THRIFT-4914: Make TClient.Call to return the response meta

Client: go

Make a breaking change so that TClient.Call returns the response
meta, currently only contains headers but could be expanded in the
future, and make a compiler change to compiler generated clients to take
advantage of that and provide access to response metadata to users.

5 files changed, 27 insertions, 27 deletions

diff --git a/lib/go/thrift/client.go b/lib/go/thrift/client.go
index 1c5705d55..ea2c01fda 100644
--- a/lib/go/thrift/client.go
+++ b/lib/go/thrift/client.go
@@ -5,8 +5,15 @@ import (
 	"fmt"
 )
 
+// ResponseMeta represents the metadata attached to the response.
+type ResponseMeta struct {
+	// The headers in the response, if any.
+	// If the underlying transport/protocol is not THeader, this will always be nil.
+	Headers THeaderMap
+}
+
 type TClient interface {
-	Call(ctx context.Context, method string, args, result TStruct) error
+	Call(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error)
 }
 
 type TStandardClient struct {
@@ -78,18 +85,25 @@ func (p *TStandardClient) Recv(ctx context.Context, iprot TProtocol, seqId int32
 	return iprot.ReadMessageEnd(ctx)
 }
 
-func (p *TStandardClient) Call(ctx context.Context, method string, args, result TStruct) error {
+func (p *TStandardClient) Call(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error) {
 	p.seqId++
 	seqId := p.seqId
 
 	if err := p.Send(ctx, p.oprot, seqId, method, args); err != nil {
-		return err
+		return ResponseMeta{}, err
 	}
 
 	// method is oneway
 	if result == nil {
-		return nil
+		return ResponseMeta{}, nil
 	}
 
-	return p.Recv(ctx, p.iprot, seqId, method, result)
+	err := p.Recv(ctx, p.iprot, seqId, method, result)
+	var headers THeaderMap
+	if hp, ok := p.iprot.(*THeaderProtocol); ok {
+		headers = hp.transport.readHeaders
+	}
+	return ResponseMeta{
+		Headers: headers,
+	}, err
 }
diff --git a/lib/go/thrift/example_client_middleware_test.go b/lib/go/thrift/example_client_middleware_test.go
index 8a29083c0..a68cdbc34 100644
--- a/lib/go/thrift/example_client_middleware_test.go
+++ b/lib/go/thrift/example_client_middleware_test.go
@@ -45,16 +45,16 @@ func NewMyServiceClient(_ TClient) MyService {
 
 func simpleClientLoggingMiddleware(next TClient) TClient {
 	return WrappedTClient{
-		Wrapped: func(ctx context.Context, method string, args, result TStruct) error {
+		Wrapped: func(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error) {
 			log.Printf("Before: %q", method)
 			log.Printf("Args: %#v", args)
-			err := next.Call(ctx, method, args, result)
+			headers, err := next.Call(ctx, method, args, result)
 			log.Printf("After: %q", method)
 			log.Printf("Result: %#v", result)
 			if err != nil {
 				log.Printf("Error: %v", err)
 			}
-			return err
+			return headers, err
 		},
 	}
 }
diff --git a/lib/go/thrift/header_protocol.go b/lib/go/thrift/header_protocol.go
index 35e045805..878041f8d 100644
--- a/lib/go/thrift/header_protocol.go
+++ b/lib/go/thrift/header_protocol.go
@@ -345,20 +345,6 @@ func (p *THeaderProtocol) SetTConfiguration(cfg *TConfiguration) {
 	p.cfg = cfg
 }
 
-// GetResponseHeadersFromClient is a helper function to get the read THeaderMap
-// from the last response received from the given client.
-//
-// If the last response was not sent over THeader protocol,
-// a nil map will be returned.
-func GetResponseHeadersFromClient(c TClient) THeaderMap {
-	if sc, ok := c.(*TStandardClient); ok {
-		if hp, ok := sc.iprot.(*THeaderProtocol); ok {
-			return hp.transport.readHeaders
-		}
-	}
-	return nil
-}
-
 var (
 	_ TConfigurationSetter = (*tHeaderProtocolFactory)(nil)
 	_ TConfigurationSetter = (*THeaderProtocol)(nil)
diff --git a/lib/go/thrift/middleware.go b/lib/go/thrift/middleware.go
index b575e16c4..8a788df02 100644
--- a/lib/go/thrift/middleware.go
+++ b/lib/go/thrift/middleware.go
@@ -78,11 +78,11 @@ type ClientMiddleware func(TClient) TClient
 //
 // This is provided to aid in developing ClientMiddleware.
 type WrappedTClient struct {
-	Wrapped func(ctx context.Context, method string, args, result TStruct) error
+	Wrapped func(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error)
 }
 
 // Call implements the TClient interface by calling and returning c.Wrapped.
-func (c WrappedTClient) Call(ctx context.Context, method string, args, result TStruct) error {
+func (c WrappedTClient) Call(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error) {
 	return c.Wrapped(ctx, method, args, result)
 }
 
diff --git a/lib/go/thrift/middleware_test.go b/lib/go/thrift/middleware_test.go
index 2a4d1f957..6c4058fe1 100644
--- a/lib/go/thrift/middleware_test.go
+++ b/lib/go/thrift/middleware_test.go
@@ -54,7 +54,7 @@ func testProcessorMiddleware(c *counter) ProcessorMiddleware {
 func testClientMiddleware(c *counter) ClientMiddleware {
 	return func(next TClient) TClient {
 		return WrappedTClient{
-			Wrapped: func(ctx context.Context, method string, args, result TStruct) error {
+			Wrapped: func(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error) {
 				c.incr()
 				return next.Call(ctx, method, args, result)
 			},
@@ -122,8 +122,8 @@ func TestWrapTMultiplexedProcessor(t *testing.T) {
 
 func TestWrapClient(t *testing.T) {
 	client := WrappedTClient{
-		Wrapped: func(ctx context.Context, method string, args, result TStruct) error {
-			return nil
+		Wrapped: func(ctx context.Context, method string, args, result TStruct) (ResponseMeta, error) {
+			return ResponseMeta{}, nil
 		},
 	}
 	c := newCounter(t)