Implement deep copy manually, stop using an external deep copy library. Add comment to the Config.Copy() method.

config.go

@@ -17,8 +17,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/mohae/deepcopy"
-
 	"github.com/jackc/chunkreader/v2"
 	"github.com/jackc/pgpassfile"
 	"github.com/jackc/pgproto3/v2"
@@ -64,10 +62,32 @@ 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 := deepcopy.Copy(c).(*Config)
-	// We need to set this field manually because it's unexported and deep copy won't touch it.
-	newConf.createdByParseConfig = c.createdByParseConfig
+	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
 }
 

config_test.go

@@ -529,7 +529,7 @@ func TestParseConfig(t *testing.T) {
 }
 
 func TestConfigCopyReturnsEqualConfig(t *testing.T) {
-	connString := "postgres://jack:secret@localhost:5432/mydb?sslmode=disable&application_name=pgxtest&search_path=myschema&connect_timeout=5"
+	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)
 
@@ -538,14 +538,20 @@ func TestConfigCopyReturnsEqualConfig(t *testing.T) {
 }
 
 func TestConfigCopyOriginalConfigDidNotChange(t *testing.T) {
-	connString := "postgres://jack:secret@localhost:5432/mydb?sslmode=disable&application_name=pgxtest&search_path=myschema&connect_timeout=5"
+	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) {

go.mod

@@ -9,7 +9,6 @@ require (
 	github.com/jackc/pgpassfile v1.0.0
 	github.com/jackc/pgproto3/v2 v2.0.1
 	github.com/jackc/pgservicefile v0.0.0-20200307190119-3430c5407db8
-	github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826
 	github.com/stretchr/testify v1.5.1
 	golang.org/x/crypto v0.0.0-20200323165209-0ec3e9974c59
 	golang.org/x/text v0.3.2

go.sum

@@ -54,8 +54,6 @@ github.com/lib/pq v1.2.0/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=
 github.com/mattn/go-colorable v0.1.1/go.mod h1:FuOcm+DKB9mbwrcAfNl7/TZVBZ6rcnceauSikq3lYCQ=
 github.com/mattn/go-isatty v0.0.5/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
 github.com/mattn/go-isatty v0.0.7/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
-github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826 h1:RWengNIwukTxcDr9M+97sNutRR1RKhG96O6jWumTTnw=
-github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826/go.mod h1:TaXosZuwdSHYgviHp1DAtfrULt5eUgsSMsZf+YrPgl8=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=