template: add ParseFile, MustParseFile, and associated tests

R=r
CC=golang-dev
https://golang.org/cl/391041

src/pkg/template/template.go

@@ -66,6 +66,7 @@ import (
 	"container/vector"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"reflect"
 	"runtime"
@@ -965,6 +966,19 @@ func Parse(s string, fmap FormatterMap) (t *Template, err os.Error) {
 	return
 }
 
+// ParseFile is a wrapper function that creates a Template with default
+// parameters (such as {} for // metacharacters).  The filename identfies
+// a file containing the template text, while the formatter map fmap, which
+// may be nil, defines auxiliary functions for formatting variables.
+// The template is returned. If any errors occur, err will be non-nil.
+func ParseFile(filename string, fmap FormatterMap) (t *Template, err os.Error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	return Parse(string(b), fmap)
+}
+
 // MustParse is like Parse but panics if the template cannot be parsed.
 func MustParse(s string, fmap FormatterMap) *Template {
 	t, err := Parse(s, fmap)
@@ -973,3 +987,13 @@ func MustParse(s string, fmap FormatterMap) *Template {
 	}
 	return t
 }
+
+// MustParseFile is like ParseFile but panics if the file cannot be read
+// or the template cannot be parsed.
+func MustParseFile(filename string, fmap FormatterMap) *Template {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		panic("template parse error: ", err.String())
+	}
+	return MustParse(string(b), fmap)
+}

src/pkg/template/template_test.go

@@ -9,7 +9,9 @@ import (
 	"container/vector"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"json"
+	"os"
 	"testing"
 )
 
@@ -386,6 +388,16 @@ var tests = []*Test{
 }
 
 func TestAll(t *testing.T) {
+	// Parse
+	testAll(t, func(test *Test) (*Template, os.Error) { return Parse(test.in, formatters) })
+	// ParseFile
+	testAll(t, func(test *Test) (*Template, os.Error) {
+		ioutil.WriteFile("_test/test.tmpl", []byte(test.in), 0600)
+		return ParseFile("_test/test.tmpl", formatters)
+	})
+}
+
+func testAll(t *testing.T, parseFunc func(*Test) (*Template, os.Error)) {
 	s := new(S)
 	// initialized by hand for clarity.
 	s.header = "Header"
@@ -415,7 +427,7 @@ func TestAll(t *testing.T) {
 	var buf bytes.Buffer
 	for _, test := range tests {
 		buf.Reset()
-		tmpl, err := Parse(test.in, formatters)
+		tmpl, err := parseFunc(test)
 		if err != nil {
 			t.Error("unexpected parse error:", err)
 			continue