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html/template: fix Clone so that t.Lookup(t.Name()) yields t

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Template.escape makes the assumption that t.Lookup(t.Name()) is t
(escapeTemplate looks up the associated template by name and sets
escapeErr appropriately).

This assumption did not hold for a Cloned template, because the template
associated with t.Name() was a second copy of the original.

Add a test for the assumption that t.Lookup(t.Name()) == t.

One effect of this broken assumption was #16101: parallel Executes
racily accessed the template namespace because each Execute call saw
t.escapeErr == nil and re-escaped the template concurrently with read
accesses occurring outside the namespace mutex.

Add a test for this race.

Related to #12996 and CL 16104.

Fixes #16101

Change-Id: I59831d0847abbabb4ef9135f2912c6ce982f9837
Reviewed-on: https://go-review.googlesource.com/31092
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Caleb Spare 2016-10-14 00:59:19 -07:00 committed by Rob Pike
parent d8cbc2c918
commit cd2c9df761
2 changed files with 38 additions and 0 deletions
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35
src/html/template/clone_test.go
View File

@ -8,6 +8,7 @@ import (
"bytes"
"errors"
"io/ioutil"
"sync"
"testing"
"text/template/parse"
)
@ -194,3 +195,37 @@ func TestFuncMapWorksAfterClone(t *testing.T) {
t.Errorf("clone error message mismatch want %q got %q", wantErr, gotErr)
}
}
// https://golang.org/issue/16101
func TestTemplateCloneExecuteRace(t *testing.T) {
const (
input = `<title>{{block "a" .}}a{{end}}</title><body>{{block "b" .}}b{{end}}<body>`
overlay = `{{define "b"}}A{{end}}`
)
outer := Must(New("outer").Parse(input))
tmpl := Must(Must(outer.Clone()).Parse(overlay))
var wg sync.WaitGroup
for i := 0; i < 10; i++ {
wg.Add(1)
go func() {
defer wg.Done()
for i := 0; i < 100; i++ {
if err := tmpl.Execute(ioutil.Discard, "data"); err != nil {
panic(err)
}
}
}()
}
wg.Wait()
}
func TestTemplateCloneLookup(t *testing.T) {
// Template.escape makes an assumption that the template associated
// with t.Name() is t. Check that this holds.
tmpl := Must(New("x").Parse("a"))
tmpl = Must(tmpl.Clone())
if tmpl.Lookup(tmpl.Name()) != tmpl {
t.Error("after Clone, tmpl.Lookup(tmpl.Name()) != tmpl")
}
}

3
src/html/template/template.go
View File

@ -240,6 +240,9 @@ func (t *Template) Clone() (*Template, error) {
ret.set[ret.Name()] = ret
for _, x := range textClone.Templates() {
name := x.Name()
if name == ret.Name() {
continue
}
src := t.set[name]
if src == nil || src.escapeErr != nil {
return nil, fmt.Errorf("html/template: cannot Clone %q after it has executed", t.Name())