decode: preserve nanosecond precision when decoding time (#626)

Co-authored-by: Thomas Pelletier <thomas@pelletier.codes>

decode.go

@@ -205,6 +205,7 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		}
 
 		t.Nanosecond = frac * nspow[digits]
+		t.Precision = digits
 
 		return t, b[9+digits:], nil
 	}

internal/imported_tests/unmarshal_imported_test.go

@@ -1514,6 +1514,7 @@ func TestUnmarshalLocalDateTime(t *testing.T) {
 					Minute:     32,
 					Second:     0,
 					Nanosecond: 999999000,
+					Precision:  6,
 				},
 			},
 		},
@@ -1600,6 +1601,7 @@ func TestUnmarshalLocalTime(t *testing.T) {
 				Minute:     32,
 				Second:     0,
 				Nanosecond: 999999000,
+				Precision:  6,
 			},
 		},
 	}

localtime.go

@@ -2,6 +2,7 @@ package toml
 
 import (
 	"fmt"
+	"strings"
 	"time"
 )
 
@@ -40,19 +41,29 @@ func (d *LocalDate) UnmarshalText(b []byte) error {
 // LocalTime represents a time of day of no specific day in no specific
 // timezone.
 type LocalTime struct {
-	Hour       int
+	Hour       int // Hour of the day: [0; 24[
-	Minute     int
+	Minute     int // Minute of the hour: [0; 60[
-	Second     int
+	Second     int // Second of the minute: [0; 60[
-	Nanosecond int
+	Nanosecond int // Nanoseconds within the second:  [0, 1000000000[
+	Precision  int // Number of digits to display for Nanosecond.
 }
 
 // String returns RFC 3339 representation of d.
+// If d.Nanosecond and d.Precision are zero, the time won't have a nanosecond
+// component. If d.Nanosecond > 0 but d.Precision = 0, then the minimum number
+// of digits for nanoseconds is provided.
 func (d LocalTime) String() string {
 	s := fmt.Sprintf("%02d:%02d:%02d", d.Hour, d.Minute, d.Second)
-	if d.Nanosecond == 0 {
+
-		return s
+	if d.Precision > 0 {
+		s += fmt.Sprintf(".%09d", d.Nanosecond)[:d.Precision+1]
+	} else if d.Nanosecond > 0 {
+		// Nanoseconds are specified, but precision is not provided. Use the
+		// minimum.
+		s += strings.Trim(fmt.Sprintf(".%09d", d.Nanosecond), "0")
 	}
-	return s + fmt.Sprintf(".%09d", d.Nanosecond)
+
+	return s
 }
 
 // MarshalText returns RFC 3339 representation of d.

localtime_test.go

@@ -37,14 +37,18 @@ func TestLocalDate_UnmarshalMarshalText(t *testing.T) {
 }
 
 func TestLocalTime_String(t *testing.T) {
-	d := toml.LocalTime{20, 12, 1, 2}
+	d := toml.LocalTime{20, 12, 1, 2, 9}
 	require.Equal(t, "20:12:01.000000002", d.String())
-	d = toml.LocalTime{20, 12, 1, 0}
+	d = toml.LocalTime{20, 12, 1, 0, 0}
 	require.Equal(t, "20:12:01", d.String())
+	d = toml.LocalTime{20, 12, 1, 0, 9}
+	require.Equal(t, "20:12:01.000000000", d.String())
+	d = toml.LocalTime{20, 12, 1, 100, 0}
+	require.Equal(t, "20:12:01.0000001", d.String())
 }
 
 func TestLocalTime_MarshalText(t *testing.T) {
-	d := toml.LocalTime{20, 12, 1, 2}
+	d := toml.LocalTime{20, 12, 1, 2, 9}
 	b, err := d.MarshalText()
 	require.NoError(t, err)
 	require.Equal(t, []byte("20:12:01.000000002"), b)
@@ -54,7 +58,7 @@ func TestLocalTime_UnmarshalMarshalText(t *testing.T) {
 	d := toml.LocalTime{}
 	err := d.UnmarshalText([]byte("20:12:01.000000002"))
 	require.NoError(t, err)
-	require.Equal(t, toml.LocalTime{20, 12, 1, 2}, d)
+	require.Equal(t, toml.LocalTime{20, 12, 1, 2, 9}, d)
 
 	err = d.UnmarshalText([]byte("what"))
 	require.Error(t, err)
@@ -63,10 +67,17 @@ func TestLocalTime_UnmarshalMarshalText(t *testing.T) {
 	require.Error(t, err)
 }
 
+func TestLocalTime_RoundTrip(t *testing.T) {
+	var d struct{ A toml.LocalTime }
+	err := toml.Unmarshal([]byte("a=20:12:01.500"), &d)
+	require.NoError(t, err)
+	require.Equal(t, "20:12:01.500", d.A.String())
+}
+
 func TestLocalDateTime_AsTime(t *testing.T) {
 	d := toml.LocalDateTime{
 		toml.LocalDate{2021, 6, 8},
-		toml.LocalTime{20, 12, 1, 2},
+		toml.LocalTime{20, 12, 1, 2, 9},
 	}
 	cast := d.AsTime(time.UTC)
 	require.Equal(t, time.Date(2021, time.June, 8, 20, 12, 1, 2, time.UTC), cast)
@@ -75,7 +86,7 @@ func TestLocalDateTime_AsTime(t *testing.T) {
 func TestLocalDateTime_String(t *testing.T) {
 	d := toml.LocalDateTime{
 		toml.LocalDate{2021, 6, 8},
-		toml.LocalTime{20, 12, 1, 2},
+		toml.LocalTime{20, 12, 1, 2, 9},
 	}
 	require.Equal(t, "2021-06-08 20:12:01.000000002", d.String())
 }
@@ -83,7 +94,7 @@ func TestLocalDateTime_String(t *testing.T) {
 func TestLocalDateTime_MarshalText(t *testing.T) {
 	d := toml.LocalDateTime{
 		toml.LocalDate{2021, 6, 8},
-		toml.LocalTime{20, 12, 1, 2},
+		toml.LocalTime{20, 12, 1, 2, 9},
 	}
 	b, err := d.MarshalText()
 	require.NoError(t, err)
@@ -96,7 +107,7 @@ func TestLocalDateTime_UnmarshalMarshalText(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, toml.LocalDateTime{
 		toml.LocalDate{2021, 6, 8},
-		toml.LocalTime{20, 12, 1, 2},
+		toml.LocalTime{20, 12, 1, 2, 9},
 	}, d)
 
 	err = d.UnmarshalText([]byte("what"))

unmarshaler_test.go

@@ -331,7 +331,7 @@ func TestUnmarshal(t *testing.T) {
 					expected: &doc{
 						A: toml.LocalDateTime{
 							toml.LocalDate{1979, 5, 27},
-							toml.LocalTime{0, 32, 0, 0},
+							toml.LocalTime{0, 32, 0, 0, 0},
 						},
 					},
 				}
@@ -378,7 +378,7 @@ func TestUnmarshal(t *testing.T) {
 				return test{
 					target: &v,
 					expected: &map[string]interface{}{
-						"a": toml.LocalTime{Hour: 12, Minute: 8, Second: 5, Nanosecond: 666666666},
+						"a": toml.LocalTime{Hour: 12, Minute: 8, Second: 5, Nanosecond: 666666666, Precision: 9},
 					},
 				}
 			},
@@ -2204,42 +2204,57 @@ func TestLocalDateTime(t *testing.T) {
 	examples := []struct {
 		desc  string
 		input string
+		prec  int
 	}{
+		{
+			desc:  "9 digits zero nanoseconds",
+			input: "2006-01-02T15:04:05.000000000",
+			prec:  9,
+		},
 		{
 			desc:  "9 digits",
 			input: "2006-01-02T15:04:05.123456789",
+			prec:  9,
 		},
 		{
 			desc:  "8 digits",
 			input: "2006-01-02T15:04:05.12345678",
+			prec:  8,
 		},
 		{
 			desc:  "7 digits",
 			input: "2006-01-02T15:04:05.1234567",
+			prec:  7,
 		},
 		{
 			desc:  "6 digits",
 			input: "2006-01-02T15:04:05.123456",
+			prec:  6,
 		},
 		{
 			desc:  "5 digits",
 			input: "2006-01-02T15:04:05.12345",
+			prec:  5,
 		},
 		{
 			desc:  "4 digits",
 			input: "2006-01-02T15:04:05.1234",
+			prec:  4,
 		},
 		{
 			desc:  "3 digits",
 			input: "2006-01-02T15:04:05.123",
+			prec:  3,
 		},
 		{
 			desc:  "2 digits",
 			input: "2006-01-02T15:04:05.12",
+			prec:  2,
 		},
 		{
 			desc:  "1 digit",
 			input: "2006-01-02T15:04:05.1",
+			prec:  1,
 		},
 		{
 			desc:  "0 digit",
@@ -2260,7 +2275,7 @@ func TestLocalDateTime(t *testing.T) {
 			require.NoError(t, err)
 			expected := toml.LocalDateTime{
 				toml.LocalDate{golang.Year(), int(golang.Month()), golang.Day()},
-				toml.LocalTime{golang.Hour(), golang.Minute(), golang.Second(), golang.Nanosecond()},
+				toml.LocalTime{golang.Hour(), golang.Minute(), golang.Second(), golang.Nanosecond(), e.prec},
 			}
 			require.Equal(t, expected, actual)
 		})