exp/template: return nil value from helpers on error, even methods.

R=rsc
CC=golang-dev
https://golang.org/cl/4835046

src/pkg/exp/template/helper.go

@@ -44,10 +44,11 @@ func parseFileInSet(filename string, set *Set) (*Template, os.Error) {
 
 // ParseFile reads the template definition from a file and parses it to
 // construct an internal representation of the template for execution.
+// The returned template will be nil if an error occurs.
 func (t *Template) ParseFile(filename string) (*Template, os.Error) {
 	b, err := ioutil.ReadFile(filename)
 	if err != nil {
-		return t, err
+		return nil, err
 	}
 	return t.Parse(string(b))
 }
@@ -55,10 +56,11 @@ func (t *Template) ParseFile(filename string) (*Template, os.Error) {
 // 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.
+// The returned template will be nil if an error occurs.
 func (t *Template) parseFileInSet(filename string, set *Set) (*Template, os.Error) {
 	b, err := ioutil.ReadFile(filename)
 	if err != nil {
-		return t, err
+		return nil, err
 	}
 	return t.ParseInSet(string(b), set)
 }
@@ -77,17 +79,17 @@ func SetMust(s *Set, err os.Error) *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.
+// Each file must be parseable by itself.
+// If an error occurs, parsing stops and the returned set is nil.
 func (s *Set) ParseFile(filenames ...string) (*Set, os.Error) {
 	for _, filename := range filenames {
 		b, err := ioutil.ReadFile(filename)
 		if err != nil {
-			return s, err
+			return nil, err
 		}
 		_, err = s.Parse(string(b))
 		if err != nil {
-			return s, err
+			return nil, err
 		}
 	}
 	return s, nil
@@ -97,15 +99,14 @@ func (s *Set) ParseFile(filenames ...string) (*Set, os.Error) {
 // named files. Each file must be individually parseable.
 func ParseSetFile(filenames ...string) (*Set, os.Error) {
 	s := new(Set)
-	s.init()
 	for _, filename := range filenames {
 		b, err := ioutil.ReadFile(filename)
 		if err != nil {
-			return s, err
+			return nil, err
 		}
 		_, err = s.Parse(string(b))
 		if err != nil {
-			return s, err
+			return nil, err
 		}
 	}
 	return s, nil
@@ -114,13 +115,14 @@ func ParseSetFile(filenames ...string) (*Set, os.Error) {
 // 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.
+// If an error occurs, parsing stops and the returned set is nil.
 func (s *Set) ParseFiles(pattern string) (*Set, os.Error) {
 	filenames, err := filepath.Glob(pattern)
 	if err != nil {
-		return s, err
+		return nil, err
 	}
 	if len(filenames) == 0 {
-		return s, fmt.Errorf("pattern matches no files: %#q", pattern)
+		return nil, fmt.Errorf("pattern matches no files: %#q", pattern)
 	}
 	return s.ParseFile(filenames...)
 }
@@ -131,7 +133,7 @@ func (s *Set) ParseFiles(pattern string) (*Set, os.Error) {
 func ParseSetFiles(pattern string) (*Set, os.Error) {
 	set, err := new(Set).ParseFiles(pattern)
 	if err != nil {
-		return set, err
+		return nil, err
 	}
 	return set, nil
 }
@@ -146,13 +148,13 @@ func ParseSetFiles(pattern string) (*Set, os.Error) {
 // file does not contain {{define}} clauses. ParseTemplateFile is
 // therefore equivalent to calling the ParseFile function to create
 // individual templates, which are then added to the set.
-// Each file must be parseable by itself. Parsing stops if an error is
-// encountered.
+// Each file must be parseable by itself.
+// If an error occurs, parsing stops and the returned set is nil.
 func (s *Set) ParseTemplateFile(filenames ...string) (*Set, os.Error) {
 	for _, filename := range filenames {
 		_, err := parseFileInSet(filename, s)
 		if err != nil {
-			return s, err
+			return nil, err
 		}
 	}
 	return s, nil
@@ -166,17 +168,17 @@ func (s *Set) ParseTemplateFile(filenames ...string) (*Set, os.Error) {
 // file does not contain {{define}} clauses. ParseTemplateFiles is
 // therefore equivalent to calling the ParseFile function to create
 // individual templates, which are then added to the set.
-// Each file must be parseable by itself. Parsing stops if an error is
-// encountered.
+// Each file must be parseable by itself.
+// If an error occurs, parsing stops and the returned set is nil.
 func (s *Set) ParseTemplateFiles(pattern string) (*Set, os.Error) {
 	filenames, err := filepath.Glob(pattern)
 	if err != nil {
-		return s, err
+		return nil, err
 	}
 	for _, filename := range filenames {
 		_, err := parseFileInSet(filename, s)
 		if err != nil {
-			return s, err
+			return nil, err
 		}
 	}
 	return s, nil
@@ -198,10 +200,10 @@ func ParseTemplateFile(filenames ...string) (*Set, os.Error) {
 	for _, filename := range filenames {
 		t, err := ParseFile(filename)
 		if err != nil {
-			return set, err
+			return nil, err
 		}
 		if err := set.add(t); err != nil {
-			return set, err
+			return nil, err
 		}
 	}
 	return set, nil
@@ -219,18 +221,17 @@ func ParseTemplateFile(filenames ...string) (*Set, os.Error) {
 // encountered.
 func ParseTemplateFiles(pattern string) (*Set, os.Error) {
 	set := new(Set)
-	set.init()
 	filenames, err := filepath.Glob(pattern)
 	if err != nil {
-		return set, err
+		return nil, err
 	}
 	for _, filename := range filenames {
 		t, err := ParseFile(filename)
 		if err != nil {
-			return set, err
+			return nil, err
 		}
 		if err := set.add(t); err != nil {
-			return set, err
+			return nil, err
 		}
 	}
 	return set, nil

src/pkg/exp/template/set.go

@@ -110,7 +110,7 @@ func (s *Set) Parse(text string) (set *Set, err os.Error) {
 		t.startParse(s, lex)
 		// Expect EOF or "{{ define name }}".
 		if t.atEOF() {
-			return
+			return nil, err
 		}
 		t.expect(itemLeftDelim, context)
 		t.expect(itemDefine, context)

src/pkg/exp/template/set_test.go

@@ -103,7 +103,8 @@ const setText2 = `
 
 func TestSetExecute(t *testing.T) {
 	// Declare a set with a couple of templates first.
-	set, err := new(Set).Parse(setText1)
+	set := new(Set)
+	_, err := set.Parse(setText1)
 	if err != nil {
 		t.Fatalf("error parsing set: %s", err)
 	}
@@ -115,7 +116,8 @@ func TestSetExecute(t *testing.T) {
 }
 
 func TestSetParseFile(t *testing.T) {
-	set, err := new(Set).ParseFile("DOES NOT EXIST")
+	set := new(Set)
+	_, err := set.ParseFile("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
@@ -127,7 +129,8 @@ func TestSetParseFile(t *testing.T) {
 }
 
 func TestParseSetFile(t *testing.T) {
-	set, err := ParseSetFile("DOES NOT EXIST")
+	set := new(Set)
+	_, err := ParseSetFile("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
@@ -139,15 +142,15 @@ func TestParseSetFile(t *testing.T) {
 }
 
 func TestSetParseFiles(t *testing.T) {
-	set, err := new(Set).ParseFiles("DOES NOT EXIST")
+	_, 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 = new(Set).ParseFiles("[x")
 	if err == nil {
 		t.Error("expected error for bad pattern; got none")
 	}
-	_, err = set.ParseFiles("testdata/file*.tmpl")
+	set, err := new(Set).ParseFiles("testdata/file*.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}
@@ -155,15 +158,15 @@ func TestSetParseFiles(t *testing.T) {
 }
 
 func TestParseSetFiles(t *testing.T) {
-	set, err := ParseSetFiles("DOES NOT EXIST")
+	_, err := ParseSetFiles("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
-	set, err = ParseSetFiles("[x")
+	_, err = ParseSetFiles("[x")
 	if err == nil {
 		t.Error("expected error for bad pattern; got none")
 	}
-	set, err = ParseSetFiles("testdata/file*.tmpl")
+	set, err := ParseSetFiles("testdata/file*.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}
@@ -175,11 +178,11 @@ var templateFileExecTests = []execTest{
 }
 
 func TestSetParseTemplateFile(t *testing.T) {
-	set, err := ParseTemplateFile("DOES NOT EXIST")
+	_, 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")
+	set, err := new(Set).ParseTemplateFile("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}
@@ -187,11 +190,11 @@ func TestSetParseTemplateFile(t *testing.T) {
 }
 
 func TestParseTemplateFile(t *testing.T) {
-	set, err := ParseTemplateFile("DOES NOT EXIST")
+	_, err := ParseTemplateFile("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
-	set, err = ParseTemplateFile("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
+	set, err := new(Set).ParseTemplateFile("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}
@@ -199,15 +202,15 @@ func TestParseTemplateFile(t *testing.T) {
 }
 
 func TestSetParseTemplateFiles(t *testing.T) {
-	set, err := ParseTemplateFiles("DOES NOT EXIST")
+	_, err := ParseTemplateFiles("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
-	_, err = set.ParseTemplateFiles("[x")
+	_, err = new(Set).ParseTemplateFiles("[x")
 	if err == nil {
 		t.Error("expected error for bad pattern; got none")
 	}
-	_, err = set.ParseTemplateFiles("testdata/tmpl*.tmpl")
+	set, err := new(Set).ParseTemplateFiles("testdata/tmpl*.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}
@@ -215,15 +218,15 @@ func TestSetParseTemplateFiles(t *testing.T) {
 }
 
 func TestParseTemplateFiles(t *testing.T) {
-	set, err := ParseTemplateFiles("DOES NOT EXIST")
+	_, err := ParseTemplateFiles("DOES NOT EXIST")
 	if err == nil {
 		t.Error("expected error for non-existent file; got none")
 	}
-	set, err = ParseTemplateFiles("[x")
+	_, err = ParseTemplateFiles("[x")
 	if err == nil {
 		t.Error("expected error for bad pattern; got none")
 	}
-	set, err = ParseTemplateFiles("testdata/tmpl*.tmpl")
+	set, err := ParseTemplateFiles("testdata/tmpl*.tmpl")
 	if err != nil {
 		t.Fatalf("error parsing files: %v", err)
 	}