feat: honour TextMarshaler and TextUnmarshaler by default

Assisted-by: DeepSeek V4.1 Flash

decode_test.go

@@ -8,9 +8,11 @@ import (
 	"errors"
 	"fmt"
 	"math"
+	"net"
 	"slices"
 	"strings"
 	"testing"
+	"time"
 )
 
 func TestSyntaxErrorMessage(t *testing.T) {
@@ -747,3 +749,205 @@ func TestUnmarshalIntoDefinedScalarTypes(t *testing.T) {
 		t.Error("F = false, want true")
 	}
 }
+
+// --- encoding.TextUnmarshaler and time.Duration ----------------------------
+
+// textReceiver implements encoding.TextUnmarshaler on the pointer receiver.
+type textReceiver struct{ Text string }
+
+func (t *textReceiver) UnmarshalText(text []byte) error {
+	t.Text = "got:" + string(text)
+	return nil
+}
+
+// upperText is a defined string type whose UnmarshalText transforms the
+// content, so a plain string assignment would leave the wrong value behind.
+type upperText string
+
+func (u *upperText) UnmarshalText(text []byte) error {
+	*u = upperText(strings.ToUpper(string(text)))
+	return nil
+}
+
+// failingTextUnmarshaler fails the decode from UnmarshalText.
+type failingTextUnmarshaler struct{}
+
+func (f *failingTextUnmarshaler) UnmarshalText(_ []byte) error { return errors.New("text boom") }
+
+// textAndTOMLReceiver implements both decode interfaces; the TOML method wins.
+type textAndTOMLReceiver struct{ From string }
+
+func (t *textAndTOMLReceiver) UnmarshalTOML(any) error { t.From = "toml"; return nil }
+
+func (t *textAndTOMLReceiver) UnmarshalText([]byte) error { t.From = "text"; return nil }
+
+func TestTextUnmarshalerByPointer(t *testing.T) {
+	type Cfg struct {
+		R textReceiver `toml:"r"`
+	}
+	var cfg Cfg
+	if err := Unmarshal([]byte(`r = "hello"`), &cfg); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if cfg.R.Text != "got:hello" {
+		t.Errorf("Text = %q, want \"got:hello\"", cfg.R.Text)
+	}
+}
+
+func TestTextUnmarshalerWinsOverKindAssignment(t *testing.T) {
+	type Cfg struct {
+		U upperText `toml:"u"`
+	}
+	var cfg Cfg
+	if err := Unmarshal([]byte(`u = "abc"`), &cfg); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if cfg.U != "ABC" {
+		t.Errorf("U = %q, want \"ABC\"", cfg.U)
+	}
+}
+
+func TestTextUnmarshalerForNetIP(t *testing.T) {
+	type Cfg struct {
+		V4  net.IP   `toml:"v4"`
+		V6  net.IP   `toml:"v6"`
+		IPs []net.IP `toml:"ips"`
+	}
+	in := "v4 = \"192.0.2.1\"\nv6 = \"2001:db8::68\"\nips = [\"198.51.100.7\", \"203.0.113.9\"]\n"
+	var cfg Cfg
+	if err := Unmarshal([]byte(in), &cfg); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if got := cfg.V4.String(); got != "192.0.2.1" {
+		t.Errorf("V4 = %q, want \"192.0.2.1\"", got)
+	}
+	if got := cfg.V6.String(); got != "2001:db8::68" {
+		t.Errorf("V6 = %q, want \"2001:db8::68\"", got)
+	}
+	if len(cfg.IPs) != 2 || cfg.IPs[0].String() != "198.51.100.7" || cfg.IPs[1].String() != "203.0.113.9" {
+		t.Errorf("IPs = %v, want two addresses", cfg.IPs)
+	}
+}
+
+func TestTextUnmarshalerSeesStringsOnly(t *testing.T) {
+	// An integer keeps its own rule: the text method is not consulted, and the
+	// value does not reach the receiver.
+	type Cfg struct {
+		R textReceiver `toml:"r"`
+	}
+	var cfg Cfg
+	err := Unmarshal([]byte("r = 1\n"), &cfg)
+	if err == nil {
+		t.Fatal("expected an integer to be rejected for a text receiver")
+	}
+	if cfg.R.Text != "" {
+		t.Errorf("Text = %q, want it untouched", cfg.R.Text)
+	}
+}
+
+func TestUnmarshalTOMLWinsOverTextUnmarshaler(t *testing.T) {
+	type Cfg struct {
+		B textAndTOMLReceiver `toml:"b"`
+	}
+	var cfg Cfg
+	if err := Unmarshal([]byte(`b = "x"`), &cfg); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if cfg.B.From != "toml" {
+		t.Errorf("From = %q, want \"toml\"", cfg.B.From)
+	}
+}
+
+func TestTextUnmarshalerErrorCarriesPath(t *testing.T) {
+	type Inner struct {
+		F failingTextUnmarshaler `toml:"f"`
+	}
+	type Cfg struct {
+		Inner Inner `toml:"inner"`
+	}
+	var cfg Cfg
+	err := Unmarshal([]byte("[inner]\nf = \"x\"\n"), &cfg)
+	if err == nil {
+		t.Fatal("expected an error from UnmarshalText")
+	}
+	if !strings.Contains(err.Error(), "unmarshal text: text boom") {
+		t.Errorf("err = %v, want the text error wrapped", err)
+	}
+	de, ok := errors.AsType[*DecodeError](err)
+	if !ok {
+		t.Fatalf("expected a *DecodeError, got %T: %v", err, err)
+	}
+	if !slices.Equal(de.Path, []string{"inner", "f"}) {
+		t.Fatalf("Path = %v, want [inner f]", de.Path)
+	}
+}
+
+func TestTextUnmarshalerReportsBadText(t *testing.T) {
+	var cfg struct {
+		IP net.IP `toml:"ip"`
+	}
+	err := Unmarshal([]byte(`ip = "not-an-ip"`), &cfg)
+	if err == nil {
+		t.Fatal("expected an error for a malformed address")
+	}
+	if !strings.Contains(err.Error(), "unmarshal text:") {
+		t.Errorf("err = %v, want it wrapped as a text error", err)
+	}
+}
+
+func TestUnmarshalDurations(t *testing.T) {
+	type Cfg struct {
+		FromText time.Duration `toml:"from_text"`
+		FromInt  time.Duration `toml:"from_int"`
+		Fraction time.Duration `toml:"fraction"`
+	}
+	in := "from_text = \"1h30m\"\nfrom_int = 5400000000000\nfraction = \"1.5s\"\n"
+	var cfg Cfg
+	if err := Unmarshal([]byte(in), &cfg); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if cfg.FromText != 90*time.Minute {
+		t.Errorf("FromText = %v, want %v", cfg.FromText, 90*time.Minute)
+	}
+	if cfg.FromInt != 90*time.Minute {
+		t.Errorf("FromInt = %v, want %v", cfg.FromInt, 90*time.Minute)
+	}
+	if cfg.Fraction != 1500*time.Millisecond {
+		t.Errorf("Fraction = %v, want %v", cfg.Fraction, 1500*time.Millisecond)
+	}
+}
+
+func TestUnmarshalDurationRejectsMalformedText(t *testing.T) {
+	var cfg struct {
+		D time.Duration `toml:"d"`
+	}
+	err := Unmarshal([]byte("d = \"90\"\n"), &cfg)
+	if err == nil {
+		t.Fatal("expected an error for a duration without a unit")
+	}
+	if !strings.Contains(err.Error(), "invalid duration") {
+		t.Errorf("err = %v, want an invalid-duration message", err)
+	}
+}
+
+func TestQuotedStringNeverBecomesDateTime(t *testing.T) {
+	// The date-time types take a bare timestamp only, so the text path is
+	// excluded for them and a quoted string stays a string.
+	var stamp struct {
+		S time.Time `toml:"s"`
+	}
+	err := Unmarshal([]byte("s = \"2026-06-26T10:00:00Z\"\n"), &stamp)
+	if err == nil {
+		t.Fatal("expected a quoted string to be rejected for time.Time")
+	}
+	if !strings.Contains(err.Error(), "cannot assign string") {
+		t.Errorf("err = %v, want a cannot-assign message", err)
+	}
+
+	var day struct {
+		D LocalDate `toml:"d"`
+	}
+	if err := Unmarshal([]byte("d = \"1979-05-27\"\n"), &day); err == nil {
+		t.Fatal("expected a quoted string to be rejected for LocalDate")
+	}
+}