From 260991ad5f1cd73ff9f993bb389ac6d7e56fb509 Mon Sep 17 00:00:00 2001
From: Mike Samuel <mikesamuel@gmail.com>
Date: Tue, 27 Sep 2011 22:08:14 -0700
Subject: [PATCH] exp/template/html: do not escape the RHS of assignments

In

  {{$x := . | foo}}
  {{$x}}

the first action is a variable assignment that contributes
nothing to the output while the first is a use that needs
to be escaped.

This CL fixes escapeAction to distinguish assignments from
interpolations and to only modify interpolations.

R=nigeltao, r
CC=golang-dev
https://golang.org/cl/5143048
---
 src/pkg/exp/template/html/escape.go      |  4 ++++
 src/pkg/exp/template/html/escape_test.go | 12 +++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/pkg/exp/template/html/escape.go b/src/pkg/exp/template/html/escape.go
index 5ea819fc50..bb286c8844 100644
--- a/src/pkg/exp/template/html/escape.go
+++ b/src/pkg/exp/template/html/escape.go
@@ -153,6 +153,10 @@ func (e *escaper) escape(c context, n parse.Node) context {
 
 // escapeAction escapes an action template node.
 func (e *escaper) escapeAction(c context, n *parse.ActionNode) context {
+	if len(n.Pipe.Decl) != 0 {
+		// A local variable assignment, not an interpolation.
+		return c
+	}
 	c = nudge(c)
 	s := make([]string, 0, 3)
 	switch c.state {
diff --git a/src/pkg/exp/template/html/escape_test.go b/src/pkg/exp/template/html/escape_test.go
index d251cdb9a3..c464459165 100644
--- a/src/pkg/exp/template/html/escape_test.go
+++ b/src/pkg/exp/template/html/escape_test.go
@@ -68,10 +68,20 @@ func TestEscape(t *testing.T) {
 			"&lt;Goodbye&gt;!",
 		},
 		{
-			"overescaping",
+			"overescaping1",
 			"Hello, {{.C | html}}!",
 			"Hello, &lt;Cincinatti&gt;!",
 		},
+		{
+			"overescaping2",
+			"Hello, {{html .C}}!",
+			"Hello, &lt;Cincinatti&gt;!",
+		},
+		{
+			"overescaping3",
+			"{{with .C}}{{$msg := .}}Hello, {{$msg}}!{{end}}",
+			"Hello, &lt;Cincinatti&gt;!",
+		},
 		{
 			"assignment",
 			"{{if $x := .H}}{{$x}}{{end}}",