From ee1c11a8e77b47d9219bf1f80e675d0c650f7fd8 Mon Sep 17 00:00:00 2001
From: Reinier Schoof <reinier@skoef.nl>
Date: Mon, 23 Aug 2021 16:24:43 +0200
Subject: [PATCH] allow to set certain client-side capabilities

---
 client/auth.go        | 13 +++++++++++--
 client/client_test.go | 35 +++++++++++++++++++++++++++++++++++
 client/conn.go        | 13 +++++++++++++
 3 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/client/auth.go b/client/auth.go
index 01217f834..1a045be44 100644
--- a/client/auth.go
+++ b/client/auth.go
@@ -140,9 +140,18 @@ func (c *Conn) writeAuthHandshake() error {
 	if !authPluginAllowed(c.authPluginName) {
 		return fmt.Errorf("unknow auth plugin name '%s'", c.authPluginName)
 	}
-	// Adjust client capability flags based on server support
+
+	// Set default client capabilities that reflect the abilities of this library
 	capability := CLIENT_PROTOCOL_41 | CLIENT_SECURE_CONNECTION |
-		CLIENT_LONG_PASSWORD | CLIENT_TRANSACTIONS | CLIENT_PLUGIN_AUTH | c.capability&CLIENT_LONG_FLAG
+		CLIENT_LONG_PASSWORD | CLIENT_TRANSACTIONS | CLIENT_PLUGIN_AUTH
+	// Adjust client capability flags based on server support
+	capability |= c.capability & CLIENT_LONG_FLAG
+	// Adjust client capability flags on specific client requests
+	// Only flags that would make any sense setting and aren't handled elsewhere
+	// in the library are supported here
+	capability |= c.ccaps&CLIENT_FOUND_ROWS | c.ccaps&CLIENT_IGNORE_SPACE |
+		c.ccaps&CLIENT_MULTI_STATEMENTS | c.ccaps&CLIENT_MULTI_RESULTS |
+		c.ccaps&CLIENT_PS_MULTI_RESULTS | c.ccaps&CLIENT_CONNECT_ATTRS
 
 	// To enable TLS / SSL
 	if c.tlsConfig != nil {
diff --git a/client/client_test.go b/client/client_test.go
index 53d43c199..121051f1b 100644
--- a/client/client_test.go
+++ b/client/client_test.go
@@ -94,6 +94,41 @@ func (s *clientTestSuite) TestConn_Ping(c *C) {
 	c.Assert(err, IsNil)
 }
 
+func (s *clientTestSuite) TestConn_SetCapability(c *C) {
+	caps := []uint32{
+		mysql.CLIENT_LONG_PASSWORD,
+		mysql.CLIENT_FOUND_ROWS,
+		mysql.CLIENT_LONG_FLAG,
+		mysql.CLIENT_CONNECT_WITH_DB,
+		mysql.CLIENT_NO_SCHEMA,
+		mysql.CLIENT_COMPRESS,
+		mysql.CLIENT_ODBC,
+		mysql.CLIENT_LOCAL_FILES,
+		mysql.CLIENT_IGNORE_SPACE,
+		mysql.CLIENT_PROTOCOL_41,
+		mysql.CLIENT_INTERACTIVE,
+		mysql.CLIENT_SSL,
+		mysql.CLIENT_IGNORE_SIGPIPE,
+		mysql.CLIENT_TRANSACTIONS,
+		mysql.CLIENT_RESERVED,
+		mysql.CLIENT_SECURE_CONNECTION,
+		mysql.CLIENT_MULTI_STATEMENTS,
+		mysql.CLIENT_MULTI_RESULTS,
+		mysql.CLIENT_PS_MULTI_RESULTS,
+		mysql.CLIENT_PLUGIN_AUTH,
+		mysql.CLIENT_CONNECT_ATTRS,
+		mysql.CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA,
+	}
+
+	for _, cap := range caps {
+		c.Assert(s.c.ccaps&cap > 0, IsFalse)
+		s.c.SetCapability(cap)
+		c.Assert(s.c.ccaps&cap > 0, IsTrue)
+		s.c.UnsetCapability(cap)
+		c.Assert(s.c.ccaps&cap > 0, IsFalse)
+	}
+}
+
 // NOTE for MySQL 5.5 and 5.6, server side has to config SSL to pass the TLS test, otherwise, it will throw error that
 //      MySQL server does not support TLS required by the client. However, for MySQL 5.7 and above, auto generated certificates
 //      are used by default so that manual config is no longer necessary.
diff --git a/client/conn.go b/client/conn.go
index 1b3744466..02c10cffc 100644
--- a/client/conn.go
+++ b/client/conn.go
@@ -21,7 +21,10 @@ type Conn struct {
 	tlsConfig *tls.Config
 	proto     string
 
+	// server capabilities
 	capability uint32
+	// client-set capabilities only
+	ccaps uint32
 
 	status uint16
 
@@ -120,6 +123,16 @@ func (c *Conn) Ping() error {
 	return nil
 }
 
+// SetCapability enables the use of a specific capability
+func (c *Conn) SetCapability(cap uint32) {
+	c.ccaps |= cap
+}
+
+// UnsetCapability disables the use of a specific capability
+func (c *Conn) UnsetCapability(cap uint32) {
+	c.ccaps &= ^cap
+}
+
 // UseSSL: use default SSL
 // pass to options when connect
 func (c *Conn) UseSSL(insecureSkipVerify bool) {