exp/template/html: fix bug in cssEscaper

cssEscaper escapes using the CSS convention: `\` + hex + optional-space

It outputs the space when the escape could be followed by
a hex digit to distinguish a "\na" from "\u00aa".

It did not output a space when the escape is followed by a space
character so did not distinguish "\n " from "\n".

Currently when doing lookahead, it does not distinguish spaces that
will be escaped later by the same function from ones that will not.
This is correct but suboptimal.

R=nigeltao
CC=golang-dev
https://golang.org/cl/5306042

diff --git a/src/pkg/exp/template/html/css.go b/src/pkg/exp/template/html/css.go
index d881328c93cb2e78aa0874b0616f4adcb299ba8c..c22ec6df0d07aa6fdf5b6d5a0a74257a47d8cc2e 100644 (file)
--- a/src/pkg/exp/template/html/css.go
+++ b/src/pkg/exp/template/html/css.go
@@ -144,6 +144,15 @@ func skipCSSSpace(c []byte) []byte {
        return c
 }
 
+// isCSSSpace returns whether b is a CSS space char as defined in wc.
+func isCSSSpace(b byte) bool {
+       switch b {
+       case '\t', '\n', '\f', '\r', ' ':
+               return true
+       }
+       return false
+}
+
 // cssEscaper escapes HTML and CSS special characters using \<hex>+ escapes.
 func cssEscaper(args ...interface{}) string {
        s, _ := stringify(args...)
@@ -198,7 +207,7 @@ func cssEscaper(args ...interface{}) string {
                b.WriteString(s[written:i])
                b.WriteString(repl)
                written = i + utf8.RuneLen(r)
-               if repl != `\\` && (written == len(s) || isHex(s[written])) {
+               if repl != `\\` && (written == len(s) || isHex(s[written]) || isCSSSpace(s[written])) {
                        b.WriteByte(' ')
                }
        }

diff --git a/src/pkg/exp/template/html/css_test.go b/src/pkg/exp/template/html/css_test.go
index 5ba3e77bb365710141d928d8c64ec9abfe312d9d..5f633e89442afa955a409ff054b559a1872d730c 100644 (file)
--- a/src/pkg/exp/template/html/css_test.go
+++ b/src/pkg/exp/template/html/css_test.go
@@ -100,9 +100,13 @@ func TestDecodeCSS(t *testing.T) {
                },
        }
        for _, test := range tests {
-               got := string(decodeCSS([]byte(test.css)))
-               if got != test.want {
-                       t.Errorf("%q: want\n\t%q\nbut got\n\t%q", test.css, test.want, got)
+               got1 := string(decodeCSS([]byte(test.css)))
+               if got1 != test.want {
+                       t.Errorf("%q: want\n\t%q\nbut got\n\t%q", test.css, test.want, got1)
+               }
+               recoded := cssEscaper(got1)
+               if got2 := string(decodeCSS([]byte(recoded))); got2 != test.want {
+                       t.Errorf("%q: escape & decode not dual for %q", test.css, recoded)
                }
        }
 }
@@ -156,7 +160,7 @@ func TestCSSEscaper(t *testing.T) {
                "\u00A0\u0100\u2028\u2029\ufeff\U0001D11E")
 
        want := ("\\0\x01\x02\x03\x04\x05\x06\x07" +
-               "\x08\\9\\a\x0b\\c\\d\x0E\x0F" +
+               "\x08\\9 \\a\x0b\\c \\d\x0E\x0F" +
                "\x10\x11\x12\x13\x14\x15\x16\x17" +
                "\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" +
                ` !\22#$%\26\27\28\29*\2b,-.\2f ` +