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exp/template: dig into empty interfaces so a struct (say) stored in an empty

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interface field can be unpacked. We don't have type assertions here so we
must be forthright.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/4757047
This commit is contained in:
Rob Pike 2011-07-18 17:34:42 +10:00
parent ab55133ca9
commit 9a5bb287e8
2 changed files with 10 additions and 5 deletions
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8
src/pkg/exp/template/exec.go
View File

@ -589,12 +589,16 @@ func (s *state) evalEmptyInterface(dot reflect.Value, n node) reflect.Value {
} }
// indirect returns the item at the end of indirection, and a bool to indicate if it's nil. // indirect returns the item at the end of indirection, and a bool to indicate if it's nil.
// We indirect through pointers and empty interfaces (only) because
// non-empty interfaces have methods we might need.
func indirect(v reflect.Value) (rv reflect.Value, isNil bool) { func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
for v.Kind() == reflect.Ptr { for v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface {
if v.IsNil() { if v.IsNil() {
return v, true return v, true
} }
v = v.Elem() if v.Kind() == reflect.Ptr || v.NumMethod() == 0 {
v = v.Elem()
}
} }
return v, false return v, false
} }

7
src/pkg/exp/template/exec_test.go
View File

@ -69,7 +69,7 @@ var tVal = &T{
Empty1: 3, Empty1: 3,
Empty2: "empty2", Empty2: "empty2",
Empty3: []int{7, 8}, Empty3: []int{7, 8},
Empty4: &U{"v"}, Empty4: &U{"UinEmpty"},
PI: newInt(23), PI: newInt(23),
PSI: newIntSlice(21, 22, 23), PSI: newIntSlice(21, 22, 23),
Tmpl: New("x").MustParse("test template"), // "x" is the value of .X Tmpl: New("x").MustParse("test template"), // "x" is the value of .X
@ -210,7 +210,8 @@ var execTests = []execTest{
{"empty with int", "{{.Empty1}}", "3", tVal, true}, {"empty with int", "{{.Empty1}}", "3", tVal, true},
{"empty with string", "{{.Empty2}}", "empty2", tVal, true}, {"empty with string", "{{.Empty2}}", "empty2", tVal, true},
{"empty with slice", "{{.Empty3}}", "[7 8]", tVal, true}, {"empty with slice", "{{.Empty3}}", "[7 8]", tVal, true},
{"empty with struct", "{{.Empty4}}", "{v}", tVal, true}, {"empty with struct", "{{.Empty4}}", "{UinEmpty}", tVal, true},
{"empty with struct, field", "{{.Empty4.V}}", "UinEmpty", tVal, true},
// Method calls. // Method calls.
{".Method0", "-{{.Method0}}-", "-M0-", tVal, true}, {".Method0", "-{{.Method0}}-", "-M0-", tVal, true},
@ -308,7 +309,7 @@ var execTests = []execTest{
{"with slice", "{{with .SI}}{{.}}{{else}}EMPTY{{end}}", "[3 4 5]", tVal, true}, {"with slice", "{{with .SI}}{{.}}{{else}}EMPTY{{end}}", "[3 4 5]", tVal, true},
{"with emptymap", "{{with .MSIEmpty}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true}, {"with emptymap", "{{with .MSIEmpty}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
{"with map", "{{with .MSIone}}{{.}}{{else}}EMPTY{{end}}", "map[one:1]", tVal, true}, {"with map", "{{with .MSIone}}{{.}}{{else}}EMPTY{{end}}", "map[one:1]", tVal, true},
{"with empty interface, struct field", "{{with .Empty4}}{{.V}}{{end}}", "v", tVal, true}, {"with empty interface, struct field", "{{with .Empty4}}{{.V}}{{end}}", "UinEmpty", tVal, true},
{"with $x int", "{{with $x := .I}}{{$x}}{{end}}", "17", tVal, true}, {"with $x int", "{{with $x := .I}}{{$x}}{{end}}", "17", tVal, true},
{"with $x struct.U.V", "{{with $x := $}}{{$x.U.V}}{{end}}", "v", tVal, true}, {"with $x struct.U.V", "{{with $x := $}}{{$x.U.V}}{{end}}", "v", tVal, true},
{"with variable and action", "{{with $x := $}}{{$y := $.U.V}},{{$y}}{{end}}", "v,v", tVal, true}, {"with variable and action", "{{with $x := $}}{{$y := $.U.V}},{{$y}}{{end}}", "v,v", tVal, true},