exp/template: fixes and updates.

- fix line numbers - forgot to update state.line during execution
- add a comment convention {{/* comment */}}
- set.Template returns the named template in the set
- set.Execute executes the named template in the set
- use a local methodByName so this package can be used with earlier release of reflect.
- use initial cap to detect exported names

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/4668054

src/pkg/exp/template/exec.go

@@ -10,6 +10,8 @@ import (
 	"os"
 	"reflect"
 	"strings"
+	"unicode"
+	"utf8"
 )
 
 // state represents the state of an execution. It's not part of the
@@ -69,16 +71,20 @@ func (s *state) walk(data reflect.Value, n node) {
 			s.walk(data, node)
 		}
 	case *ifNode:
+		s.line = n.line
 		s.walkIfOrWith(nodeIf, data, n.pipeline, n.list, n.elseList)
 	case *rangeNode:
+		s.line = n.line
 		s.walkRange(data, n)
 	case *textNode:
 		if _, err := s.wr.Write(n.text); err != nil {
 			s.error(err)
 		}
 	case *templateNode:
+		s.line = n.line
 		s.walkTemplate(data, n)
 	case *withNode:
+		s.line = n.line
 		s.walkIfOrWith(nodeWith, data, n.pipeline, n.list, n.elseList)
 	default:
 		s.errorf("unknown node: %s", n)
@@ -230,6 +236,12 @@ func (s *state) evalFieldNode(data reflect.Value, field *fieldNode, args []node,
 	return s.evalFieldOrCall(data, field.ident[n-1], args, final)
 }
 
+// Is this an exported - upper case - name?
+func isExported(name string) bool {
+	rune, _ := utf8.DecodeRuneInString(name)
+	return unicode.IsUpper(rune)
+}
+
 func (s *state) evalField(data reflect.Value, fieldName string) reflect.Value {
 	for data.Kind() == reflect.Ptr {
 		data = reflect.Indirect(data)
@@ -240,7 +252,7 @@ func (s *state) evalField(data reflect.Value, fieldName string) reflect.Value {
 		field := data.FieldByName(fieldName)
 		// TODO: look higher up the tree if we can't find it here. Also unexported fields
 		// might succeed higher up, as map keys.
-		if field.IsValid() && field.Type().PkgPath() == "" { // valid and exported
+		if field.IsValid() && isExported(fieldName) { // valid and exported
 			return field
 		}
 		s.errorf("%s has no field %s", data.Type(), fieldName)
@@ -260,7 +272,7 @@ func (s *state) evalFieldOrCall(data reflect.Value, fieldName string, args []nod
 		ptr, data = data, reflect.Indirect(data)
 	}
 	// Is it a method? We use the pointer because it has value methods too.
-	if method, ok := ptr.Type().MethodByName(fieldName); ok {
+	if method, ok := methodByName(ptr.Type(), fieldName); ok {
 		return s.evalCall(ptr, method.Func, fieldName, true, args, final)
 	}
 	if len(args) > 1 || final.IsValid() {
@@ -275,6 +287,16 @@ func (s *state) evalFieldOrCall(data reflect.Value, fieldName string, args []nod
 	panic("not reached")
 }
 
+// TODO: delete when reflect's own MethodByName is released.
+func methodByName(typ reflect.Type, name string) (reflect.Method, bool) {
+	for i := 0; i < typ.NumMethod(); i++ {
+		if typ.Method(i).Name == name {
+			return typ.Method(i), true
+		}
+	}
+	return reflect.Method{}, false
+}
+
 var (
 	osErrorType = reflect.TypeOf(new(os.Error)).Elem()
 )

src/pkg/exp/template/lex.go

@@ -209,8 +209,12 @@ func lex(name, input string) *lexer {
 
 // state functions
 
-const leftMeta = "{{"
-const rightMeta = "}}"
+const (
+	leftMeta     = "{{"
+	rightMeta    = "}}"
+	leftComment  = "{{/*"
+	rightComment = "*/}}"
+)
 
 // lexText scans until a metacharacter
 func lexText(l *lexer) stateFn {
@@ -235,11 +239,25 @@ func lexText(l *lexer) stateFn {
 
 // leftMeta scans the left "metacharacter", which is known to be present.
 func lexLeftMeta(l *lexer) stateFn {
+	if strings.HasPrefix(l.input[l.pos:], leftComment) {
+		return lexComment
+	}
 	l.pos += len(leftMeta)
 	l.emit(itemLeftMeta)
 	return lexInsideAction
 }
 
+// lexComment scans a comment. The left comment marker is known to be present.
+func lexComment(l *lexer) stateFn {
+	i := strings.Index(l.input[l.pos:], rightComment)
+	if i < 0 {
+		return l.errorf("unclosed comment")
+	}
+	l.pos += i + len(rightComment)
+	l.ignore()
+	return lexText
+}
+
 // rightMeta scans the right "metacharacter", which is known to be present.
 func lexRightMeta(l *lexer) stateFn {
 	l.pos += len(rightMeta)

src/pkg/exp/template/lex_test.go

@@ -31,6 +31,11 @@ var lexTests = []lexTest{
 	{"empty", "", []item{tEOF}},
 	{"spaces", " \t\n", []item{{itemText, " \t\n"}, tEOF}},
 	{"text", `now is the time`, []item{{itemText, "now is the time"}, tEOF}},
+	{"text with comment", "hello-{{/* this is a comment */}}-world", []item{
+		{itemText, "hello-"},
+		{itemText, "-world"},
+		tEOF,
+	}},
 	{"empty action", `{{}}`, []item{tLeft, tRight, tEOF}},
 	{"for", `{{for }}`, []item{tLeft, tFor, tRight, tEOF}},
 	{"quote", `{{"abc \n\t\" "}}`, []item{tLeft, tQuote, tRight, tEOF}},

src/pkg/exp/template/parse.go

@@ -648,6 +648,7 @@ func (t *Template) pipeline(context string) (pipe []*commandNode) {
 }
 
 func (t *Template) parseControl(context string) (lineNum int, pipe []*commandNode, list, elseList *listNode) {
+	lineNum = t.lex.lineNumber()
 	pipe = t.pipeline(context)
 	var next node
 	list, next = t.itemList(false)

src/pkg/exp/template/set.go

@@ -6,6 +6,7 @@ package template
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"reflect"
 	"runtime"
@@ -49,6 +50,23 @@ func (s *Set) Add(templates ...*Template) *Set {
 	return s
 }
 
+// Template returns the template with the given name in the set,
+// or nil if there is no such template.
+func (s *Set) Template(name string) *Template {
+	return s.tmpl[name]
+}
+
+// Execute looks for the named template in the set and then applies that
+// template to the specified data object, writing the output to wr.  Nested
+// template invocations will be resolved from the set.
+func (s *Set) Execute(name string, wr io.Writer, data interface{}) os.Error {
+	tmpl := s.tmpl[name]
+	if tmpl == nil {
+		return fmt.Errorf("template: no template %q in set", name)
+	}
+	return tmpl.ExecuteInSet(wr, data, s)
+}
+
 // recover is the handler that turns panics into returns from the top
 // level of Parse.
 func (s *Set) recover(errp *os.Error) {