exp/template: add templates to sets; boolean logic.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/4670045

src/pkg/exp/template/exec.go

@@ -89,7 +89,23 @@ func (s *state) walk(data reflect.Value, n node) {
 // are identical in behavior except that 'with' sets dot.
 func (s *state) walkIfOrWith(typ nodeType, data reflect.Value, pipe []*commandNode, list, elseList *listNode) {
 	val := s.evalPipeline(data, pipe)
-	truth := false
+	truth, ok := isTrue(val)
+	if !ok {
+		s.errorf("if/with can't use value of type %T", val.Interface())
+	}
+	if truth {
+		if typ == nodeWith {
+			data = val
+		}
+		s.walk(data, list)
+	} else if elseList != nil {
+		s.walk(data, elseList)
+	}
+}
+
+// isTrue returns whether the value is 'true', in the sense of not the zero of its type,
+// and whether the value has a meaningful truth value.
+func isTrue(val reflect.Value) (truth, ok bool) {
 	switch val.Kind() {
 	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
 		truth = val.Len() > 0
@@ -106,16 +122,9 @@ func (s *state) walkIfOrWith(typ nodeType, data reflect.Value, pipe []*commandNo
 	case reflect.Chan, reflect.Func, reflect.Ptr:
 		truth = !val.IsNil()
 	default:
-		s.errorf("if/with can't use value of type %T", val.Interface())
+		return
-	}
-	if truth {
-		if typ == nodeWith {
-			data = val
-		}
-		s.walk(data, list)
-	} else if elseList != nil {
-		s.walk(data, elseList)
 	}
+	return truth, true
 }
 
 func (s *state) walkRange(data reflect.Value, r *rangeNode) {

src/pkg/exp/template/exec_test.go

@@ -140,7 +140,7 @@ var execTests = []execTest{
 	{"if slice", "{{if .SI}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
 	{"if emptymap", "{{if .MSIEmpty}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
 	{"if map", "{{if .MSI}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
-	// Function calls.
+	// Printf.
 	{"printf", `{{printf "hello, printf"}}`, "hello, printf", tVal, true},
 	{"printf int", `{{printf "%04x" 127}}`, "007f", tVal, true},
 	{"printf float", `{{printf "%g" 3.5}}`, "3.5", tVal, true},
@@ -150,10 +150,17 @@ var execTests = []execTest{
 	{"printf field", `{{printf "%s" .U.V}}`, "v", tVal, true},
 	{"printf method", `{{printf "%s" .Method0}}`, "resultOfMethod0", tVal, true},
 	{"printf lots", `{{printf "%d %s %g %s" 127 "hello" 7-3i .Method0}}`, "127 hello (7-3i) resultOfMethod0", tVal, true},
+	// HTML.
 	{"html", `{{html "<script>alert(\"XSS\");</script>"}}`,
-		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", tVal, true},
+		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", nil, true},
 	{"html pipeline", `{{printf "<script>alert(\"XSS\");</script>" | html}}`,
-		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", tVal, true},
+		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", nil, true},
+	// Booleans
+	{"not", "{{not true}} {{not false}}", "false true", nil, true},
+	{"and", "{{and 0 0}} {{and 1 0}} {{and 0 1}} {{and 1 1}}", "false false false true", nil, true},
+	{"or", "{{or 0 0}} {{or 1 0}} {{or 0 1}} {{or 1 1}}", "false true true true", 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},
 	// With.
 	{"with true", "{{with true}}{{.}}{{end}}", "true", tVal, true},
 	{"with false", "{{with false}}{{.}}{{else}}FALSE{{end}}", "FALSE", tVal, true},

src/pkg/exp/template/funcs.go

@@ -20,6 +20,9 @@ type FuncMap map[string]interface{}
 var funcs = map[string]reflect.Value{
 	"printf": reflect.ValueOf(fmt.Sprintf),
 	"html":   reflect.ValueOf(HTMLEscaper),
+	"and":    reflect.ValueOf(and),
+	"or":     reflect.ValueOf(or),
+	"not":    reflect.ValueOf(not),
 }
 
 // addFuncs adds to values the functions in funcs, converting them to reflect.Values.
@@ -66,7 +69,33 @@ func findFunction(name string, tmpl *Template, set *Set) (reflect.Value, bool) {
 	return reflect.Value{}, false
 }
 
-// HTML escaping
+// Boolean logic.
+
+// and returns the Boolean AND of its arguments.
+func and(arg0 interface{}, args ...interface{}) (truth bool) {
+	truth, _ = isTrue(reflect.ValueOf(arg0))
+	for i := 0; truth && i < len(args); i++ {
+		truth, _ = isTrue(reflect.ValueOf(args[i]))
+	}
+	return
+}
+
+// or returns the Boolean OR of its arguments.
+func or(arg0 interface{}, args ...interface{}) (truth bool) {
+	truth, _ = isTrue(reflect.ValueOf(arg0))
+	for i := 0; !truth && i < len(args); i++ {
+		truth, _ = isTrue(reflect.ValueOf(args[i]))
+	}
+	return
+}
+
+// not returns the Boolean negation of its argument.
+func not(arg interface{}) (truth bool) {
+	truth, _ = isTrue(reflect.ValueOf(arg))
+	return !truth
+}
+
+// HTML escaping.
 
 var (
 	escQuot = []byte("&#34;") // shorter than "&quot;"

src/pkg/exp/template/set.go

@@ -5,6 +5,7 @@
 package template
 
 import (
+	"fmt"
 	"os"
 	"reflect"
 	"runtime"
@@ -35,6 +36,19 @@ func (s *Set) Funcs(funcMap FuncMap) *Set {
 	return s
 }
 
+// Add adds the argument templates to the set. It panics if the call
+// attempts to reuse a name defined in the template.
+// The return value is the set, so calls can be chained.
+func (s *Set) Add(templates ...*Template) *Set {
+	for _, t := range templates {
+		if _, ok := s.tmpl[t.name]; ok {
+			panic(fmt.Errorf("template: %q already defined in set", t.name))
+		}
+		s.tmpl[t.name] = t
+	}
+	return s
+}
+
 // recover is the handler that turns panics into returns from the top
 // level of Parse.
 func (s *Set) recover(errp *os.Error) {