From bb09f8a29b04b8fe4465d0b5d92f164979ee9213 Mon Sep 17 00:00:00 2001 From: Kevin Burke Date: Thu, 25 Mar 2021 12:33:35 -0700 Subject: [PATCH] time: make time.Time print a valid Go string with %#v Previously calling fmt.Sprintf("%#v", t) on a time.Time value would yield a result like: time.Time{wall:0x0, ext:63724924180, loc:(*time.Location)(nil)} which does not compile when embedded in a Go program, and does not tell you what value is represented at a glance. This change adds a GoString method that returns much more legible output: "time.Date(2009, time.February, 5, 5, 0, 57, 12345600, time.UTC)" which gives you more information about the time.Time and also can be usefully embedded in a Go program without additional work. Update Quote() to hex escape non-ASCII characters (copying logic from strconv), which makes it safer to embed them in the output of GoString(). Fixes #39034. Change-Id: Ic985bafe4e556f64e82223c643f65143c9a45c3b Reviewed-on: https://go-review.googlesource.com/c/go/+/267017 Reviewed-by: Emmanuel Odeke Reviewed-by: Ian Lance Taylor Run-TryBot: Emmanuel Odeke --- doc/go1.17.html | 9 +++++ src/time/format.go | 85 ++++++++++++++++++++++++++++++++++++++--- src/time/format_test.go | 30 ++++++++++++++- 3 files changed, 117 insertions(+), 7 deletions(-) diff --git a/doc/go1.17.html b/doc/go1.17.html index b670d1b149..0521f9fd91 100644 --- a/doc/go1.17.html +++ b/doc/go1.17.html @@ -205,6 +205,15 @@ that can be used to pass values between C and Go safely. See

+
time
+
+

+ time.Time now has a GoString + method that will return a more useful value for times when printed with + the "%#v" format specifier in the fmt package. +

+
+

TODO: complete this section

diff --git a/src/time/format.go b/src/time/format.go index 9624752fb4..f6dc8ee621 100644 --- a/src/time/format.go +++ b/src/time/format.go @@ -477,6 +477,60 @@ func (t Time) String() string { return s } +// GoString implements fmt.GoStringer and formats t to be printed in Go source +// code. +func (t Time) GoString() string { + buf := []byte("time.Date(") + buf = appendInt(buf, t.Year(), 0) + month := t.Month() + if January <= month && month <= December { + buf = append(buf, ", time."...) + buf = append(buf, t.Month().String()...) + } else { + // It's difficult to construct a time.Time with a date outside the + // standard range but we might as well try to handle the case. + buf = appendInt(buf, int(month), 0) + } + buf = append(buf, ", "...) + buf = appendInt(buf, t.Day(), 0) + buf = append(buf, ", "...) + buf = appendInt(buf, t.Hour(), 0) + buf = append(buf, ", "...) + buf = appendInt(buf, t.Minute(), 0) + buf = append(buf, ", "...) + buf = appendInt(buf, t.Second(), 0) + buf = append(buf, ", "...) + buf = appendInt(buf, t.Nanosecond(), 0) + buf = append(buf, ", "...) + switch loc := t.Location(); loc { + case UTC, nil: + buf = append(buf, "time.UTC"...) + case Local: + buf = append(buf, "time.Local"...) + default: + // there are several options for how we could display this, none of + // which are great: + // + // - use Location(loc.name), which is not technically valid syntax + // - use LoadLocation(loc.name), which will cause a syntax error when + // embedded and also would require us to escape the string without + // importing fmt or strconv + // - try to use FixedZone, which would also require escaping the name + // and would represent e.g. "America/Los_Angeles" daylight saving time + // shifts inaccurately + // - use the pointer format, which is no worse than you'd get with the + // old fmt.Sprintf("%#v", t) format. + // + // Of these, Location(loc.name) is the least disruptive. This is an edge + // case we hope not to hit too often. + buf = append(buf, `time.Location(`...) + buf = append(buf, []byte(quote(loc.name))...) + buf = append(buf, `)`...) + } + buf = append(buf, ')') + return string(buf) +} + // Format returns a textual representation of the time value formatted // according to layout, which defines the format by showing how the reference // time, defined to be @@ -688,14 +742,33 @@ type ParseError struct { Message string } +// These are borrowed from unicode/utf8 and strconv and replicate behavior in +// that package, since we can't take a dependency on either. +const runeSelf = 0x80 +const lowerhex = "0123456789abcdef" + func quote(s string) string { - buf := make([]byte, 0, len(s)+2) // +2 for surrounding quotes - buf = append(buf, '"') - for _, c := range s { - if c == '"' || c == '\\' { - buf = append(buf, '\\') + buf := make([]byte, 1, len(s)+2) // slice will be at least len(s) + quotes + buf[0] = '"' + for i, c := range s { + if c >= runeSelf || c < ' ' { + // This means you are asking us to parse a time.Duration or + // time.Location with unprintable or non-ASCII characters in it. + // We don't expect to hit this case very often. We could try to + // reproduce strconv.Quote's behavior with full fidelity but + // given how rarely we expect to hit these edge cases, speed and + // conciseness are better. + for j := 0; j < len(string(c)) && j < len(s); j++ { + buf = append(buf, `\x`...) + buf = append(buf, lowerhex[s[i+j]>>4]) + buf = append(buf, lowerhex[s[i+j]&0xF]) + } + } else { + if c == '"' || c == '\\' { + buf = append(buf, '\\') + } + buf = append(buf, string(c)...) } - buf = append(buf, string(c)...) } buf = append(buf, '"') return string(buf) diff --git a/src/time/format_test.go b/src/time/format_test.go index 09d3f842e3..1af41e2dfb 100644 --- a/src/time/format_test.go +++ b/src/time/format_test.go @@ -129,6 +129,31 @@ func TestFormat(t *testing.T) { } } +var goStringTests = []struct { + in Time + want string +}{ + {Date(2009, February, 5, 5, 0, 57, 12345600, UTC), + "time.Date(2009, time.February, 5, 5, 0, 57, 12345600, time.UTC)"}, + {Date(2009, February, 5, 5, 0, 57, 12345600, Local), + "time.Date(2009, time.February, 5, 5, 0, 57, 12345600, time.Local)"}, + {Date(2009, February, 5, 5, 0, 57, 12345600, FixedZone("Europe/Berlin", 3*60*60)), + `time.Date(2009, time.February, 5, 5, 0, 57, 12345600, time.Location("Europe/Berlin"))`, + }, + {Date(2009, February, 5, 5, 0, 57, 12345600, FixedZone("Non-ASCII character ⏰", 3*60*60)), + `time.Date(2009, time.February, 5, 5, 0, 57, 12345600, time.Location("Non-ASCII character \xe2\x8f\xb0"))`, + }, +} + +func TestGoString(t *testing.T) { + // The numeric time represents Thu Feb 4 21:00:57.012345600 PST 2009 + for _, tt := range goStringTests { + if tt.in.GoString() != tt.want { + t.Errorf("GoString (%q): got %q want %q", tt.in, tt.in.GoString(), tt.want) + } + } +} + // issue 12440. func TestFormatSingleDigits(t *testing.T) { time := Date(2001, 2, 3, 4, 5, 6, 700000000, UTC) @@ -796,10 +821,13 @@ func TestQuote(t *testing.T) { {`abc"xyz"`, `"abc\"xyz\""`}, {"", `""`}, {"abc", `"abc"`}, + {`☺`, `"\xe2\x98\xba"`}, + {`☺ hello ☺ hello`, `"\xe2\x98\xba hello \xe2\x98\xba hello"`}, + {"\x04", `"\x04"`}, } for _, tt := range tests { if q := Quote(tt.s); q != tt.want { - t.Errorf("Quote(%q) = %q, want %q", tt.s, q, tt.want) + t.Errorf("Quote(%q) = got %q, want %q", tt.s, q, tt.want) } } -- 2.50.0