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time: support "," as separator for fractional seconds
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Accepts comma "," as a separator for fractional seconds
hence we now accept:
* 2006-01-02 15:04:05,999999999 -0700 MST
* Mon Jan _2 15:04:05,120007 2006
* Mon Jan 2 15:04:05,120007 2006

This change follows the recommendations of ISO 8601 per

   https://en.wikipedia.org/wiki/ISO_8601#cite_note-26

which states

   ISO 8601:2004(E), ISO, 2004-12-01, "4.2.2.4 ...
   the decimal fraction shall be divided from the integer
   part by the decimal sign specified in ISO 31-0, i.e.
   the comma [,] or full stop [.]. Of these, the comma
   is the preferred sign."

Unfortunately, I couldn't directly access the ISO 8601 document
because suddenly it is behind a paywall on the ISO website,
charging CHF 158 (USD 179) for 38 pages :-(

However, this follows publicly available cited literature, as well
as the recommendations from the proposal approval.

Fixes #6189
Updates #27746
Updates #26002
Updates #36145
Updates #43813
Fixes #43823

Change-Id: Ibe96064e8ee27c239be78c880fa561a1a41e190c
Reviewed-on: https://go-review.googlesource.com/c/go/+/300996
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Rob Pike <r@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
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@odeke-em
odeke-em committed Mar 16, 2021
1 parent a9b3c4b commit f02a26b
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Showing 2 changed files with 33 additions and 15 deletions.
30 changes: 18 additions & 12 deletions src/time/format.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,13 +26,14 @@ import "errors"
// compatibility with fixed-width Unix time formats.
//
// A decimal point followed by one or more zeros represents a fractional
// second, printed to the given number of decimal places. A decimal point
// followed by one or more nines represents a fractional second, printed to
// the given number of decimal places, with trailing zeros removed.
// second, printed to the given number of decimal places.
// Either a comma or decimal point followed by one or more nines represents
// a fractional second, printed to the given number of decimal places, with
// trailing zeros removed.
// When parsing (only), the input may contain a fractional second
// field immediately after the seconds field, even if the layout does not
// signify its presence. In that case a decimal point followed by a maximal
// series of digits is parsed as a fractional second.
// signify its presence. In that case either a comma or a decimal point
// followed by a maximal series of digits is parsed as a fractional second.
//
// Numeric time zone offsets format as follows:
// -0700 ±hhmm
Expand Down Expand Up @@ -261,7 +262,7 @@ func nextStdChunk(layout string) (prefix string, std int, suffix string) {
return layout[0:i], stdISO8601ShortTZ, layout[i+3:]
}

case '.': // .000 or .999 - repeated digits for fractional seconds.
case '.', ',': // ,000, or .000, or ,999, or .999 - repeated digits for fractional seconds.
if i+1 < len(layout) && (layout[i+1] == '0' || layout[i+1] == '9') {
ch := layout[i+1]
j := i + 1
Expand Down Expand Up @@ -484,9 +485,10 @@ func (t Time) String() string {
// desired output. The same display rules will then be applied to the time
// value.
//
// A fractional second is represented by adding a period and zeros
// to the end of the seconds section of layout string, as in "15:04:05.000"
// to format a time stamp with millisecond precision.
// A fractional second is represented by adding either a comma or a
// period and zeros to the end of the seconds section of layout string,
// as in "15:04:05,000" or "15:04:05.000" to format a time stamp with
// millisecond precision.
//
// Predefined layouts ANSIC, UnixDate, RFC3339 and others describe standard
// and convenient representations of the reference time. For more information
Expand Down Expand Up @@ -940,7 +942,7 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
}
// Special case: do we have a fractional second but no
// fractional second in the format?
if len(value) >= 2 && value[0] == '.' && isDigit(value, 1) {
if len(value) >= 2 && commaOrPeriod(value[0]) && isDigit(value, 1) {
_, std, _ = nextStdChunk(layout)
std &= stdMask
if std == stdFracSecond0 || std == stdFracSecond9 {
Expand Down Expand Up @@ -1070,7 +1072,7 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
value = value[ndigit:]

case stdFracSecond9:
if len(value) < 2 || value[0] != '.' || value[1] < '0' || '9' < value[1] {
if len(value) < 2 || !commaOrPeriod(value[0]) || value[1] < '0' || '9' < value[1] {
// Fractional second omitted.
break
}
Expand Down Expand Up @@ -1279,8 +1281,12 @@ func parseSignedOffset(value string) int {
return len(value) - len(rem)
}

func commaOrPeriod(b byte) bool {
return b == '.' || b == ','
}

func parseNanoseconds(value string, nbytes int) (ns int, rangeErrString string, err error) {
if value[0] != '.' {
if !commaOrPeriod(value[0]) {
err = errBad
return
}
Expand Down
18 changes: 15 additions & 3 deletions src/time/format_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -207,9 +207,13 @@ var parseTests = []ParseTest{
{"ANSIC", ANSIC, "THU FEB 4 21:00:57 2010", false, true, 1, 0},
{"ANSIC", ANSIC, "thu feb 4 21:00:57 2010", false, true, 1, 0},
// Fractional seconds.
{"millisecond", "Mon Jan _2 15:04:05.000 2006", "Thu Feb 4 21:00:57.012 2010", false, true, 1, 3},
{"microsecond", "Mon Jan _2 15:04:05.000000 2006", "Thu Feb 4 21:00:57.012345 2010", false, true, 1, 6},
{"nanosecond", "Mon Jan _2 15:04:05.000000000 2006", "Thu Feb 4 21:00:57.012345678 2010", false, true, 1, 9},
{"millisecond:: dot separator", "Mon Jan _2 15:04:05.000 2006", "Thu Feb 4 21:00:57.012 2010", false, true, 1, 3},
{"microsecond:: dot separator", "Mon Jan _2 15:04:05.000000 2006", "Thu Feb 4 21:00:57.012345 2010", false, true, 1, 6},
{"nanosecond:: dot separator", "Mon Jan _2 15:04:05.000000000 2006", "Thu Feb 4 21:00:57.012345678 2010", false, true, 1, 9},
{"millisecond:: comma separator", "Mon Jan _2 15:04:05,000 2006", "Thu Feb 4 21:00:57.012 2010", false, true, 1, 3},
{"microsecond:: comma separator", "Mon Jan _2 15:04:05,000000 2006", "Thu Feb 4 21:00:57.012345 2010", false, true, 1, 6},
{"nanosecond:: comma separator", "Mon Jan _2 15:04:05,000000000 2006", "Thu Feb 4 21:00:57.012345678 2010", false, true, 1, 9},

// Leading zeros in other places should not be taken as fractional seconds.
{"zero1", "2006.01.02.15.04.05.0", "2010.02.04.21.00.57.0", false, false, 1, 1},
{"zero2", "2006.01.02.15.04.05.00", "2010.02.04.21.00.57.01", false, false, 1, 2},
Expand All @@ -222,12 +226,20 @@ var parseTests = []ParseTest{
// Accept any number of fractional second digits (including none) for .999...
// In Go 1, .999... was completely ignored in the format, meaning the first two
// cases would succeed, but the next four would not. Go 1.1 accepts all six.
// decimal "." separator.
{"", "2006-01-02 15:04:05.9999 -0700 MST", "2010-02-04 21:00:57 -0800 PST", true, false, 1, 0},
{"", "2006-01-02 15:04:05.999999999 -0700 MST", "2010-02-04 21:00:57 -0800 PST", true, false, 1, 0},
{"", "2006-01-02 15:04:05.9999 -0700 MST", "2010-02-04 21:00:57.0123 -0800 PST", true, false, 1, 4},
{"", "2006-01-02 15:04:05.999999999 -0700 MST", "2010-02-04 21:00:57.0123 -0800 PST", true, false, 1, 4},
{"", "2006-01-02 15:04:05.9999 -0700 MST", "2010-02-04 21:00:57.012345678 -0800 PST", true, false, 1, 9},
{"", "2006-01-02 15:04:05.999999999 -0700 MST", "2010-02-04 21:00:57.012345678 -0800 PST", true, false, 1, 9},
// comma "," separator.
{"", "2006-01-02 15:04:05,9999 -0700 MST", "2010-02-04 21:00:57 -0800 PST", true, false, 1, 0},
{"", "2006-01-02 15:04:05,999999999 -0700 MST", "2010-02-04 21:00:57 -0800 PST", true, false, 1, 0},
{"", "2006-01-02 15:04:05,9999 -0700 MST", "2010-02-04 21:00:57.0123 -0800 PST", true, false, 1, 4},
{"", "2006-01-02 15:04:05,999999999 -0700 MST", "2010-02-04 21:00:57.0123 -0800 PST", true, false, 1, 4},
{"", "2006-01-02 15:04:05,9999 -0700 MST", "2010-02-04 21:00:57.012345678 -0800 PST", true, false, 1, 9},
{"", "2006-01-02 15:04:05,999999999 -0700 MST", "2010-02-04 21:00:57.012345678 -0800 PST", true, false, 1, 9},

// issue 4502.
{"", StampNano, "Feb 4 21:00:57.012345678", false, false, -1, 9},
Expand Down

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