added benchmarks; added lazyError and use lazyError instead of fmt.Errorf

cast_test.go

@@ -827,7 +827,7 @@ func TestToStringMapStringE(t *testing.T) {
 	var interfaceMapString = map[interface{}]string{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}
 	var interfaceMapInterface = map[interface{}]interface{}{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}
 	var jsonString = `{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"}`
-	var invalidJsonString = `{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"`
+	var invalidJSONString = `{"key 1": "value 1", "key 2": "value 2", "key 3": "value 3"`
 	var emptyString = ""
 
 	tests := []struct {
@@ -844,7 +844,7 @@ func TestToStringMapStringE(t *testing.T) {
 		// errors
 		{nil, nil, true},
 		{testing.T{}, nil, true},
-		{invalidJsonString, nil, true},
+		{invalidJSONString, nil, true},
 		{emptyString, nil, true},
 	}
 
@@ -1080,11 +1080,41 @@ func TestToBoolE(t *testing.T) {
 }
 
 func BenchmarkTooBool(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		if !ToBool(true) {
-			b.Fatal("ToBool returned false")
+	b.Run("valid bool(true)", func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			if !ToBool(true) {
+				b.Fatal("ToBool returned false")
+			}
 		}
-	}
+	})
+
+	b.Run("valid bool(1)", func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			if !ToBool(1) {
+				b.Fatal("ToBool returned false")
+			}
+		}
+	})
+
+	b.Run(`invalid bool("xxx")`, func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			if ToBool("xxx") {
+				b.Fatal("ToBool returned true")
+			}
+		}
+	})
+
+	b.Run(`invalid bool(1.0)`, func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			if ToBool(1.0) {
+				b.Fatal("ToBool returned true")
+			}
+		}
+	})
 }
 
 func TestIndirectPointers(t *testing.T) {

caste.go

@@ -7,7 +7,6 @@ package cast
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"html/template"
 	"reflect"
@@ -16,8 +15,6 @@ import (
 	"time"
 )
 
-var errNegativeNotAllowed = errors.New("unable to cast negative value")
-
 // ToTimeE casts an interface to a time.Time type.
 func ToTimeE(i interface{}) (tim time.Time, err error) {
 	i = indirect(i)
@@ -40,7 +37,7 @@ func ToTimeE(i interface{}) (tim time.Time, err error) {
 	case uint32:
 		return time.Unix(int64(v), 0), nil
 	default:
-		return time.Time{}, fmt.Errorf("unable to cast %#v of type %T to Time", i, i)
+		return time.Time{}, newError("unable to cast %#v of type %T to Time", i, i)
 	}
 }
 
@@ -65,7 +62,7 @@ func ToDurationE(i interface{}) (d time.Duration, err error) {
 		}
 		return
 	default:
-		err = fmt.Errorf("unable to cast %#v of type %T to Duration", i, i)
+		err = newError("unable to cast %#v of type %T to Duration", i, i)
 		return
 	}
 }
@@ -87,7 +84,7 @@ func ToBoolE(i interface{}) (bool, error) {
 	case string:
 		return strconv.ParseBool(i.(string))
 	default:
-		return false, fmt.Errorf("unable to cast %#v of type %T to bool", i, i)
+		return false, newError("unable to cast %#v of type %T to bool", i, i)
 	}
 }
 
@@ -125,14 +122,14 @@ func ToFloat64E(i interface{}) (float64, error) {
 		if err == nil {
 			return v, nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v of type %T to float64", i, i)
+		return 0, newError("unable to cast %#v of type %T to float64", i, i)
 	case bool:
 		if s {
 			return 1, nil
 		}
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to float64", i, i)
+		return 0, newError("unable to cast %#v of type %T to float64", i, i)
 	}
 }
 
@@ -170,14 +167,14 @@ func ToFloat32E(i interface{}) (float32, error) {
 		if err == nil {
 			return float32(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v of type %T to float32", i, i)
+		return 0, newError("unable to cast %#v of type %T to float32", i, i)
 	case bool:
 		if s {
 			return 1, nil
 		}
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to float32", i, i)
+		return 0, newError("unable to cast %#v of type %T to float32", i, i)
 	}
 }
 
@@ -215,7 +212,7 @@ func ToInt64E(i interface{}) (int64, error) {
 		if err == nil {
 			return v, nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int64", i, i)
+		return 0, newError("unable to cast %#v of type %T to int64", i, i)
 	case bool:
 		if s {
 			return 1, nil
@@ -224,7 +221,7 @@ func ToInt64E(i interface{}) (int64, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int64", i, i)
+		return 0, newError("unable to cast %#v of type %T to int64", i, i)
 	}
 }
 
@@ -262,7 +259,7 @@ func ToInt32E(i interface{}) (int32, error) {
 		if err == nil {
 			return int32(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int32", i, i)
+		return 0, newError("unable to cast %#v of type %T to int32", i, i)
 	case bool:
 		if s {
 			return 1, nil
@@ -271,7 +268,7 @@ func ToInt32E(i interface{}) (int32, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int32", i, i)
+		return 0, newError("unable to cast %#v of type %T to int32", i, i)
 	}
 }
 
@@ -309,7 +306,7 @@ func ToInt16E(i interface{}) (int16, error) {
 		if err == nil {
 			return int16(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int16", i, i)
+		return 0, newError("unable to cast %#v of type %T to int16", i, i)
 	case bool:
 		if s {
 			return 1, nil
@@ -318,7 +315,7 @@ func ToInt16E(i interface{}) (int16, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int16", i, i)
+		return 0, newError("unable to cast %#v of type %T to int16", i, i)
 	}
 }
 
@@ -356,7 +353,7 @@ func ToInt8E(i interface{}) (int8, error) {
 		if err == nil {
 			return int8(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int8", i, i)
+		return 0, newError("unable to cast %#v of type %T to int8", i, i)
 	case bool:
 		if s {
 			return 1, nil
@@ -365,7 +362,7 @@ func ToInt8E(i interface{}) (int8, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int8", i, i)
+		return 0, newError("unable to cast %#v of type %T to int8", i, i)
 	}
 }
 
@@ -403,7 +400,7 @@ func ToIntE(i interface{}) (int, error) {
 		if err == nil {
 			return int(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int", i, i)
+		return 0, newError("unable to cast %#v of type %T to int", i, i)
 	case bool:
 		if s {
 			return 1, nil
@@ -412,7 +409,7 @@ func ToIntE(i interface{}) (int, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to int", i, i)
+		return 0, newError("unable to cast %#v of type %T to int", i, i)
 	}
 }
 
@@ -426,7 +423,7 @@ func ToUintE(i interface{}) (uint, error) {
 		if err == nil {
 			return uint(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v to uint: %s", i, err)
+		return 0, newError("unable to cast %#v to uint: %s", i, err)
 	case int:
 		if s < 0 {
 			return 0, errNegativeNotAllowed
@@ -480,7 +477,7 @@ func ToUintE(i interface{}) (uint, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to uint", i, i)
+		return 0, newError("unable to cast %#v of type %T to uint", i, i)
 	}
 }
 
@@ -494,7 +491,7 @@ func ToUint64E(i interface{}) (uint64, error) {
 		if err == nil {
 			return v, nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v to uint64: %s", i, err)
+		return 0, newError("unable to cast %#v to uint64: %s", i, err)
 	case int:
 		if s < 0 {
 			return 0, errNegativeNotAllowed
@@ -548,7 +545,7 @@ func ToUint64E(i interface{}) (uint64, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to uint64", i, i)
+		return 0, newError("unable to cast %#v of type %T to uint64", i, i)
 	}
 }
 
@@ -562,7 +559,7 @@ func ToUint32E(i interface{}) (uint32, error) {
 		if err == nil {
 			return uint32(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v to uint32: %s", i, err)
+		return 0, newError("unable to cast %#v to uint32: %s", i, err)
 	case int:
 		if s < 0 {
 			return 0, errNegativeNotAllowed
@@ -616,7 +613,7 @@ func ToUint32E(i interface{}) (uint32, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to uint32", i, i)
+		return 0, newError("unable to cast %#v of type %T to uint32", i, i)
 	}
 }
 
@@ -630,7 +627,7 @@ func ToUint16E(i interface{}) (uint16, error) {
 		if err == nil {
 			return uint16(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v to uint16: %s", i, err)
+		return 0, newError("unable to cast %#v to uint16: %s", i, err)
 	case int:
 		if s < 0 {
 			return 0, errNegativeNotAllowed
@@ -684,7 +681,7 @@ func ToUint16E(i interface{}) (uint16, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to uint16", i, i)
+		return 0, newError("unable to cast %#v of type %T to uint16", i, i)
 	}
 }
 
@@ -698,7 +695,7 @@ func ToUint8E(i interface{}) (uint8, error) {
 		if err == nil {
 			return uint8(v), nil
 		}
-		return 0, fmt.Errorf("unable to cast %#v to uint8: %s", i, err)
+		return 0, newError("unable to cast %#v to uint8: %s", i, err)
 	case int:
 		if s < 0 {
 			return 0, errNegativeNotAllowed
@@ -752,7 +749,7 @@ func ToUint8E(i interface{}) (uint8, error) {
 	case nil:
 		return 0, nil
 	default:
-		return 0, fmt.Errorf("unable to cast %#v of type %T to uint8", i, i)
+		return 0, newError("unable to cast %#v of type %T to uint8", i, i)
 	}
 }
 
@@ -847,7 +844,7 @@ func ToStringE(i interface{}) (string, error) {
 	case error:
 		return s.Error(), nil
 	default:
-		return "", fmt.Errorf("unable to cast %#v of type %T to string", i, i)
+		return "", newError("unable to cast %#v of type %T to string", i, i)
 	}
 }
 
@@ -877,7 +874,7 @@ func ToStringMapStringE(i interface{}) (map[string]string, error) {
 		err := jsonStringToObject(v, &m)
 		return m, err
 	default:
-		return m, fmt.Errorf("unable to cast %#v of type %T to map[string]string", i, i)
+		return m, newError("unable to cast %#v of type %T to map[string]string", i, i)
 	}
 }
 
@@ -928,11 +925,11 @@ func ToStringMapStringSliceE(i interface{}) (map[string][]string, error) {
 		for k, val := range v {
 			key, err := ToStringE(k)
 			if err != nil {
-				return m, fmt.Errorf("unable to cast %#v of type %T to map[string][]string", i, i)
+				return m, newError("unable to cast %#v of type %T to map[string][]string", i, i)
 			}
 			value, err := ToStringSliceE(val)
 			if err != nil {
-				return m, fmt.Errorf("unable to cast %#v of type %T to map[string][]string", i, i)
+				return m, newError("unable to cast %#v of type %T to map[string][]string", i, i)
 			}
 			m[key] = value
 		}
@@ -940,7 +937,7 @@ func ToStringMapStringSliceE(i interface{}) (map[string][]string, error) {
 		err := jsonStringToObject(v, &m)
 		return m, err
 	default:
-		return m, fmt.Errorf("unable to cast %#v of type %T to map[string][]string", i, i)
+		return m, newError("unable to cast %#v of type %T to map[string][]string", i, i)
 	}
 	return m, nil
 }
@@ -966,7 +963,7 @@ func ToStringMapBoolE(i interface{}) (map[string]bool, error) {
 		err := jsonStringToObject(v, &m)
 		return m, err
 	default:
-		return m, fmt.Errorf("unable to cast %#v of type %T to map[string]bool", i, i)
+		return m, newError("unable to cast %#v of type %T to map[string]bool", i, i)
 	}
 }
 
@@ -986,7 +983,7 @@ func ToStringMapE(i interface{}) (map[string]interface{}, error) {
 		err := jsonStringToObject(v, &m)
 		return m, err
 	default:
-		return m, fmt.Errorf("unable to cast %#v of type %T to map[string]interface{}", i, i)
+		return m, newError("unable to cast %#v of type %T to map[string]interface{}", i, i)
 	}
 }
 
@@ -1003,14 +1000,14 @@ func ToSliceE(i interface{}) ([]interface{}, error) {
 		}
 		return s, nil
 	default:
-		return s, fmt.Errorf("unable to cast %#v of type %T to []interface{}", i, i)
+		return s, newError("unable to cast %#v of type %T to []interface{}", i, i)
 	}
 }
 
 // ToBoolSliceE casts an interface to a []bool type.
 func ToBoolSliceE(i interface{}) ([]bool, error) {
 	if i == nil {
-		return []bool{}, fmt.Errorf("unable to cast %#v of type %T to []bool", i, i)
+		return []bool{}, newError("unable to cast %#v of type %T to []bool", i, i)
 	}
 
 	switch v := i.(type) {
@@ -1026,13 +1023,13 @@ func ToBoolSliceE(i interface{}) ([]bool, error) {
 		for j := 0; j < s.Len(); j++ {
 			val, err := ToBoolE(s.Index(j).Interface())
 			if err != nil {
-				return []bool{}, fmt.Errorf("unable to cast %#v of type %T to []bool", i, i)
+				return []bool{}, newError("unable to cast %#v of type %T to []bool", i, i)
 			}
 			a[j] = val
 		}
 		return a, nil
 	default:
-		return []bool{}, fmt.Errorf("unable to cast %#v of type %T to []bool", i, i)
+		return []bool{}, newError("unable to cast %#v of type %T to []bool", i, i)
 	}
 }
 
@@ -1053,18 +1050,18 @@ func ToStringSliceE(i interface{}) ([]string, error) {
 	case interface{}:
 		str, err := ToStringE(v)
 		if err != nil {
-			return a, fmt.Errorf("unable to cast %#v of type %T to []string", i, i)
+			return a, newError("unable to cast %#v of type %T to []string", i, i)
 		}
 		return []string{str}, nil
 	default:
-		return a, fmt.Errorf("unable to cast %#v of type %T to []string", i, i)
+		return a, newError("unable to cast %#v of type %T to []string", i, i)
 	}
 }
 
 // ToIntSliceE casts an interface to a []int type.
 func ToIntSliceE(i interface{}) ([]int, error) {
 	if i == nil {
-		return []int{}, fmt.Errorf("unable to cast %#v of type %T to []int", i, i)
+		return []int{}, newError("unable to cast %#v of type %T to []int", i, i)
 	}
 
 	switch v := i.(type) {
@@ -1080,20 +1077,20 @@ func ToIntSliceE(i interface{}) ([]int, error) {
 		for j := 0; j < s.Len(); j++ {
 			val, err := ToIntE(s.Index(j).Interface())
 			if err != nil {
-				return []int{}, fmt.Errorf("unable to cast %#v of type %T to []int", i, i)
+				return []int{}, newError("unable to cast %#v of type %T to []int", i, i)
 			}
 			a[j] = val
 		}
 		return a, nil
 	default:
-		return []int{}, fmt.Errorf("unable to cast %#v of type %T to []int", i, i)
+		return []int{}, newError("unable to cast %#v of type %T to []int", i, i)
 	}
 }
 
 // ToDurationSliceE casts an interface to a []time.Duration type.
 func ToDurationSliceE(i interface{}) ([]time.Duration, error) {
 	if i == nil {
-		return []time.Duration{}, fmt.Errorf("unable to cast %#v of type %T to []time.Duration", i, i)
+		return []time.Duration{}, newError("unable to cast %#v of type %T to []time.Duration", i, i)
 	}
 
 	switch v := i.(type) {
@@ -1109,13 +1106,13 @@ func ToDurationSliceE(i interface{}) ([]time.Duration, error) {
 		for j := 0; j < s.Len(); j++ {
 			val, err := ToDurationE(s.Index(j).Interface())
 			if err != nil {
-				return []time.Duration{}, fmt.Errorf("unable to cast %#v of type %T to []time.Duration", i, i)
+				return []time.Duration{}, newError("unable to cast %#v of type %T to []time.Duration", i, i)
 			}
 			a[j] = val
 		}
 		return a, nil
 	default:
-		return []time.Duration{}, fmt.Errorf("unable to cast %#v of type %T to []time.Duration", i, i)
+		return []time.Duration{}, newError("unable to cast %#v of type %T to []time.Duration", i, i)
 	}
 }
 
@@ -1155,7 +1152,7 @@ func parseDateWith(s string, dates []string) (d time.Time, e error) {
 			return
 		}
 	}
-	return d, fmt.Errorf("unable to parse date: %s", s)
+	return d, newError("unable to parse date: %s", s)
 }
 
 // jsonStringToObject attempts to unmarshall a string as JSON into

errors.go

@@ -0,0 +1,30 @@
+package cast
+
+import (
+	"errors"
+	"fmt"
+	"sync"
+)
+
+var errNegativeNotAllowed = errors.New("unable to cast negative value")
+
+type lazyError struct {
+	format string
+	args   []interface{}
+	once   sync.Once
+	result string
+}
+
+func (e *lazyError) Error() string {
+	e.once.Do(func() {
+		e.result = fmt.Sprintf(e.format, e.args...)
+	})
+	return e.result
+}
+
+func newError(format string, args ...interface{}) error {
+	return &lazyError{
+		format: format,
+		args:   args,
+	}
+}

errors_test.go

@@ -0,0 +1,13 @@
+package cast
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestLazyError_Error(t *testing.T) {
+	err := newError("foo")
+
+	assert.NotNil(t, err)
+	assert.Equal(t, err.Error(), "foo")
+}