exp/template: simplify the helper functions

- create a pair of "Must" functions, one for templates, one for sets
- regularize the return values of the parsers so they can be wrapped by Must
- delete all the old Must functions and methods.

R=golang-dev, gri, r
CC=golang-dev
https://golang.org/cl/4826052

6 files changed, 92 insertions, 186 deletions

diff --git a/src/pkg/exp/template/exec_test.go b/src/pkg/exp/template/exec_test.go
index 05f3b90ebf..d9b8afbcd2 100644
--- a/src/pkg/exp/template/exec_test.go
+++ b/src/pkg/exp/template/exec_test.go
@@ -72,7 +72,7 @@ var tVal = &T{
 	Empty4: &U{"UinEmpty"},
 	PI:     newInt(23),
 	PSI:    newIntSlice(21, 22, 23),
-	Tmpl:   New("x").MustParse("test template"), // "x" is the value of .X
+	Tmpl:   Must(New("x").Parse("test template")), // "x" is the value of .X
 }
 
 // Helpers for creation.
@@ -359,7 +359,7 @@ func testExecute(execTests []execTest, set *Set, t *testing.T) {
 	funcs := FuncMap{"zeroArgs": zeroArgs, "oneArg": oneArg, "typeOf": typeOf}
 	for _, test := range execTests {
 		tmpl := New(test.name).Funcs(funcs)
-		err := tmpl.ParseInSet(test.input, set)
+		_, err := tmpl.ParseInSet(test.input, set)
 		if err != nil {
 			t.Errorf("%s: parse error: %s", test.name, err)
 			continue
@@ -394,7 +394,7 @@ func TestExecute(t *testing.T) {
 func TestExecuteError(t *testing.T) {
 	b := new(bytes.Buffer)
 	tmpl := New("error")
-	err := tmpl.Parse("{{.EPERM true}}")
+	_, err := tmpl.Parse("{{.EPERM true}}")
 	if err != nil {
 		t.Fatalf("parse error: %s", err)
 	}
@@ -487,7 +487,7 @@ func TestTree(t *testing.T) {
 		},
 	}
 	set := new(Set)
-	err := set.Parse(treeTemplate)
+	_, err := set.Parse(treeTemplate)
 	if err != nil {
 		t.Fatal("parse error:", err)
 	}
diff --git a/src/pkg/exp/template/helper.go b/src/pkg/exp/template/helper.go
index cf50a3082f..4187897171 100644
--- a/src/pkg/exp/template/helper.go
+++ b/src/pkg/exp/template/helper.go
@@ -15,76 +15,62 @@ import (
 
 // Functions and methods to parse a single template.
 
-// MustParse parses the template definition string to construct an internal
-// representation of the template for execution.
-// It panics if the template cannot be parsed.
-func (t *Template) MustParse(text string) *Template {
-	if err := t.Parse(text); err != nil {
+// Must is a helper that wraps a call to a function returning (*Template, os.Error)
+// and panics if the error is non-nil. It is intended for use in variable initializations
+// such as
+//	var t = template.Must(template.Parse("text"))
+func Must(t *Template, err os.Error) *Template {
+	if err != nil {
 		panic(err)
 	}
 	return t
 }
 
+// ParseFile creates a new Template and parses the template definition from
+// the named file.  The template name is the base name of the file.
+func ParseFile(filename string) (*Template, os.Error) {
+	t := New(filepath.Base(filename))
+	return t.ParseFile(filename)
+}
+
+// parseFileInSet creates a new Template and parses the template
+// definition from the named file. The template name is the base name
+// of the file. It also adds the template to the set. Function bindings are
+// checked against those in the set.
+func parseFileInSet(filename string, set *Set) (*Template, os.Error) {
+	t := New(filepath.Base(filename))
+	return t.parseFileInSet(filename, set)
+}
+
 // ParseFile reads the template definition from a file and parses it to
 // construct an internal representation of the template for execution.
-func (t *Template) ParseFile(filename string) os.Error {
+func (t *Template) ParseFile(filename string) (*Template, os.Error) {
 	b, err := ioutil.ReadFile(filename)
 	if err != nil {
-		return err
+		return t, err
 	}
 	return t.Parse(string(b))
 }
 
-// ParseFileInSet is the same as ParseFile except that function bindings
+// parseFileInSet is the same as ParseFile except that function bindings
 // are checked against those in the set and the template is added
 // to the set.
-func (t *Template) ParseFileInSet(filename string, set *Set) os.Error {
+func (t *Template) parseFileInSet(filename string, set *Set) (*Template, os.Error) {
 	b, err := ioutil.ReadFile(filename)
 	if err != nil {
-		return err
+		return t, err
 	}
 	return t.ParseInSet(string(b), set)
 }
 
-// MustParseFile reads the template definition from a file and parses it to
-// construct an internal representation of the template for execution.
-// It panics if the file cannot be read or the template cannot be parsed.
-func (t *Template) MustParseFile(filename string) *Template {
-	if err := t.ParseFile(filename); err != nil {
-		panic(err)
-	}
-	return t
-}
-
-// ParseFile creates a new Template and parses the template definition from
-// the named file.  The template name is the base name of the file.
-func ParseFile(filename string) (*Template, os.Error) {
-	t := New(filepath.Base(filename))
-	return t, t.ParseFile(filename)
-}
-
-// ParseFileInSet creates a new Template and parses the template
-// definition from the named file. The template name is the base name
-// of the file. It also adds the template to the set. Function bindings are
-//checked against those in the set.
-func ParseFileInSet(filename string, set *Set) (*Template, os.Error) {
-	t := New(filepath.Base(filename))
-	return t, t.ParseFileInSet(filename, set)
-}
-
-// MustParseFile creates a new Template and parses the template definition
-// from the named file.  The template name is the base name of the file.
-// It panics if the file cannot be read or the template cannot be parsed.
-func MustParseFile(filename string) *Template {
-	return New(filepath.Base(filename)).MustParseFile(filename)
-}
-
 // Functions and methods to parse a set.
 
-// MustParse parses a string into a set of named templates.
-// It panics if the set cannot be parsed.
-func (s *Set) MustParse(text string) *Set {
-	if err := s.Parse(text); err != nil {
+// SetMust is a helper that wraps a call to a function returning (*Set, os.Error)
+// and panics if the error is non-nil. It is intended for use in variable initializations
+// such as
+//	var s = template.SetMust(template.ParseSetFile("file"))
+func SetMust(s *Set, err os.Error) *Set {
+	if err != nil {
 		panic(err)
 	}
 	return s
@@ -93,70 +79,47 @@ func (s *Set) MustParse(text string) *Set {
 // ParseFile parses the named files into a set of named templates.
 // Each file must be parseable by itself. Parsing stops if an error is
 // encountered.
-func (s *Set) ParseFile(filenames ...string) os.Error {
+func (s *Set) ParseFile(filenames ...string) (*Set, os.Error) {
 	for _, filename := range filenames {
 		b, err := ioutil.ReadFile(filename)
 		if err != nil {
-			return err
+			return s, err
 		}
-		err = s.Parse(string(b))
+		_, err = s.Parse(string(b))
 		if err != nil {
-			return err
+			return s, err
 		}
 	}
-	return nil
-}
-
-// MustParseFile parses the named file into a set of named templates.
-// Each file must be parseable by itself.
-// MustParseFile panics if any file cannot be read or parsed.
-func (s *Set) MustParseFile(filenames ...string) *Set {
-	err := s.ParseFile(filenames...)
-	if err != nil {
-		panic(err)
-	}
-	return s
+	return s, nil
 }
 
 // ParseSetFile creates a new Set and parses the set definition from the
 // named files. Each file must be individually parseable.
-func ParseSetFile(filenames ...string) (set *Set, err os.Error) {
+func ParseSetFile(filenames ...string) (*Set, os.Error) {
 	s := new(Set)
-	var b []byte
 	for _, filename := range filenames {
-		b, err = ioutil.ReadFile(filename)
+		b, err := ioutil.ReadFile(filename)
 		if err != nil {
-			return
+			return s, err
 		}
-		err = s.Parse(string(b))
+		_, err = s.Parse(string(b))
 		if err != nil {
-			return
+			return s, err
 		}
 	}
 	return s, nil
 }
 
-// MustParseSetFile creates a new Set and parses the set definition from the
-// named files. Each file must be individually parseable.
-// MustParseSetFile panics if any file cannot be read or parsed.
-func MustParseSetFile(filenames ...string) *Set {
-	s, err := ParseSetFile(filenames...)
-	if err != nil {
-		panic(err)
-	}
-	return s
-}
-
 // ParseFiles parses the set definition from the files identified by the
 // pattern.  The pattern is processed by filepath.Glob and must match at
 // least one file.
-func (s *Set) ParseFiles(pattern string) os.Error {
+func (s *Set) ParseFiles(pattern string) (*Set, os.Error) {
 	filenames, err := filepath.Glob(pattern)
 	if err != nil {
-		return err
+		return s, err
 	}
 	if len(filenames) == 0 {
-		return fmt.Errorf("pattern matches no files: %#q", pattern)
+		return s, fmt.Errorf("pattern matches no files: %#q", pattern)
 	}
 	return s.ParseFile(filenames...)
 }
@@ -165,26 +128,13 @@ func (s *Set) ParseFiles(pattern string) os.Error {
 // files identified by the pattern. The pattern is processed by filepath.Glob
 // and must match at least one file.
 func ParseSetFiles(pattern string) (*Set, os.Error) {
-	set := new(Set)
-	err := set.ParseFiles(pattern)
+	set, err := new(Set).ParseFiles(pattern)
 	if err != nil {
-		return nil, err
+		return set, err
 	}
 	return set, nil
 }
 
-// MustParseSetFiles creates a new Set and parses the set definition from the
-// files identified by the pattern. The pattern is processed by filepath.Glob.
-// MustParseSetFiles panics if the pattern is invalid or a matched file cannot be
-// read or parsed.
-func MustParseSetFiles(pattern string) *Set {
-	set, err := ParseSetFiles(pattern)
-	if err != nil {
-		panic(err)
-	}
-	return set
-}
-
 // Functions and methods to parse stand-alone template files into a set.
 
 // ParseTemplateFile parses the named template files and adds
@@ -197,24 +147,14 @@ func MustParseSetFiles(pattern string) *Set {
 // individual templates, which are then added to the set.
 // Each file must be parseable by itself. Parsing stops if an error is
 // encountered.
-func (s *Set) ParseTemplateFile(filenames ...string) os.Error {
+func (s *Set) ParseTemplateFile(filenames ...string) (*Set, os.Error) {
 	for _, filename := range filenames {
-		_, err := ParseFileInSet(filename, s)
+		_, err := parseFileInSet(filename, s)
 		if err != nil {
-			return err
+			return s, err
 		}
 	}
-	return nil
-}
-
-// MustParseTemplateFile is like ParseTemplateFile but
-// panics if there is an error.
-func (s *Set) MustParseTemplateFile(filenames ...string) *Set {
-	err := s.ParseTemplateFile(filenames...)
-	if err != nil {
-		panic(err)
-	}
-	return s
+	return s, nil
 }
 
 // ParseTemplateFiles parses the template files matched by the
@@ -227,28 +167,18 @@ func (s *Set) MustParseTemplateFile(filenames ...string) *Set {
 // individual templates, which are then added to the set.
 // Each file must be parseable by itself. Parsing stops if an error is
 // encountered.
-func (s *Set) ParseTemplateFiles(pattern string) os.Error {
+func (s *Set) ParseTemplateFiles(pattern string) (*Set, os.Error) {
 	filenames, err := filepath.Glob(pattern)
 	if err != nil {
-		return err
+		return s, err
 	}
 	for _, filename := range filenames {
-		_, err := ParseFileInSet(filename, s)
+		_, err := parseFileInSet(filename, s)
 		if err != nil {
-			return err
+			return s, err
 		}
 	}
-	return nil
-}
-
-// MustParseTemplateFile is like ParseTemplateFiles but
-// panics if there is an error.
-func (s *Set) MustParseTemplateFiles(pattern string) *Set {
-	err := s.ParseTemplateFiles(pattern)
-	if err != nil {
-		panic(err)
-	}
-	return s
+	return s, nil
 }
 
 // ParseTemplateFile creates a set by parsing the named files,
@@ -266,25 +196,15 @@ func ParseTemplateFile(filenames ...string) (*Set, os.Error) {
 	for _, filename := range filenames {
 		t, err := ParseFile(filename)
 		if err != nil {
-			return nil, err
+			return set, err
 		}
 		if err := set.add(t); err != nil {
-			return nil, err
+			return set, err
 		}
 	}
 	return set, nil
 }
 
-// MustParseTemplateFile is like ParseTemplateFile but
-// panics if there is an error.
-func MustParseTemplateFile(filenames ...string) *Set {
-	set, err := ParseTemplateFile(filenames...)
-	if err != nil {
-		panic(err)
-	}
-	return set
-}
-
 // ParseTemplateFiles creates a set by parsing the files matched
 // by the pattern, each of which defines a single template. Each
 // template will named the base name of its file.
@@ -296,30 +216,19 @@ func MustParseTemplateFile(filenames ...string) *Set {
 // Each file must be parseable by itself. Parsing stops if an error is
 // encountered.
 func ParseTemplateFiles(pattern string) (*Set, os.Error) {
+	set := new(Set)
 	filenames, err := filepath.Glob(pattern)
 	if err != nil {
-		return nil, err
+		return set, err
 	}
-	set := new(Set)
 	for _, filename := range filenames {
 		t, err := ParseFile(filename)
 		if err != nil {
-			return nil, err
+			return set, err
 		}
 		if err := set.add(t); err != nil {
-			return nil, err
+			return set, err
 		}
 	}
 	return set, nil
 }
-
-// MustParseTemplateFiles is like ParseTemplateFiles but
-// panics if there is a parse error or other problem
-// constructing the set.
-func MustParseTemplateFiles(pattern string) *Set {
-	set, err := ParseTemplateFiles(pattern)
-	if err != nil {
-		panic(err)
-	}
-	return set
-}
diff --git a/src/pkg/exp/template/parse.go b/src/pkg/exp/template/parse.go
index aa75eb8d94..8a0b51eafd 100644
--- a/src/pkg/exp/template/parse.go
+++ b/src/pkg/exp/template/parse.go
@@ -610,25 +610,25 @@ func (t *Template) atEOF() bool {
 
 // Parse parses the template definition string to construct an internal
 // representation of the template for execution.
-func (t *Template) Parse(s string) (err os.Error) {
+func (t *Template) Parse(s string) (tmpl *Template, err os.Error) {
 	defer t.recover(&err)
 	t.startParse(t.set, lex(t.name, s))
 	t.parse(true)
 	t.stopParse()
-	return
+	return t, nil
 }
 
 // ParseInSet parses the template definition string to construct an internal
 // representation of the template for execution. It also adds the template
 // to the set.
 // Function bindings are checked against those in the set.
-func (t *Template) ParseInSet(s string, set *Set) (err os.Error) {
+func (t *Template) ParseInSet(s string, set *Set) (tmpl *Template, err os.Error) {
 	defer t.recover(&err)
 	t.startParse(set, lex(t.name, s))
 	t.parse(true)
 	t.stopParse()
 	t.addToSet(set)
-	return nil
+	return t, nil
 }
 
 // addToSet adds the template to the set, verifying it's not being double-assigned.
diff --git a/src/pkg/exp/template/parse_test.go b/src/pkg/exp/template/parse_test.go
index 6b4ca1989f..fb8956a465 100644
--- a/src/pkg/exp/template/parse_test.go
+++ b/src/pkg/exp/template/parse_test.go
@@ -230,8 +230,7 @@ var parseTests = []parseTest{
 
 func TestParse(t *testing.T) {
 	for _, test := range parseTests {
-		tmpl := New(test.name)
-		err := tmpl.Parse(test.input)
+		tmpl, err := New(test.name).Parse(test.input)
 		switch {
 		case err == nil && !test.ok:
 			t.Errorf("%q: expected error; got none", test.name)
diff --git a/src/pkg/exp/template/set.go b/src/pkg/exp/template/set.go
index dc64b4c9c3..a685e996de 100644
--- a/src/pkg/exp/template/set.go
+++ b/src/pkg/exp/template/set.go
@@ -99,7 +99,8 @@ func (s *Set) recover(errp *os.Error) {
 // multiple times for a given set, adding the templates defined in the string
 // to the set.  If a template is redefined, the element in the set is
 // overwritten with the new definition.
-func (s *Set) Parse(text string) (err os.Error) {
+func (s *Set) Parse(text string) (set *Set, err os.Error) {
+	set = s
 	s.init()
 	defer s.recover(&err)
 	lex := lex("set", text)
@@ -130,5 +131,5 @@ func (s *Set) Parse(text string) (err os.Error) {
 		t.addToSet(s)
 		s.tmpl[t.name] = t
 	}
-	return nil
+	return s, nil
 }
diff --git a/src/pkg/exp/template/set_test.go b/src/pkg/exp/template/set_test.go
index c42d97a07b..4f2d76e207 100644
--- a/src/pkg/exp/template/set_test.go
+++ b/src/pkg/exp/template/set_test.go
@@ -38,8 +38,7 @@ var setParseTests = []setParseTest{
 
 func TestSetParse(t *testing.T) {
 	for _, test := range setParseTests {
-		set := new(Set)
-		err := set.Parse(test.input)
+		set, err := new(Set).Parse(test.input)
 		switch {
 		case err == nil && !test.ok:
 			t.Errorf("%q: expected error; got none", test.name)
@@ -54,6 +53,9 @@ func TestSetParse(t *testing.T) {
 			}
 			continue
 		}
+		if set == nil {
+			continue
+		}
 		if len(set.tmpl) != len(test.names) {
 			t.Errorf("%s: wrong number of templates; wanted %d got %d", test.name, len(test.names), len(set.tmpl))
 			continue
@@ -101,12 +103,11 @@ const setText2 = `
 
 func TestSetExecute(t *testing.T) {
 	// Declare a set with a couple of templates first.
-	set := new(Set)
-	err := set.Parse(setText1)
+	set, err := new(Set).Parse(setText1)
 	if err != nil {
 		t.Fatalf("error parsing set: %s", err)
 	}
-	err = set.Parse(setText2)
+	_, err = set.Parse(setText2)
 	if err != nil {
 		t.Fatalf("error parsing set: %s", err)
 	}
@@ -114,12 +115,11 @@ func TestSetExecute(t *testing.T) {
 }
 
 func TestSetParseFile(t *testing.T) {
-	set := new(Set)
-	err := set.ParseFile("DOES NOT EXIST")
+	set, err := new(Set).ParseFile("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
-	err = set.ParseFile("testdata/file1.tmpl", "testdata/file2.tmpl")
+	_, err = set.ParseFile("testdata/file1.tmpl", "testdata/file2.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}
@@ -139,16 +139,15 @@ func TestParseSetFile(t *testing.T) {
 }
 
 func TestSetParseFiles(t *testing.T) {
-	set := new(Set)
-	err := set.ParseFiles("DOES NOT EXIST")
+	set, err := new(Set).ParseFiles("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
-	err = set.ParseFiles("[x")
+	_, err = set.ParseFiles("[x")
 	if err == nil {
 		t.Error("expected error for bad pattern; got none")
 	}
-	err = set.ParseFiles("testdata/file*.tmpl")
+	_, err = set.ParseFiles("testdata/file*.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}
@@ -172,16 +171,15 @@ func TestParseSetFiles(t *testing.T) {
 }
 
 var templateFileExecTests = []execTest{
-	{"teset", `{{template "tmpl1.tmpl"}}{{template "tmpl2.tmpl"}}`, "template1\ntemplate2\n", 0, true},
+	{"test", `{{template "tmpl1.tmpl"}}{{template "tmpl2.tmpl"}}`, "template1\ntemplate2\n", 0, true},
 }
 
 func TestSetParseTemplateFile(t *testing.T) {
-	set := new(Set)
-	err := set.ParseTemplateFile("DOES NOT EXIST")
+	set, err := ParseTemplateFile("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
-	err = set.ParseTemplateFile("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
+	_, err = set.ParseTemplateFile("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}
@@ -201,16 +199,15 @@ func TestParseTemplateFile(t *testing.T) {
 }
 
 func TestSetParseTemplateFiles(t *testing.T) {
-	set := new(Set)
-	err := set.ParseTemplateFiles("DOES NOT EXIST")
+	set, err := ParseTemplateFiles("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
-	err = set.ParseTemplateFiles("[x")
+	_, err = set.ParseTemplateFiles("[x")
 	if err == nil {
 		t.Error("expected error for bad pattern; got none")
 	}
-	err = set.ParseTemplateFiles("testdata/tmpl*.tmpl")
+	_, err = set.ParseTemplateFiles("testdata/tmpl*.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}