Add an option to disable usage of stringer methods.

config.go

@@ -76,6 +76,15 @@ func SnapshotFileExtension(snapshotFileExtension string) Configurator {
 	}
 }
 
+// UseStringerMethods invoke String() or Error() methods when available rather than dumping the object.
+// This should probably be disabled by default but is not for backwards compatibility reasons.
+// Default: true
+func UseStringerMethods(useStringerMethods bool) Configurator {
+	return func(c *Config) {
+		c.useStringerMethods = useStringerMethods
+	}
+}
+
 // Config provides the same snapshotting functions with additional configuration capabilities.
 type Config struct {
 	shouldUpdate           func() bool
@@ -84,6 +93,7 @@ type Config struct {
 	createNewAutomatically bool
 	fatalOnMismatch        bool
 	snapshotFileExtension  string
+	useStringerMethods     bool
 }
 
 // NewDefaultConfig returns a new Config instance initialised with the same options as
@@ -96,6 +106,7 @@ func NewDefaultConfig() *Config {
 		CreateNewAutomatically(true),
 		FatalOnMismatch(false),
 		SnapshotFileExtension(""),
+		UseStringerMethods(true),
 	)
 }
 
@@ -110,5 +121,6 @@ func (c *Config) clone() *Config {
 		createNewAutomatically: c.createNewAutomatically,
 		fatalOnMismatch:        c.fatalOnMismatch,
 		snapshotFileExtension:  c.snapshotFileExtension,
+		useStringerMethods:     c.useStringerMethods,
 	}
 }

cupaloy.go

@@ -98,7 +98,7 @@ func (c *Config) WithOptions(configurators ...Configurator) *Config {
 }
 
 func (c *Config) snapshot(snapshotName string, i ...interface{}) error {
-	snapshot := takeSnapshot(i...)
+	snapshot := c.takeSnapshot(i...)
 
 	prevSnapshot, err := c.readSnapshot(snapshotName)
 	if os.IsNotExist(err) {
@@ -111,7 +111,7 @@ func (c *Config) snapshot(snapshotName string, i ...interface{}) error {
 		return err
 	}
 
-	if snapshot == prevSnapshot || takeV1Snapshot(i...) == prevSnapshot {
+	if snapshot == prevSnapshot || c.takeV1Snapshot(i...) == prevSnapshot {
 		// previous snapshot matches current value
 		return nil
 	}

examples/.snapshots/TestUseStringerMethods-disabled

@@ -0,0 +1,2 @@
+(examples_test.stringer) {
+}

examples/.snapshots/TestUseStringerMethods-enabled

@@ -0,0 +1 @@
+(examples_test.stringer) with stringer

examples/advanced_test.go

@@ -2,11 +2,12 @@ package examples_test
 
 import (
 	"bytes"
-	"github.com/bradleyjkemp/cupaloy/v2/internal"
 	"io/ioutil"
 	"strings"
 	"testing"
 
+	"github.com/bradleyjkemp/cupaloy/v2/internal"
+
 	"github.com/bradleyjkemp/cupaloy/v2"
 	"github.com/stretchr/testify/mock"
 )
@@ -65,7 +66,6 @@ func TestUpdate(t *testing.T) {
 		t.Fatalf("Error returned will be of type ErrSnapshotUpdated")
 	}
 
-
 }
 
 // If a snapshot doesn't exist then it is created and an error returned
@@ -209,3 +209,22 @@ func TestSnapshotFileExtension(t *testing.T) {
 	snapshotter := cupaloy.New(cupaloy.SnapshotFileExtension(".myextension"))
 	snapshotter.SnapshotT(t, "This should end up in a file with extension .myextension")
 }
+
+type stringer struct {
+}
+
+func (s stringer) String() string {
+	return "with stringer"
+}
+
+func TestUseStringerMethods(t *testing.T) {
+	s := stringer{}
+
+	t.Run("enabled", func(t *testing.T) {
+		cupaloy.New(cupaloy.UseStringerMethods(true)).SnapshotT(t, s)
+	})
+
+	t.Run("disabled", func(t *testing.T) {
+		cupaloy.New(cupaloy.UseStringerMethods(false)).SnapshotT(t, s)
+	})
+}

util.go

@@ -15,14 +15,6 @@ import (
 	"github.com/pmezard/go-difflib/difflib"
 )
 
-var spewConfig = spew.ConfigState{
-	Indent:                  "  ",
-	SortKeys:                true, // maps should be spewed in a deterministic order
-	DisablePointerAddresses: true, // don't spew the addresses of pointers
-	DisableCapacities:       true, // don't spew capacities of collections
-	SpewKeys:                true, // if unable to sort map keys then spew keys to strings and sort those
-}
-
 //go:generate $GOPATH/bin/mockery -output=examples -outpkg=examples_test -testonly -name=TestingT
 
 // TestingT is a subset of the interface testing.TB allowing it to be mocked in tests.
@@ -47,17 +39,28 @@ func envVariableSet(envVariable string) bool {
 	return varSet
 }
 
+func (c *Config) getSpewConfig() *spew.ConfigState {
+	return &spew.ConfigState{
+		Indent:                  "  ",
+		SortKeys:                true, // maps should be spewed in a deterministic order
+		DisablePointerAddresses: true, // don't spew the addresses of pointers
+		DisableCapacities:       true, // don't spew capacities of collections
+		SpewKeys:                true, // if unable to sort map keys then spew keys to strings and sort those
+		DisableMethods:          !c.useStringerMethods,
+	}
+}
+
 func (c *Config) snapshotFilePath(testName string) string {
 	return filepath.Join(c.subDirName, testName+c.snapshotFileExtension)
 }
 
 // Legacy snapshot format where all items were spewed
-func takeV1Snapshot(i ...interface{}) string {
-	return spewConfig.Sdump(i...)
+func (c *Config) takeV1Snapshot(i ...interface{}) string {
+	return c.getSpewConfig().Sdump(i...)
 }
 
 // New snapshot format where some types are written out raw to the file
-func takeSnapshot(i ...interface{}) string {
+func (c *Config) takeSnapshot(i ...interface{}) string {
 	snapshot := &bytes.Buffer{}
 	for _, v := range i {
 		switch vt := v.(type) {
@@ -68,7 +71,7 @@ func takeSnapshot(i ...interface{}) string {
 			snapshot.Write(vt)
 			snapshot.WriteString("\n")
 		default:
-			spewConfig.Fdump(snapshot, v)
+			c.getSpewConfig().Fdump(snapshot, v)
 		}
 	}