exp/template: url filter.

R=r
CC=golang-dev
https://golang.org/cl/4837063

src/pkg/exp/template/doc.go

@@ -244,6 +244,9 @@ Predefined global functions are named as follows.
 		An alias for fmt.Sprintf
 	println
 		An alias for fmt.Sprintln
+	url
+		Returns the escaped value of the textual representation of
+		its arguments in a form suitable for embedding in a URL.
 
 The boolean functions take any zero value to be false and a non-zero value to
 be true.

src/pkg/exp/template/exec_test.go

@@ -283,6 +283,9 @@ var execTests = []execTest{
 	// JavaScript.
 	{"js", `{{js .}}`, `It\'d be nice.`, `It'd be nice.`, true},
 
+	// URL.
+	{"url", `{{"http://www.example.org/"|url}}`, "http%3A%2F%2Fwww.example.org%2F", nil, true},
+
 	// Booleans
 	{"not", "{{not true}} {{not false}}", "false true", nil, true},
 	{"and", "{{and false 0}} {{and 1 0}} {{and 0 true}} {{and 1 1}}", "false 0 0 1", nil, true},

src/pkg/exp/template/funcs.go

@@ -7,6 +7,7 @@ package template
 import (
 	"bytes"
 	"fmt"
+	"http"
 	"io"
 	"os"
 	"reflect"
@@ -31,6 +32,7 @@ var funcs = map[string]reflect.Value{
 	"print":   reflect.ValueOf(fmt.Sprint),
 	"printf":  reflect.ValueOf(fmt.Sprintf),
 	"println": reflect.ValueOf(fmt.Sprintln),
+	"url":     reflect.ValueOf(URLEscaper),
 }
 
 // addFuncs adds to values the functions in funcs, converting them to reflect.Values.
@@ -318,3 +320,16 @@ func JSEscaper(args ...interface{}) string {
 	}
 	return JSEscapeString(s)
 }
+
+// URLEscaper returns the escaped value of the textual representation of its
+// arguments in a form suitable for embedding in a URL.
+func URLEscaper(args ...interface{}) string {
+	s, ok := "", false
+	if len(args) == 1 {
+		s, ok = args[0].(string)
+	}
+	if !ok {
+		s = fmt.Sprint(args...)
+	}
+	return http.URLEscape(s)
+}