1 files changed, 41 insertions, 8 deletions
diff --git a/src/pkg/go/doc/comment.go b/src/pkg/go/doc/comment.go
index 5c8c43e0c..f414ca409 100644
--- a/src/pkg/go/doc/comment.go
+++ b/src/pkg/go/doc/comment.go
@@ -45,13 +45,13 @@ func commentEscape(w io.Writer, text string, nice bool) {
 
 const (
 	// Regexp for Go identifiers
-	identRx = `[a-zA-Z_][a-zA-Z_0-9]*` // TODO(gri) ASCII only for now - fix this
+	identRx = `[\pL_][\pL_0-9]*`
 
 	// Regexp for URLs
-	protocol = `(https?|ftp|file|gopher|mailto|news|nntp|telnet|wais|prospero):`
+	protocol = `https?|ftp|file|gopher|mailto|news|nntp|telnet|wais|prospero`
 	hostPart = `[a-zA-Z0-9_@\-]+`
-	filePart = `[a-zA-Z0-9_?%#~&/\-+=]+`
-	urlRx    = protocol + `//` + // http://
+	filePart = `[a-zA-Z0-9_?%#~&/\-+=()]+` // parentheses may not be matching; see pairedParensPrefixLen
+	urlRx    = `(` + protocol + `)://` +   // http://
 		hostPart + `([.:]` + hostPart + `)*/?` + // //www.google.com:8080/
 		filePart + `([:.,]` + filePart + `)*`
 )
@@ -73,6 +73,29 @@ var (
 	html_endh   = []byte("</h3>\n")
 )
 
+// pairedParensPrefixLen returns the length of the longest prefix of s containing paired parentheses.
+func pairedParensPrefixLen(s string) int {
+	parens := 0
+	l := len(s)
+	for i, ch := range s {
+		switch ch {
+		case '(':
+			if parens == 0 {
+				l = i
+			}
+			parens++
+		case ')':
+			parens--
+			if parens == 0 {
+				l = len(s)
+			} else if parens < 0 {
+				return i
+			}
+		}
+	}
+	return l
+}
+
 // Emphasize and escape a line of text for HTML. URLs are converted into links;
 // if the URL also appears in the words map, the link is taken from the map (if
 // the corresponding map value is the empty string, the URL is not converted
@@ -92,18 +115,26 @@ func emphasize(w io.Writer, line string, words map[string]string, nice bool) {
 		// write text before match
 		commentEscape(w, line[0:m[0]], nice)
 
-		// analyze match
+		// adjust match if necessary
 		match := line[m[0]:m[1]]
+		if n := pairedParensPrefixLen(match); n < len(match) {
+			// match contains unpaired parentheses (rare);
+			// redo matching with shortened line for correct indices
+			m = matchRx.FindStringSubmatchIndex(line[:m[0]+n])
+			match = match[:n]
+		}
+
+		// analyze match
 		url := ""
 		italics := false
 		if words != nil {
-			url, italics = words[string(match)]
+			url, italics = words[match]
 		}
 		if m[2] >= 0 {
 			// match against first parenthesized sub-regexp; must be match against urlRx
 			if !italics {
 				// no alternative URL in words list, use match instead
-				url = string(match)
+				url = match
 			}
 			italics = false // don't italicize URLs
 		}
@@ -392,7 +423,9 @@ func ToText(w io.Writer, text string, indent, preIndent string, width int) {
 		case opPre:
 			w.Write(nl)
 			for _, line := range b.lines {
-				if !isBlank(line) {
+				if isBlank(line) {
+					w.Write([]byte("\n"))
+				} else {
 					w.Write([]byte(preIndent))
 					w.Write([]byte(line))
 				}