text/template: only unwrap final and/or value

In the last CL I missed the fact that except for the final value the
code already unwraps the argument.

For #31103

Change-Id: Ic9099aeb50c6b3322fc14a90ac8026c1d8cb1698
Reviewed-on: https://go-review.googlesource.com/c/go/+/354091
Trust: Ian Lance Taylor <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Reviewed-by: Bryan C. Mills <[email protected]>

src/text/template/exec.go

@@ -728,13 +728,21 @@ func (s *state) evalCall(dot, fun reflect.Value, isBuiltin bool, node parse.Node
  for _, arg := range args {
  v = s.evalArg(dot, argType, arg).Interface().(reflect.Value)
  if truth(v) == (name == "or") {
- return unwrap(v)
+ // This value was already unwrapped
+ // by the .Interface().(reflect.Value).
+ return v
  }
  }
  if final != missingVal {
- v = s.validateType(final, argType)
+ // The last argument to and/or is coming from
+ // the pipeline. We didn't short circuit on an earlier
+ // argument, so we are going to return this one.
+ // We don't have to evaluate final, but we do
+ // have to check its type. Then, since we are
+ // going to return it, we have to unwrap it.
+ v = unwrap(s.validateType(final, argType))
  }
- return unwrap(v)
+ return v
  }
 
  // Build the arg list.

src/text/template/exec_test.go

@@ -489,6 +489,8 @@ var execTests = []execTest{
  {"and pipe-false", "{{0 | and 1}}", "0", nil, true},
  {"or pipe-true", "{{1 | or 0}}", "1", nil, true},
  {"or pipe-false", "{{0 | or 0}}", "0", nil, true},
+ {"and undef", "{{and 1 .Unknown}}", "<no value>", nil, true},
+ {"or undef", "{{or 0 .Unknown}}", "<no value>", nil, true},
  {"boolean if", "{{if and true 1 `hi`}}TRUE{{else}}FALSE{{end}}", "TRUE", tVal, true},
  {"boolean if not", "{{if and true 1 `hi` | not}}TRUE{{else}}FALSE{{end}}", "FALSE", nil, true},
  {"boolean if pipe", "{{if true | not | and 1}}TRUE{{else}}FALSE{{end}}", "FALSE", nil, true},