Parameterize UnknownEnumValueError

Also, do not sort the expected values in UnknownEnumValueError.Error.

2 files changed, 12 insertions, 23 deletions

diff --git a/flag.go b/flag.go
index 18d9f96..f9d048e 100644
--- a/flag.go
+++ b/flag.go
@@ -7,7 +7,6 @@ import (
 	"flag"
 	"fmt"
 	"os"
-	"sort"
 	"strconv"
 	"strings"
 	"sync/atomic"
@@ -156,14 +155,10 @@ type ParseFunc[T any] func(string) (T, error)
 // https://developers.google.com/protocol-buffers/docs/reference/go-generated#enum
 // for more details.
 func ParseProtobufEnum[T ~int32](values map[string]int32) ParseFunc[T] {
-	valid := make([]string, 0, len(values))
-	for val := range values {
-		valid = append(valid, val)
-	}
 	return func(s string) (T, error) {
 		val, found := values[strings.ToUpper(s)]
 		if !found {
-			return 0, UnknownEnumValueError{s, valid}
+			return 0, UnknownEnumValueError[string]{s, MapKeys(values)}
 		}
 		return T(val), nil
 	}
@@ -185,7 +180,7 @@ func ParseStringEnum(values ...string) ParseFunc[string] {
 				return s, nil
 			}
 		}
-		return "", UnknownEnumValueError{s, values}
+		return "", UnknownEnumValueError[string]{s, values}
 	}
 }
 
@@ -197,18 +192,13 @@ func ParseTime(s string) (time.Time, error) {
 // UnknownEnumValueError is returned by the functions produced by
 // ParseProtobufEnum and ParseStringEnum when an unknown value is
 // encountered.
-type UnknownEnumValueError struct {
+type UnknownEnumValueError[T any] struct {
 	Actual   string
-	Expected []string
+	Expected []T
 }
 
-func (err UnknownEnumValueError) Error() string {
-	// We sort the expected values so the output is deterministic, which may
-	// be useful when parsing logs or otherwise examining program output.
-	if !sort.StringsAreSorted(err.Expected) {
-		sort.Strings(err.Expected)
-	}
-	return fmt.Sprintf("unknown value %s, expected one of %s", err.Actual, err.Expected)
+func (err UnknownEnumValueError[T]) Error() string {
+	return fmt.Sprintf("unknown value %s, expected one of %v", err.Actual, err.Expected)
 }
 
 type flagFeature struct{ *Feature }
diff --git a/flag_test.go b/flag_test.go
index 5b0df0e..3273775 100644
--- a/flag_test.go
+++ b/flag_test.go
@@ -5,10 +5,11 @@ package core_test
 
 import (
 	"flag"
-	"sort"
 	"strconv"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
+
 	"go.awhk.org/core"
 )
 
@@ -144,7 +145,7 @@ func TestInitFlagSet(s *testing.T) {
 }
 
 func TestParseProtobufEnum(s *testing.T) {
-	t := &core.T{T: s}
+	t := &core.T{T: s, Options: cmp.Options{sortStrings}}
 
 	// That type and map emulate code generated by protoc.
 	type fakeEnum int32
@@ -169,10 +170,9 @@ func TestParseProtobufEnum(s *testing.T) {
 
 	t.Run("UnknownValue", func(t *core.T) {
 		val, err := parse("BAZ")
-		var exp core.UnknownEnumValueError
+		var exp core.UnknownEnumValueError[string]
 		if t.AssertErrorAs(&exp, err) {
 			t.AssertEqual("BAZ", exp.Actual)
-			sort.Strings(exp.Expected)
 			t.AssertEqual([]string{"BAR", "FAKE_UNKNOWN", "FOO"}, exp.Expected)
 		}
 		t.AssertEqual(fakeEnum(0), val)
@@ -195,11 +195,10 @@ func TestParseStringEnum(s *testing.T) {
 
 	t.Run("UnknownValue", func(t *core.T) {
 		val, err := parse("baz")
-		var exp core.UnknownEnumValueError
+		var exp core.UnknownEnumValueError[string]
 		if t.AssertErrorAs(&exp, err) {
 			t.AssertEqual("baz", exp.Actual)
-			sort.Strings(exp.Expected)
-			t.AssertEqual([]string{"bar", "foo"}, exp.Expected)
+			t.AssertEqual([]string{"foo", "bar"}, exp.Expected)
 		}
 		t.AssertEqual("", val)
 	})