time: properly quote strings containing quotes and backslashes

Fixes #45391

Change-Id: I43ea597f6a9596a621ae7b63eb05440d5b9e2d8f
Reviewed-on: https://go-review.googlesource.com/c/go/+/307192
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Go Bot <gobot@golang.org>

src/time/export_test.go

@@ -129,3 +129,5 @@ var StdChunkNames = map[int]string{
 	stdFracSecond9 | 8<<stdArgShift: ".99999999",
 	stdFracSecond9 | 9<<stdArgShift: ".999999999",
 }
+
+var Quote = quote

src/time/format.go

@@ -689,7 +689,16 @@ type ParseError struct {
 }
 
 func quote(s string) string {
-	return "\"" + s + "\""
+	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 = append(buf, string(c)...)
+	}
+	buf = append(buf, '"')
+	return string(buf)
 }
 
 // Error returns the string representation of a ParseError.

src/time/format_test.go

@@ -563,6 +563,10 @@ var parseErrorTests = []ParseErrorTest{
 	// invalid or mismatched day-of-year
 	{"Jan _2 002 2006", "Feb  4 034 2006", "day-of-year does not match day"},
 	{"Jan _2 002 2006", "Feb  4 004 2006", "day-of-year does not match month"},
+
+	// issue 45391.
+	{`"2006-01-02T15:04:05Z07:00"`, "0", `parsing time "0" as "\"2006-01-02T15:04:05Z07:00\"": cannot parse "0" as "\""`},
+	{RFC3339, "\"", `parsing time "\"" as "2006-01-02T15:04:05Z07:00": cannot parse "\"" as "2006"`},
 }
 
 func TestParseErrors(t *testing.T) {
@@ -782,3 +786,21 @@ func TestParseYday(t *testing.T) {
 		}
 	}
 }
+
+// Issue 45391.
+func TestQuote(t *testing.T) {
+	tests := []struct {
+		s, want string
+	}{
+		{`"`, `"\""`},
+		{`abc"xyz"`, `"abc\"xyz\""`},
+		{"", `""`},
+		{"abc", `"abc"`},
+	}
+	for _, tt := range tests {
+		if q := Quote(tt.s); q != tt.want {
+			t.Errorf("Quote(%q) = %q, want %q", tt.s, q, tt.want)
+		}
+	}
+
+}