allow unknown collation name (go-sql-driver#1604)

Fix go-sql-driver#1603

collations.go

@@ -8,7 +8,7 @@
 
 package mysql
 
-const defaultCollation = "utf8mb4_general_ci"
+const defaultCollationID = 45 // utf8mb4_general_ci
 const binaryCollationID = 63
 
 // A list of available collations mapped to the internal ID.

connection.go

@@ -67,45 +67,20 @@ func (mc *mysqlConn) handleParams() (err error) {
 	var cmdSet strings.Builder
 
 	for param, val := range mc.cfg.Params {
-		switch param {
-		// Charset: character_set_connection, character_set_client, character_set_results
-		case "charset":
-			charsets := strings.Split(val, ",")
-			for _, cs := range charsets {
-				// ignore errors here - a charset may not exist
-				if mc.cfg.Collation != "" {
-					err = mc.exec("SET NAMES " + cs + " COLLATE " + mc.cfg.Collation)
-				} else {
-					err = mc.exec("SET NAMES " + cs)
-				}
-				if err == nil {
-					break
-				}
-			}
-			if err != nil {
-				return
-			}
-
-		// Other system vars accumulated in a single SET command
-		default:
-			if cmdSet.Len() == 0 {
-				// Heuristic: 29 chars for each other key=value to reduce reallocations
-				cmdSet.Grow(4 + len(param) + 3 + len(val) + 30*(len(mc.cfg.Params)-1))
-				cmdSet.WriteString("SET ")
-			} else {
-				cmdSet.WriteString(", ")
-			}
-			cmdSet.WriteString(param)
-			cmdSet.WriteString(" = ")
-			cmdSet.WriteString(val)
+		if cmdSet.Len() == 0 {
+			// Heuristic: 29 chars for each other key=value to reduce reallocations
+			cmdSet.Grow(4 + len(param) + 3 + len(val) + 30*(len(mc.cfg.Params)-1))
+			cmdSet.WriteString("SET ")
+		} else {
+			cmdSet.WriteString(", ")
 		}
+		cmdSet.WriteString(param)
+		cmdSet.WriteString(" = ")
+		cmdSet.WriteString(val)
 	}
 
 	if cmdSet.Len() > 0 {
 		err = mc.exec(cmdSet.String())
-		if err != nil {
-			return
-		}
 	}
 
 	return

connector.go

@@ -180,6 +180,25 @@ func (c *connector) Connect(ctx context.Context) (driver.Conn, error) {
 		mc.maxWriteSize = mc.maxAllowedPacket
 	}
 
+	// Charset: character_set_connection, character_set_client, character_set_results
+	if len(mc.cfg.charsets) > 0 {
+		for _, cs := range mc.cfg.charsets {
+			// ignore errors here - a charset may not exist
+			if mc.cfg.Collation != "" {
+				err = mc.exec("SET NAMES " + cs + " COLLATE " + mc.cfg.Collation)
+			} else {
+				err = mc.exec("SET NAMES " + cs)
+			}
+			if err == nil {
+				break
+			}
+		}
+		if err != nil {
+			mc.Close()
+			return nil, err
+		}
+	}
+
 	// Handle DSN Params
 	err = mc.handleParams()
 	if err != nil {

dsn.go

@@ -44,7 +44,8 @@ type Config struct {
 	DBName               string            // Database name
 	Params               map[string]string // Connection parameters
 	ConnectionAttributes string            // Connection Attributes, comma-delimited string of user-defined "key:value" pairs
-	Collation            string            // Connection collation
+	charsets             []string          // Connection charset. When set, this will be set in SET NAMES <charset> query
+	Collation            string            // Connection collation. When set, this will be set in SET NAMES <charset> COLLATE <collation> query
 	Loc                  *time.Location    // Location for time.Time values
 	MaxAllowedPacket     int               // Max packet size allowed
 	ServerPubKey         string            // Server public key name
@@ -282,6 +283,10 @@ func (cfg *Config) FormatDSN() string {
 		writeDSNParam(&buf, &hasParam, "clientFoundRows", "true")
 	}
 
+	if charsets := cfg.charsets; len(charsets) > 0 {
+		writeDSNParam(&buf, &hasParam, "charset", strings.Join(charsets, ","))
+	}
+
 	if col := cfg.Collation; col != "" {
 		writeDSNParam(&buf, &hasParam, "collation", col)
 	}
@@ -501,6 +506,10 @@ func parseDSNParams(cfg *Config, params string) (err error) {
 				return errors.New("invalid bool value: " + value)
 			}
 
+		// charset
+		case "charset":
+			cfg.charsets = strings.Split(value, ",")
+
 		// Collation
 		case "collation":
 			cfg.Collation = value

dsn_test.go

@@ -31,13 +31,13 @@ var testDSNs = []struct {
 	&Config{User: "username", Passwd: "password", Net: "protocol", Addr: "address", DBName: "dbname", Params: map[string]string{"param": "value"}, Loc: time.UTC, MaxAllowedPacket: defaultMaxAllowedPacket, Logger: defaultLogger, AllowNativePasswords: true, CheckConnLiveness: true, ColumnsWithAlias: true, MultiStatements: true},
 }, {
 	"user@unix(/path/to/socket)/dbname?charset=utf8",
-	&Config{User: "user", Net: "unix", Addr: "/path/to/socket", DBName: "dbname", Params: map[string]string{"charset": "utf8"}, Loc: time.UTC, MaxAllowedPacket: defaultMaxAllowedPacket, Logger: defaultLogger, AllowNativePasswords: true, CheckConnLiveness: true},
+	&Config{User: "user", Net: "unix", Addr: "/path/to/socket", DBName: "dbname", charsets: []string{"utf8"}, Loc: time.UTC, MaxAllowedPacket: defaultMaxAllowedPacket, Logger: defaultLogger, AllowNativePasswords: true, CheckConnLiveness: true},
 }, {
 	"user:password@tcp(localhost:5555)/dbname?charset=utf8&tls=true",
-	&Config{User: "user", Passwd: "password", Net: "tcp", Addr: "localhost:5555", DBName: "dbname", Params: map[string]string{"charset": "utf8"}, Loc: time.UTC, MaxAllowedPacket: defaultMaxAllowedPacket, Logger: defaultLogger, AllowNativePasswords: true, CheckConnLiveness: true, TLSConfig: "true"},
+	&Config{User: "user", Passwd: "password", Net: "tcp", Addr: "localhost:5555", DBName: "dbname", charsets: []string{"utf8"}, Loc: time.UTC, MaxAllowedPacket: defaultMaxAllowedPacket, Logger: defaultLogger, AllowNativePasswords: true, CheckConnLiveness: true, TLSConfig: "true"},
 }, {
 	"user:password@tcp(localhost:5555)/dbname?charset=utf8mb4,utf8&tls=skip-verify",
-	&Config{User: "user", Passwd: "password", Net: "tcp", Addr: "localhost:5555", DBName: "dbname", Params: map[string]string{"charset": "utf8mb4,utf8"}, Loc: time.UTC, MaxAllowedPacket: defaultMaxAllowedPacket, Logger: defaultLogger, AllowNativePasswords: true, CheckConnLiveness: true, TLSConfig: "skip-verify"},
+	&Config{User: "user", Passwd: "password", Net: "tcp", Addr: "localhost:5555", DBName: "dbname", charsets: []string{"utf8mb4", "utf8"}, Loc: time.UTC, MaxAllowedPacket: defaultMaxAllowedPacket, Logger: defaultLogger, AllowNativePasswords: true, CheckConnLiveness: true, TLSConfig: "skip-verify"},
 }, {
 	"user:password@/dbname?loc=UTC&timeout=30s&readTimeout=1s&writeTimeout=1s&allowAllFiles=1&clientFoundRows=true&allowOldPasswords=TRUE&collation=utf8mb4_unicode_ci&maxAllowedPacket=16777216&tls=false&allowCleartextPasswords=true&parseTime=true&rejectReadOnly=true",
 	&Config{User: "user", Passwd: "password", Net: "tcp", Addr: "127.0.0.1:3306", DBName: "dbname", Collation: "utf8mb4_unicode_ci", Loc: time.UTC, TLSConfig: "false", AllowCleartextPasswords: true, AllowNativePasswords: true, Timeout: 30 * time.Second, ReadTimeout: time.Second, WriteTimeout: time.Second, Logger: defaultLogger, AllowAllFiles: true, AllowOldPasswords: true, CheckConnLiveness: true, ClientFoundRows: true, MaxAllowedPacket: 16777216, ParseTime: true, RejectReadOnly: true},

packets.go

@@ -316,17 +316,15 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 	data[11] = 0x00
 
 	// Collation ID [1 byte]
-	cname := mc.cfg.Collation
-	if cname == "" {
-		cname = defaultCollation
-	}
-	var found bool
-	data[12], found = collations[cname]
-	if !found {
-		// Note possibility for false negatives:
-		// could be triggered  although the collation is valid if the
-		// collations map does not contain entries the server supports.
-		return fmt.Errorf("unknown collation: %q", cname)
+	data[12] = defaultCollationID
+	if cname := mc.cfg.Collation; cname != "" {
+		colID, ok := collations[cname]
+		if ok {
+			data[12] = colID
+		} else if len(mc.cfg.charsets) > 0 {
+			// When cfg.charset is set, the collation is set by `SET NAMES <charset> COLLATE <collation>`.
+			return fmt.Errorf("unknown collation: %q", cname)
+		}
 	}
 
 	// Filler [23 bytes] (all 0x00)