Merge pull request #41 from georgysavva/add-config-copy

Add Config.Copy() method that returns a smart copy of the config.

config.go

@@ -62,6 +62,35 @@ type Config struct {
 	createdByParseConfig bool // Used to enforce created by ParseConfig rule.
 }
 
+// Copy returns a deep copy of the config that is safe to use and modify.
+// The only exception is the TLSConfig field:
+// according to the tls.Config docs it must not be modified after creation.
+func (c *Config) Copy() *Config {
+	newConf := new(Config)
+	*newConf = *c
+	if newConf.TLSConfig != nil {
+		newConf.TLSConfig = c.TLSConfig.Clone()
+	}
+	if newConf.RuntimeParams != nil {
+		newConf.RuntimeParams = make(map[string]string, len(c.RuntimeParams))
+		for k, v := range c.RuntimeParams {
+			newConf.RuntimeParams[k] = v
+		}
+	}
+	if newConf.Fallbacks != nil {
+		newConf.Fallbacks = make([]*FallbackConfig, len(c.Fallbacks))
+		for i, fallback := range c.Fallbacks {
+			newFallback := new(FallbackConfig)
+			*newFallback = *fallback
+			if newFallback.TLSConfig != nil {
+				newFallback.TLSConfig = fallback.TLSConfig.Clone()
+			}
+			newConf.Fallbacks[i] = newFallback
+		}
+	}
+	return newConf
+}
+
 // FallbackConfig is additional settings to attempt a connection with when the primary Config fails to establish a
 // network connection. It is used for TLS fallback such as sslmode=prefer and high availability (HA) connections.
 type FallbackConfig struct {

config_test.go

@@ -1,6 +1,7 @@
 package pgconn_test
 
 import (
+	"context"
 	"crypto/tls"
 	"fmt"
 	"io/ioutil"
@@ -527,6 +528,44 @@ func TestParseConfig(t *testing.T) {
 	}
 }
 
+func TestConfigCopyReturnsEqualConfig(t *testing.T) {
+	connString := "postgres://jack:secret@localhost:5432/mydb?application_name=pgxtest&search_path=myschema&connect_timeout=5"
+	original, err := pgconn.ParseConfig(connString)
+	require.NoError(t, err)
+
+	copied := original.Copy()
+	assertConfigsEqual(t, original, copied, "Test Config.Copy() returns equal config")
+}
+
+func TestConfigCopyOriginalConfigDidNotChange(t *testing.T) {
+	connString := "postgres://jack:secret@localhost:5432/mydb?application_name=pgxtest&search_path=myschema&connect_timeout=5"
+	original, err := pgconn.ParseConfig(connString)
+	require.NoError(t, err)
+
+	copied := original.Copy()
+	assertConfigsEqual(t, original, copied, "Test Config.Copy() returns equal config")
+
+	copied.Port = uint16(5433)
+	copied.RuntimeParams["foo"] = "bar"
+	copied.Fallbacks[0].Port = uint16(5433)
+
+	assert.Equal(t, uint16(5432), original.Port)
+	assert.Equal(t, "", original.RuntimeParams["foo"])
+	assert.Equal(t, uint16(5432), original.Fallbacks[0].Port)
+}
+
+func TestConfigCopyCanBeUsedToConnect(t *testing.T) {
+	connString := os.Getenv("PGX_TEST_CONN_STRING")
+	original, err := pgconn.ParseConfig(connString)
+	require.NoError(t, err)
+
+	copied := original.Copy()
+	assert.NotPanics(t, func() {
+		_, err = pgconn.ConnectConfig(context.Background(), copied)
+	})
+	assert.NoError(t, err)
+}
+
 func assertConfigsEqual(t *testing.T, expected, actual *pgconn.Config, testName string) {
 	if !assert.NotNil(t, expected) {
 		return