text/template: replace Add with AddParseTree

Makes it clear we're adding exactly one tree and creating a
new template for it.

R=rsc
CC=golang-dev
https://golang.org/cl/5448077

2 files changed, 37 insertions, 14 deletions

diff --git a/src/pkg/text/template/multi_test.go b/src/pkg/text/template/multi_test.go
index bf4f3078b3..7b35d2633d 100644
--- a/src/pkg/text/template/multi_test.go
+++ b/src/pkg/text/template/multi_test.go
@@ -10,6 +10,7 @@ import (
 	"bytes"
 	"fmt"
 	"testing"
+	"text/template/parse"
 )
 
 type isEmptyTest struct {
@@ -258,3 +259,30 @@ func TestClone(t *testing.T) {
 		t.Errorf("expected %q got %q", "bclone", b.String())
 	}
 }
+
+func TestAddParseTree(t *testing.T) {
+	// Create some templates.
+	root, err := New("root").Parse(cloneText1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = root.Parse(cloneText2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Add a new parse tree.
+	tree, err := parse.Parse("cloneText3", cloneText3, "", "", nil, builtins)
+	if err != nil {
+		t.Fatal(err)
+	}
+	added, err := root.AddParseTree("c", tree["c"])
+	// Execute.
+	var b bytes.Buffer
+	err = added.ExecuteTemplate(&b, "a", 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if b.String() != "broot" {
+		t.Errorf("expected %q got %q", "broot", b.String())
+	}
+}
diff --git a/src/pkg/text/template/template.go b/src/pkg/text/template/template.go
index c1d0c1c349..04fca407c1 100644
--- a/src/pkg/text/template/template.go
+++ b/src/pkg/text/template/template.go
@@ -103,21 +103,16 @@ func (t *Template) copy(c *common) *Template {
 	return nt
 }
 
-// Add associates the argument template, arg, with t, and vice versa,
-// so they may invoke each other. To do this, it also removes any
-// prior associations arg may have. Except for losing the link to
-// arg, templates associated with arg are otherwise unaffected. It
-// is an error if the argument template's name is already associated
-// with t.  Add is here to support html/template and is not intended
-// for other uses.
-// TODO: make this take a parse.Tree argument instead of a template.
-func (t *Template) Add(arg *Template) error {
-	if t.tmpl[arg.name] != nil {
-		return fmt.Errorf("template: redefinition of template %q", arg.name)
+// AddParseTree creates a new template with the name and parse tree
+// and associates it with t.
+func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
+	if t.tmpl[name] != nil {
+		return nil, fmt.Errorf("template: redefinition of template %q", name)
 	}
-	arg.common = t.common
-	t.tmpl[arg.name] = arg
-	return nil
+	nt := t.New(name)
+	nt.Tree = tree
+	t.tmpl[name] = nt
+	return nt, nil
 }
 
 // Templates returns a slice of the templates associated with t, including t