisableRetry returns a DialOption that disables retries, even if the
@@ -400,17 +426,17 @@ func WithDisableServiceConfig() DialOption {
 //
 // This API is EXPERIMENTAL.
 func WithDisableRetry() DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.disableRetry = true
-	}
+	})
 }
 
 // WithMaxHeaderListSize returns a DialOption that specifies the maximum
 // (uncompressed) size of header list that the client is prepared to accept.
 func WithMaxHeaderListSize(s uint32) DialOption {
-	return func(o *dialOptions) {
+	return newFuncDialOption(func(o *dialOptions) {
 		o.copts.MaxHeaderListSize = &s
-	}
+	})
 }
 
 func defaultDialOptions() dialOptions {