time: quote original value in errors returned by ParseDuration

Quote original values passed as substring of ParseError.Message.
Improves the user experience of ParseDuration by making it
quote its original argument, for example:

   _, err := time.ParseDuration("for breakfast")
 will now produce an error, which when printed out is:

  time: invalid duration "for breakfast"
 instead of:

  time: invalid duration for breakfast

Adapt test cases for format.Parse and format.ParseDuration.

Fixes #38295

Change-Id: Ife322c8f3c859e1e4e8dd546d4cf0d519b4bfa81
Reviewed-on: https://go-review.googlesource.com/c/go/+/227878
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

4 files changed, 90 insertions, 73 deletions

diff --git a/src/time/example_test.go b/src/time/example_test.go
index f272ee44df..15811a62d3 100644
--- a/src/time/example_test.go
+++ b/src/time/example_test.go
@@ -379,7 +379,7 @@ func ExampleParse() {
 	// 2013-02-03 00:00:00 +0000 UTC
 	// 2006-01-02 15:04:05 +0000 UTC
 	// 2006-01-02 15:04:05 +0700 +0700
-	// error parsing time "2006-01-02T15:04:05Z07:00": extra text: 07:00
+	// error parsing time "2006-01-02T15:04:05Z07:00": extra text: "07:00"
 }
 
 func ExampleParseInLocation() {
diff --git a/src/time/format.go b/src/time/format.go
index 899b6a40b0..b74108f0e7 100644
--- a/src/time/format.go
+++ b/src/time/format.go
@@ -856,7 +856,7 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
 		}
 		if std == 0 {
 			if len(value) != 0 {
-				return Time{}, &ParseError{alayout, avalue, "", value, ": extra text: " + value}
+				return Time{}, &ParseError{alayout, avalue, "", value, ": extra text: " + quote(value)}
 			}
 			break
 		}
@@ -1390,7 +1390,7 @@ func ParseDuration(s string) (Duration, error) {
 		return 0, nil
 	}
 	if s == "" {
-		return 0, errors.New("time: invalid duration " + orig)
+		return 0, errors.New("time: invalid duration " + quote(orig))
 	}
 	for s != "" {
 		var (
@@ -1402,13 +1402,13 @@ func ParseDuration(s string) (Duration, error) {
 
 		// The next character must be [0-9.]
 		if !(s[0] == '.' || '0' <= s[0] && s[0] <= '9') {
-			return 0, errors.New("time: invalid duration " + orig)
+			return 0, errors.New("time: invalid duration " + quote(orig))
 		}
 		// Consume [0-9]*
 		pl := len(s)
 		v, s, err = leadingInt(s)
 		if err != nil {
-			return 0, errors.New("time: invalid duration " + orig)
+			return 0, errors.New("time: invalid duration " + quote(orig))
 		}
 		pre := pl != len(s) // whether we consumed anything before a period
 
@@ -1422,7 +1422,7 @@ func ParseDuration(s string) (Duration, error) {
 		}
 		if !pre && !post {
 			// no digits (e.g. ".s" or "-.s")
-			return 0, errors.New("time: invalid duration " + orig)
+			return 0, errors.New("time: invalid duration " + quote(orig))
 		}
 
 		// Consume unit.
@@ -1434,17 +1434,17 @@ func ParseDuration(s string) (Duration, error) {
 			}
 		}
 		if i == 0 {
-			return 0, errors.New("time: missing unit in duration " + orig)
+			return 0, errors.New("time: missing unit in duration " + quote(orig))
 		}
 		u := s[:i]
 		s = s[i:]
 		unit, ok := unitMap[u]
 		if !ok {
-			return 0, errors.New("time: unknown unit " + u + " in duration " + orig)
+			return 0, errors.New("time: unknown unit " + quote(u) + " in duration " + quote(orig))
 		}
 		if v > (1<<63-1)/unit {
 			// overflow
-			return 0, errors.New("time: invalid duration " + orig)
+			return 0, errors.New("time: invalid duration " + quote(orig))
 		}
 		v *= unit
 		if f > 0 {
@@ -1453,13 +1453,13 @@ func ParseDuration(s string) (Duration, error) {
 			v += int64(float64(f) * (float64(unit) / scale))
 			if v < 0 {
 				// overflow
-				return 0, errors.New("time: invalid duration " + orig)
+				return 0, errors.New("time: invalid duration " + quote(orig))
 			}
 		}
 		d += v
 		if d < 0 {
 			// overflow
-			return 0, errors.New("time: invalid duration " + orig)
+			return 0, errors.New("time: invalid duration " + quote(orig))
 		}
 	}
 
diff --git a/src/time/format_test.go b/src/time/format_test.go
index a030242e6a..4574d20319 100644
--- a/src/time/format_test.go
+++ b/src/time/format_test.go
@@ -536,12 +536,12 @@ var parseErrorTests = []ParseErrorTest{
 	{"Mon Jan _2 15:04:05.000 2006", "Thu Feb  4 23:00:59.-123 2010", "fractional second out of range"},
 	// issue 4502. StampNano requires exactly 9 digits of precision.
 	{StampNano, "Dec  7 11:22:01.000000", `cannot parse ".000000" as ".000000000"`},
-	{StampNano, "Dec  7 11:22:01.0000000000", "extra text: 0"},
+	{StampNano, "Dec  7 11:22:01.0000000000", `extra text: "0"`},
 	// issue 4493. Helpful errors.
-	{RFC3339, "2006-01-02T15:04:05Z07:00", `parsing time "2006-01-02T15:04:05Z07:00": extra text: 07:00`},
+	{RFC3339, "2006-01-02T15:04:05Z07:00", `parsing time "2006-01-02T15:04:05Z07:00": extra text: "07:00"`},
 	{RFC3339, "2006-01-02T15:04_abc", `parsing time "2006-01-02T15:04_abc" as "2006-01-02T15:04:05Z07:00": cannot parse "_abc" as ":"`},
 	{RFC3339, "2006-01-02T15:04:05_abc", `parsing time "2006-01-02T15:04:05_abc" as "2006-01-02T15:04:05Z07:00": cannot parse "_abc" as "Z07:00"`},
-	{RFC3339, "2006-01-02T15:04:05Z_abc", `parsing time "2006-01-02T15:04:05Z_abc": extra text: _abc`},
+	{RFC3339, "2006-01-02T15:04:05Z_abc", `parsing time "2006-01-02T15:04:05Z_abc": extra text: "_abc"`},
 	// invalid second followed by optional fractional seconds
 	{RFC3339, "2010-02-04T21:00:67.012345678-08:00", "second out of range"},
 	// issue 21113
diff --git a/src/time/time_test.go b/src/time/time_test.go
index ffbf92acbc..ab96d67aa9 100644
--- a/src/time/time_test.go
+++ b/src/time/time_test.go
@@ -810,86 +810,103 @@ func TestNotJSONEncodableTime(t *testing.T) {
 
 var parseDurationTests = []struct {
 	in   string
-	ok   bool
 	want Duration
 }{
 	// simple
-	{"0", true, 0},
-	{"5s", true, 5 * Second},
-	{"30s", true, 30 * Second},
-	{"1478s", true, 1478 * Second},
+	{"0", 0},
+	{"5s", 5 * Second},
+	{"30s", 30 * Second},
+	{"1478s", 1478 * Second},
 	// sign
-	{"-5s", true, -5 * Second},
-	{"+5s", true, 5 * Second},
-	{"-0", true, 0},
-	{"+0", true, 0},
+	{"-5s", -5 * Second},
+	{"+5s", 5 * Second},
+	{"-0", 0},
+	{"+0", 0},
 	// decimal
-	{"5.0s", true, 5 * Second},
-	{"5.6s", true, 5*Second + 600*Millisecond},
-	{"5.s", true, 5 * Second},
-	{".5s", true, 500 * Millisecond},
-	{"1.0s", true, 1 * Second},
-	{"1.00s", true, 1 * Second},
-	{"1.004s", true, 1*Second + 4*Millisecond},
-	{"1.0040s", true, 1*Second + 4*Millisecond},
-	{"100.00100s", true, 100*Second + 1*Millisecond},
+	{"5.0s", 5 * Second},
+	{"5.6s", 5*Second + 600*Millisecond},
+	{"5.s", 5 * Second},
+	{".5s", 500 * Millisecond},
+	{"1.0s", 1 * Second},
+	{"1.00s", 1 * Second},
+	{"1.004s", 1*Second + 4*Millisecond},
+	{"1.0040s", 1*Second + 4*Millisecond},
+	{"100.00100s", 100*Second + 1*Millisecond},
 	// different units
-	{"10ns", true, 10 * Nanosecond},
-	{"11us", true, 11 * Microsecond},
-	{"12µs", true, 12 * Microsecond}, // U+00B5
-	{"12μs", true, 12 * Microsecond}, // U+03BC
-	{"13ms", true, 13 * Millisecond},
-	{"14s", true, 14 * Second},
-	{"15m", true, 15 * Minute},
-	{"16h", true, 16 * Hour},
+	{"10ns", 10 * Nanosecond},
+	{"11us", 11 * Microsecond},
+	{"12µs", 12 * Microsecond}, // U+00B5
+	{"12μs", 12 * Microsecond}, // U+03BC
+	{"13ms", 13 * Millisecond},
+	{"14s", 14 * Second},
+	{"15m", 15 * Minute},
+	{"16h", 16 * Hour},
 	// composite durations
-	{"3h30m", true, 3*Hour + 30*Minute},
-	{"10.5s4m", true, 4*Minute + 10*Second + 500*Millisecond},
-	{"-2m3.4s", true, -(2*Minute + 3*Second + 400*Millisecond)},
-	{"1h2m3s4ms5us6ns", true, 1*Hour + 2*Minute + 3*Second + 4*Millisecond + 5*Microsecond + 6*Nanosecond},
-	{"39h9m14.425s", true, 39*Hour + 9*Minute + 14*Second + 425*Millisecond},
+	{"3h30m", 3*Hour + 30*Minute},
+	{"10.5s4m", 4*Minute + 10*Second + 500*Millisecond},
+	{"-2m3.4s", -(2*Minute + 3*Second + 400*Millisecond)},
+	{"1h2m3s4ms5us6ns", 1*Hour + 2*Minute + 3*Second + 4*Millisecond + 5*Microsecond + 6*Nanosecond},
+	{"39h9m14.425s", 39*Hour + 9*Minute + 14*Second + 425*Millisecond},
 	// large value
-	{"52763797000ns", true, 52763797000 * Nanosecond},
+	{"52763797000ns", 52763797000 * Nanosecond},
 	// more than 9 digits after decimal point, see https://golang.org/issue/6617
-	{"0.3333333333333333333h", true, 20 * Minute},
+	{"0.3333333333333333333h", 20 * Minute},
 	// 9007199254740993 = 1<<53+1 cannot be stored precisely in a float64
-	{"9007199254740993ns", true, (1<<53 + 1) * Nanosecond},
+	{"9007199254740993ns", (1<<53 + 1) * Nanosecond},
 	// largest duration that can be represented by int64 in nanoseconds
-	{"9223372036854775807ns", true, (1<<63 - 1) * Nanosecond},
-	{"9223372036854775.807us", true, (1<<63 - 1) * Nanosecond},
-	{"9223372036s854ms775us807ns", true, (1<<63 - 1) * Nanosecond},
+	{"9223372036854775807ns", (1<<63 - 1) * Nanosecond},
+	{"9223372036854775.807us", (1<<63 - 1) * Nanosecond},
+	{"9223372036s854ms775us807ns", (1<<63 - 1) * Nanosecond},
 	// large negative value
-	{"-9223372036854775807ns", true, -1<<63 + 1*Nanosecond},
+	{"-9223372036854775807ns", -1<<63 + 1*Nanosecond},
 	// huge string; issue 15011.
-	{"0.100000000000000000000h", true, 6 * Minute},
+	{"0.100000000000000000000h", 6 * Minute},
 	// This value tests the first overflow check in leadingFraction.
-	{"0.830103483285477580700h", true, 49*Minute + 48*Second + 372539827*Nanosecond},
-
-	// errors
-	{"", false, 0},
-	{"3", false, 0},
-	{"-", false, 0},
-	{"s", false, 0},
-	{".", false, 0},
-	{"-.", false, 0},
-	{".s", false, 0},
-	{"+.s", false, 0},
-	{"3000000h", false, 0},                  // overflow
-	{"9223372036854775808ns", false, 0},     // overflow
-	{"9223372036854775.808us", false, 0},    // overflow
-	{"9223372036854ms775us808ns", false, 0}, // overflow
-	// largest negative value of type int64 in nanoseconds should fail
-	// see https://go-review.googlesource.com/#/c/2461/
-	{"-9223372036854775808ns", false, 0},
+	{"0.830103483285477580700h", 49*Minute + 48*Second + 372539827*Nanosecond},
 }
 
 func TestParseDuration(t *testing.T) {
 	for _, tc := range parseDurationTests {
 		d, err := ParseDuration(tc.in)
-		if tc.ok && (err != nil || d != tc.want) {
+		if err != nil || d != tc.want {
 			t.Errorf("ParseDuration(%q) = %v, %v, want %v, nil", tc.in, d, err, tc.want)
-		} else if !tc.ok && err == nil {
+		}
+	}
+}
+
+var parseDurationErrorTests = []struct {
+	in     string
+	expect string
+}{
+	// invalid
+	{"", `""`},
+	{"3", `"3"`},
+	{"-", `"-"`},
+	{"s", `"s"`},
+	{".", `"."`},
+	{"-.", `"-."`},
+	{".s", `".s"`},
+	{"+.s", `"+.s"`},
+	{"1d", `"1d"`},
+	// overflow
+	{"9223372036854775810ns", `"9223372036854775810ns"`},
+	{"9223372036854775808ns", `"9223372036854775808ns"`},
+	// largest negative value of type int64 in nanoseconds should fail
+	// see https://go-review.googlesource.com/#/c/2461/
+	{"-9223372036854775808ns", `"-9223372036854775808ns"`},
+	{"9223372036854776us", `"9223372036854776us"`},
+	{"3000000h", `"3000000h"`},
+	{"9223372036854775.808us", `"9223372036854775.808us"`},
+	{"9223372036854ms775us808ns", `"9223372036854ms775us808ns"`},
+}
+
+func TestParseDurationErrors(t *testing.T) {
+	for _, tc := range parseDurationErrorTests {
+		_, err := ParseDuration(tc.in)
+		if err == nil {
 			t.Errorf("ParseDuration(%q) = _, nil, want _, non-nil", tc.in)
+		} else if !strings.Contains(err.Error(), tc.expect) {
+			t.Errorf("ParseDuration(%q) = _, %q, error does not contain %q", tc.in, err, tc.expect)
 		}
 	}
 }