From 573396108a76cd2f7f6c1e3c651304a3f3e52fee Mon Sep 17 00:00:00 2001
From: Kristin Laemmert <mildwonkey@users.noreply.github.com>
Date: Wed, 24 Mar 2021 13:22:54 -0400
Subject: [PATCH 1/3] add ProtocolVersion to ReattachConfig

A client connecting to a plugin process needs to know the resolved ProtocolVersion, so this PR adds that information to the returned reattach config. Prior to this, client.NegotiatedVersion() always returned 0.
---
 client.go | 8 +++++---
 server.go | 9 +++++----
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/client.go b/client.go
index 780a3121..29a79222 100644
--- a/client.go
+++ b/client.go
@@ -209,9 +209,10 @@ type ClientConfig struct {
 // already-running plugin process. You can retrieve this information by
 // calling ReattachConfig on Client.
 type ReattachConfig struct {
-	Protocol Protocol
-	Addr     net.Addr
-	Pid      int
+	Protocol        Protocol
+	ProtocolVersion int
+	Addr            net.Addr
+	Pid             int
 
 	// Test is set to true if this is reattaching to to a plugin in "test mode"
 	// (see ServeConfig.Test). In this mode, client.Kill will NOT kill the
@@ -838,6 +839,7 @@ func (c *Client) reattach() (net.Addr, error) {
 		// Default the protocol to net/rpc for backwards compatibility
 		c.protocol = ProtocolNetRPC
 	}
+	c.negotiatedVersion = c.config.Reattach.ProtocolVersion
 
 	// If we're in test mode, we do NOT set the process. This avoids the
 	// process being killed (the only purpose we have for c.process), since
diff --git a/server.go b/server.go
index 80f0ac39..7a58cc39 100644
--- a/server.go
+++ b/server.go
@@ -415,10 +415,11 @@ func Serve(opts *ServeConfig) {
 		// quite ready if they connect immediately but the client should
 		// retry a few times.
 		ch <- &ReattachConfig{
-			Protocol: protoType,
-			Addr:     listener.Addr(),
-			Pid:      os.Getpid(),
-			Test:     true,
+			Protocol:        protoType,
+			ProtocolVersion: protoVersion,
+			Addr:            listener.Addr(),
+			Pid:             os.Getpid(),
+			Test:            true,
 		}
 	}
 

From 096aa0ea2fb379207e74ae7669d38a17ac8fe272 Mon Sep 17 00:00:00 2001
From: Kristin Laemmert <mildwonkey@users.noreply.github.com>
Date: Wed, 31 Mar 2021 09:19:34 -0400
Subject: [PATCH 2/3] only set c.negotiatedVersion if we are in reattach test
 mode to reduce changes for existing callers

---
 client.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/client.go b/client.go
index 29a79222..6b42975b 100644
--- a/client.go
+++ b/client.go
@@ -839,7 +839,10 @@ func (c *Client) reattach() (net.Addr, error) {
 		// Default the protocol to net/rpc for backwards compatibility
 		c.protocol = ProtocolNetRPC
 	}
-	c.negotiatedVersion = c.config.Reattach.ProtocolVersion
+
+	if c.config.Reattach.Test {
+		c.negotiatedVersion = c.config.Reattach.ProtocolVersion
+	}
 
 	// If we're in test mode, we do NOT set the process. This avoids the
 	// process being killed (the only purpose we have for c.process), since

From bc2dbfce56b47f933dcc9b5fa38b5175cebe5ded Mon Sep 17 00:00:00 2001
From: Kristin Laemmert <mildwonkey@users.noreply.github.com>
Date: Wed, 31 Mar 2021 10:44:05 -0400
Subject: [PATCH 3/3] Add a test for correct protocol version in reattach
 config

---
 server_test.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/server_test.go b/server_test.go
index 099cfc76..5fec4502 100644
--- a/server_test.go
+++ b/server_test.go
@@ -42,6 +42,11 @@ func TestServer_testMode(t *testing.T) {
 		t.Fatal("config should not be nil")
 	}
 
+	// Check that the reattach config includes the negotiated protocol version
+	if config.ProtocolVersion != int(testHandshake.ProtocolVersion) {
+		t.Fatalf("wrong protocol version in reattach config. got %d, expected %d", config.ProtocolVersion, testHandshake.ProtocolVersion)
+	}
+
 	// Connect!
 	c := NewClient(&ClientConfig{
 		Cmd:              nil,