text/template: never call reflect.Zero(nil)
It makes no sense to try to get the zero value of a nil type, hence the
panic. When we have a nil type, use reflect.ValueOf(nil) instead.
This was showing itself if one used a missing field on the data between
parentheses, when the data was a nil interface:
t := template.Must(template.New("test").Parse(`{{ (.).foo }}`))
var v interface{}
t.Execute(os.Stdout, v)
Resulting in:
panic: reflect: Zero(nil) [recovered]
panic: reflect: Zero(nil)
Fixes #21171.
Change-Id: Ifcc4a0c67e6df425b65bc9f82fde6fcf03828579
Reviewed-on: https://go-review.googlesource.com/84482
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/src/text/template/exec.go b/src/text/template/exec.go
index 83c38cd..2ed5272 100644
--- a/src/text/template/exec.go
+++ b/src/text/template/exec.go
@@ -691,8 +691,12 @@
// validateType guarantees that the value is valid and assignable to the type.
func (s *state) validateType(value reflect.Value, typ reflect.Type) reflect.Value {
if !value.IsValid() {
- if typ == nil || canBeNil(typ) {
+ if typ == nil {
// An untyped nil interface{}. Accept as a proper nil value.
+ return reflect.ValueOf(nil)
+ }
+ if canBeNil(typ) {
+ // Like above, but use the zero value of the non-nil type.
return reflect.Zero(typ)
}
s.errorf("invalid value; expected %s", typ)
diff --git a/src/text/template/exec_test.go b/src/text/template/exec_test.go
index d0cda6b..e33e079 100644
--- a/src/text/template/exec_test.go
+++ b/src/text/template/exec_test.go
@@ -330,6 +330,10 @@
{"empty with struct", "{{.Empty4}}", "{UinEmpty}", tVal, true},
{"empty with struct, field", "{{.Empty4.V}}", "UinEmpty", tVal, true},
+ // Edge cases with <no value> with an interface value
+ {"field on interface", "{{.foo}}", "<no value>", nil, true},
+ {"field on parenthesized interface", "{{(.).foo}}", "<no value>", nil, true},
+
// Method calls.
{".Method0", "-{{.Method0}}-", "-M0-", tVal, true},
{".Method1(1234)", "-{{.Method1 1234}}-", "-1234-", tVal, true},
