text/template: handle option missingkey=error consistently

The existing implementation of text/template handles the option
"missingkey=error" in an inconsitent manner:  If the provided data is
a nil-interface, no error is returned (despite the fact that no key
can be found in it).

This patch makes text/template return an error if "missingkey=error"
is set and the provided data is a not a valid reflect.Value.

Fixes #15356

Change-Id: Ia0a83da48652ecfaf31f18bdbd78cb21dbca1164
Reviewed-on: https://go-review.googlesource.com/31638
Reviewed-by: Rob Pike <r@golang.org>
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/text/template/exec.go b/src/text/template/exec.go
index 49f15faacde10182d31c23206452574d88376ac5..ea964dc2bcd413873e8945dabd34750a4e3ed7d5 100644 (file)
--- a/src/text/template/exec.go
+++ b/src/text/template/exec.go
@@ -541,6 +541,9 @@ func (s *state) evalFunction(dot reflect.Value, node *parse.IdentifierNode, cmd
 // value of the pipeline, if any.
 func (s *state) evalField(dot reflect.Value, fieldName string, node parse.Node, args []parse.Node, final, receiver reflect.Value) reflect.Value {
        if !receiver.IsValid() {
+               if s.tmpl.option.missingKey == mapError { // Treat invalid value as missing map key.
+                       s.errorf("nil data; no entry for key %q", fieldName)
+               }
                return zero
        }
        typ := receiver.Type()

diff --git a/src/text/template/exec_test.go b/src/text/template/exec_test.go
index 7d4af3bcbac92112c32d228fe3a7872cf275da77..5892b27391b511d8b50bf4cabe44949650ee7490 100644 (file)
--- a/src/text/template/exec_test.go
+++ b/src/text/template/exec_test.go
@@ -1142,6 +1142,12 @@ func TestMissingMapKey(t *testing.T) {
        if err == nil {
                t.Errorf("expected error; got none")
        }
+       // same Option, but now a nil interface: ask for an error
+       err = tmpl.Execute(&b, nil)
+       t.Log(err)
+       if err == nil {
+               t.Errorf("expected error for nil-interface; got none")
+       }
 }
 
 // Test that the error message for multiline unterminated string