tpl/internal: Synch Go templates fork with Go 1.16dev

scripts/fork_go_templates/main.go

@@ -18,7 +18,7 @@ import (
 
 func main() {
 	// TODO(bep) git checkout tag
-	// The current is built with Go version b68fa57c599720d33a2d735782969ce95eabf794 / go1.15dev
+	// The current is built with Go version da54dfb6a1f3bef827b9ec3780c98fde77a97d11 / go1.16dev
 	fmt.Println("Forking ...")
 	defer fmt.Println("Done ...")
 

tpl/internal/go_templates/cfg/cfg.go

@@ -58,6 +58,7 @@ const KnownEnv = `
 	GOSUMDB
 	GOTMPDIR
 	GOTOOLDIR
+	GOVCS
 	GOWASM
 	GO_EXTLINK_ENABLED
 	PKG_CONFIG

tpl/internal/go_templates/fmtsort/sort.go

@@ -130,7 +130,7 @@ func compare(aVal, bVal reflect.Value) int {
 		default:
 			return -1
 		}
-	case reflect.Ptr:
+	case reflect.Ptr, reflect.UnsafePointer:
 		a, b := aVal.Pointer(), bVal.Pointer()
 		switch {
 		case a < b:

tpl/internal/go_templates/fmtsort/sort_test.go

@@ -11,6 +11,7 @@ import (
 	"reflect"
 	"strings"
 	"testing"
+	"unsafe"
 )
 
 var compareTests = [][]reflect.Value{
@@ -32,6 +33,7 @@ var compareTests = [][]reflect.Value{
 	ct(reflect.TypeOf(complex128(0+1i)), -1-1i, -1+0i, -1+1i, 0-1i, 0+0i, 0+1i, 1-1i, 1+0i, 1+1i),
 	ct(reflect.TypeOf(false), false, true),
 	ct(reflect.TypeOf(&ints[0]), &ints[0], &ints[1], &ints[2]),
+	ct(reflect.TypeOf(unsafe.Pointer(&ints[0])), unsafe.Pointer(&ints[0]), unsafe.Pointer(&ints[1]), unsafe.Pointer(&ints[2])),
 	ct(reflect.TypeOf(chans[0]), chans[0], chans[1], chans[2]),
 	ct(reflect.TypeOf(toy{}), toy{0, 1}, toy{0, 2}, toy{1, -1}, toy{1, 1}),
 	ct(reflect.TypeOf([2]int{}), [2]int{1, 1}, [2]int{1, 2}, [2]int{2, 0}),
@@ -118,6 +120,10 @@ var sortTests = []sortTest{
 		pointerMap(),
 		"PTR0:0 PTR1:1 PTR2:2",
 	},
+	{
+		unsafePointerMap(),
+		"UNSAFEPTR0:0 UNSAFEPTR1:1 UNSAFEPTR2:2",
+	},
 	{
 		map[toy]string{{7, 2}: "72", {7, 1}: "71", {3, 4}: "34"},
 		"{3 4}:34 {7 1}:71 {7 2}:72",
@@ -159,6 +165,14 @@ func sprintKey(key reflect.Value) string {
 			}
 		}
 		return "PTR???"
+	case "unsafe.Pointer":
+		ptr := key.Interface().(unsafe.Pointer)
+		for i := range ints {
+			if ptr == unsafe.Pointer(&ints[i]) {
+				return fmt.Sprintf("UNSAFEPTR%d", i)
+			}
+		}
+		return "UNSAFEPTR???"
 	case "chan int":
 		c := key.Interface().(chan int)
 		for i := range chans {
@@ -185,6 +199,14 @@ func pointerMap() map[*int]string {
 	return m
 }
 
+func unsafePointerMap() map[unsafe.Pointer]string {
+	m := make(map[unsafe.Pointer]string)
+	for i := 2; i >= 0; i-- {
+		m[unsafe.Pointer(&ints[i])] = fmt.Sprint(i)
+	}
+	return m
+}
+
 func chanMap() map[chan int]string {
 	m := make(map[chan int]string)
 	for i := 2; i >= 0; i-- {

tpl/internal/go_templates/htmltemplate/clone_test.go

@@ -10,7 +10,7 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"strings"
 	"sync"
 	"testing"
@@ -18,7 +18,7 @@ import (
 	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
 )
 
-func TestAddParseTree(t *testing.T) {
+func TestAddParseTreeHTML(t *testing.T) {
 	root := Must(New("root").Parse(`{{define "a"}} {{.}} {{template "b"}} {{.}} "></a>{{end}}`))
 	tree, err := parse.Parse("t", `{{define "b"}}<a href="{{end}}`, "", "", nil, nil)
 	if err != nil {
@@ -174,7 +174,7 @@ func TestCloneThenParse(t *testing.T) {
 		t.Error("adding a template to a clone added it to the original")
 	}
 	// double check that the embedded template isn't available in the original
-	err := t0.ExecuteTemplate(ioutil.Discard, "a", nil)
+	err := t0.ExecuteTemplate(io.Discard, "a", nil)
 	if err == nil {
 		t.Error("expected 'no such template' error")
 	}
@@ -188,13 +188,13 @@ func TestFuncMapWorksAfterClone(t *testing.T) {
 
 	// get the expected error output (no clone)
 	uncloned := Must(New("").Funcs(funcs).Parse("{{customFunc}}"))
-	wantErr := uncloned.Execute(ioutil.Discard, nil)
+	wantErr := uncloned.Execute(io.Discard, nil)
 
 	// toClone must be the same as uncloned. It has to be recreated from scratch,
 	// since cloning cannot occur after execution.
 	toClone := Must(New("").Funcs(funcs).Parse("{{customFunc}}"))
 	cloned := Must(toClone.Clone())
-	gotErr := cloned.Execute(ioutil.Discard, nil)
+	gotErr := cloned.Execute(io.Discard, nil)
 
 	if wantErr.Error() != gotErr.Error() {
 		t.Errorf("clone error message mismatch want %q got %q", wantErr, gotErr)
@@ -216,7 +216,7 @@ func TestTemplateCloneExecuteRace(t *testing.T) {
 		go func() {
 			defer wg.Done()
 			for i := 0; i < 100; i++ {
-				if err := tmpl.Execute(ioutil.Discard, "data"); err != nil {
+				if err := tmpl.Execute(io.Discard, "data"); err != nil {
 					panic(err)
 				}
 			}
@@ -240,7 +240,7 @@ func TestCloneGrowth(t *testing.T) {
 	tmpl = Must(tmpl.Clone())
 	Must(tmpl.Parse(`{{define "B"}}Text{{end}}`))
 	for i := 0; i < 10; i++ {
-		tmpl.Execute(ioutil.Discard, nil)
+		tmpl.Execute(io.Discard, nil)
 	}
 	if len(tmpl.DefinedTemplates()) > 200 {
 		t.Fatalf("too many templates: %v", len(tmpl.DefinedTemplates()))
@@ -260,7 +260,7 @@ func TestCloneRedefinedName(t *testing.T) {
 	for i := 0; i < 2; i++ {
 		t2 := Must(t1.Clone())
 		t2 = Must(t2.New(fmt.Sprintf("%d", i)).Parse(page))
-		err := t2.Execute(ioutil.Discard, nil)
+		err := t2.Execute(io.Discard, nil)
 		if err != nil {
 			t.Fatal(err)
 		}

tpl/internal/go_templates/htmltemplate/content_test.go

@@ -404,11 +404,11 @@ func TestTypedContent(t *testing.T) {
 }
 
 // Test that we print using the String method. Was issue 3073.
-type stringer struct {
+type myStringer struct {
 	v int
 }
 
-func (s *stringer) String() string {
+func (s *myStringer) String() string {
 	return fmt.Sprintf("string=%d", s.v)
 }
 
@@ -421,7 +421,7 @@ func (s *errorer) Error() string {
 }
 
 func TestStringer(t *testing.T) {
-	s := &stringer{3}
+	s := &myStringer{3}
 	b := new(bytes.Buffer)
 	tmpl := Must(New("x").Parse("{{.}}"))
 	if err := tmpl.Execute(b, s); err != nil {

tpl/internal/go_templates/htmltemplate/escape.go

@@ -125,6 +125,8 @@ func (e *escaper) escape(c context, n parse.Node) context {
 	switch n := n.(type) {
 	case *parse.ActionNode:
 		return e.escapeAction(c, n)
+	case *parse.CommentNode:
+		return c
 	case *parse.IfNode:
 		return e.escapeBranch(c, &n.BranchNode, "if")
 	case *parse.ListNode:

tpl/internal/go_templates/htmltemplate/escape_test.go

@@ -1825,7 +1825,7 @@ func TestIndirectPrint(t *testing.T) {
 }
 
 // This is a test for issue 3272.
-func TestEmptyTemplate(t *testing.T) {
+func TestEmptyTemplateHTML(t *testing.T) {
 	page := Must(New("page").ParseFiles(os.DevNull))
 	if err := page.ExecuteTemplate(os.Stdout, "page", "nothing"); err == nil {
 		t.Fatal("expected error")

tpl/internal/go_templates/htmltemplate/html.go

@@ -240,8 +240,7 @@ func htmlNameFilter(args ...interface{}) string {
 	}
 	s = strings.ToLower(s)
 	if t := attrType(s); t != contentTypePlain {
-		// TODO: Split attr and element name part filters so we can whitelist
+		// TODO: Split attr and element name part filters so we can recognize known attributes.
-		// attributes.
 		return filterFailsafe
 	}
 	for _, r := range s {

tpl/internal/go_templates/htmltemplate/multi_test.go

@@ -0,0 +1,292 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests for multiple-template execution, copied from text/template.
+
+// +build go1.13,!windows
+
+package template
+
+import (
+	"archive/zip"
+	"bytes"
+	"os"
+	"testing"
+
+	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
+)
+
+var multiExecTests = []execTest{
+	{"empty", "", "", nil, true},
+	{"text", "some text", "some text", nil, true},
+	{"invoke x", `{{template "x" .SI}}`, "TEXT", tVal, true},
+	{"invoke x no args", `{{template "x"}}`, "TEXT", tVal, true},
+	{"invoke dot int", `{{template "dot" .I}}`, "17", tVal, true},
+	{"invoke dot []int", `{{template "dot" .SI}}`, "[3 4 5]", tVal, true},
+	{"invoke dotV", `{{template "dotV" .U}}`, "v", tVal, true},
+	{"invoke nested int", `{{template "nested" .I}}`, "17", tVal, true},
+	{"variable declared by template", `{{template "nested" $x:=.SI}},{{index $x 1}}`, "[3 4 5],4", tVal, true},
+
+	// User-defined function: test argument evaluator.
+	{"testFunc literal", `{{oneArg "joe"}}`, "oneArg=joe", tVal, true},
+	{"testFunc .", `{{oneArg .}}`, "oneArg=joe", "joe", true},
+}
+
+// These strings are also in testdata/*.
+const multiText1 = `
+	{{define "x"}}TEXT{{end}}
+	{{define "dotV"}}{{.V}}{{end}}
+`
+
+const multiText2 = `
+	{{define "dot"}}{{.}}{{end}}
+	{{define "nested"}}{{template "dot" .}}{{end}}
+`
+
+func TestMultiExecute(t *testing.T) {
+	// Declare a couple of templates first.
+	template, err := New("root").Parse(multiText1)
+	if err != nil {
+		t.Fatalf("parse error for 1: %s", err)
+	}
+	_, err = template.Parse(multiText2)
+	if err != nil {
+		t.Fatalf("parse error for 2: %s", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+func TestParseFiles(t *testing.T) {
+	_, err := ParseFiles("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	template := New("root")
+	_, err = template.ParseFiles("testdata/file1.tmpl", "testdata/file2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+func TestParseGlob(t *testing.T) {
+	_, err := ParseGlob("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	_, err = New("error").ParseGlob("[x")
+	if err == nil {
+		t.Error("expected error for bad pattern; got none")
+	}
+	template := New("root")
+	_, err = template.ParseGlob("testdata/file*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+func TestParseFS(t *testing.T) {
+	fs := os.DirFS("testdata")
+
+	{
+		_, err := ParseFS(fs, "DOES NOT EXIST")
+		if err == nil {
+			t.Error("expected error for non-existent file; got none")
+		}
+	}
+
+	{
+		template := New("root")
+		_, err := template.ParseFS(fs, "file1.tmpl", "file2.tmpl")
+		if err != nil {
+			t.Fatalf("error parsing files: %v", err)
+		}
+		testExecute(multiExecTests, template, t)
+	}
+
+	{
+		template := New("root")
+		_, err := template.ParseFS(fs, "file*.tmpl")
+		if err != nil {
+			t.Fatalf("error parsing files: %v", err)
+		}
+		testExecute(multiExecTests, template, t)
+	}
+}
+
+// In these tests, actual content (not just template definitions) comes from the parsed files.
+
+var templateFileExecTests = []execTest{
+	{"test", `{{template "tmpl1.tmpl"}}{{template "tmpl2.tmpl"}}`, "template1\n\ny\ntemplate2\n\nx\n", 0, true},
+}
+
+func TestParseFilesWithData(t *testing.T) {
+	template, err := New("root").ParseFiles("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, template, t)
+}
+
+func TestParseGlobWithData(t *testing.T) {
+	template, err := New("root").ParseGlob("testdata/tmpl*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, template, t)
+}
+
+func TestParseZipFS(t *testing.T) {
+	z, err := zip.OpenReader("testdata/fs.zip")
+	if err != nil {
+		t.Fatalf("error parsing zip: %v", err)
+	}
+	template, err := New("root").ParseFS(z, "tmpl*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, template, t)
+}
+
+const (
+	cloneText1 = `{{define "a"}}{{template "b"}}{{template "c"}}{{end}}`
+	cloneText2 = `{{define "b"}}b{{end}}`
+	cloneText3 = `{{define "c"}}root{{end}}`
+	cloneText4 = `{{define "c"}}clone{{end}}`
+)
+
+// Issue 7032
+func TestAddParseTreeToUnparsedTemplate(t *testing.T) {
+	master := "{{define \"master\"}}{{end}}"
+	tmpl := New("master")
+	tree, err := parse.Parse("master", master, "", "", nil)
+	if err != nil {
+		t.Fatalf("unexpected parse err: %v", err)
+	}
+	masterTree := tree["master"]
+	tmpl.AddParseTree("master", masterTree) // used to panic
+}
+
+func TestRedefinition(t *testing.T) {
+	var tmpl *Template
+	var err error
+	if tmpl, err = New("tmpl1").Parse(`{{define "test"}}foo{{end}}`); err != nil {
+		t.Fatalf("parse 1: %v", err)
+	}
+	if _, err = tmpl.Parse(`{{define "test"}}bar{{end}}`); err != nil {
+		t.Fatalf("got error %v, expected nil", err)
+	}
+	if _, err = tmpl.New("tmpl2").Parse(`{{define "test"}}bar{{end}}`); err != nil {
+		t.Fatalf("got error %v, expected nil", err)
+	}
+}
+
+// Issue 10879
+func TestEmptyTemplateCloneCrash(t *testing.T) {
+	t1 := New("base")
+	t1.Clone() // used to panic
+}
+
+// Issue 10910, 10926
+func TestTemplateLookUp(t *testing.T) {
+	t.Skip("broken on html/template") // TODO
+	t1 := New("foo")
+	if t1.Lookup("foo") != nil {
+		t.Error("Lookup returned non-nil value for undefined template foo")
+	}
+	t1.New("bar")
+	if t1.Lookup("bar") != nil {
+		t.Error("Lookup returned non-nil value for undefined template bar")
+	}
+	t1.Parse(`{{define "foo"}}test{{end}}`)
+	if t1.Lookup("foo") == nil {
+		t.Error("Lookup returned nil value for defined template")
+	}
+}
+
+func TestParse(t *testing.T) {
+	// In multiple calls to Parse with the same receiver template, only one call
+	// can contain text other than space, comments, and template definitions
+	t1 := New("test")
+	if _, err := t1.Parse(`{{define "test"}}{{end}}`); err != nil {
+		t.Fatalf("parsing test: %s", err)
+	}
+	if _, err := t1.Parse(`{{define "test"}}{{/* this is a comment */}}{{end}}`); err != nil {
+		t.Fatalf("parsing test: %s", err)
+	}
+	if _, err := t1.Parse(`{{define "test"}}foo{{end}}`); err != nil {
+		t.Fatalf("parsing test: %s", err)
+	}
+}
+
+func TestEmptyTemplate(t *testing.T) {
+	cases := []struct {
+		defn []string
+		in   string
+		want string
+	}{
+		{[]string{"x", "y"}, "", "y"},
+		{[]string{""}, "once", ""},
+		{[]string{"", ""}, "twice", ""},
+		{[]string{"{{.}}", "{{.}}"}, "twice", "twice"},
+		{[]string{"{{/* a comment */}}", "{{/* a comment */}}"}, "comment", ""},
+		{[]string{"{{.}}", ""}, "twice", "twice"}, // TODO: should want "" not "twice"
+	}
+
+	for i, c := range cases {
+		root := New("root")
+
+		var (
+			m   *Template
+			err error
+		)
+		for _, d := range c.defn {
+			m, err = root.New(c.in).Parse(d)
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
+		buf := &bytes.Buffer{}
+		if err := m.Execute(buf, c.in); err != nil {
+			t.Error(i, err)
+			continue
+		}
+		if buf.String() != c.want {
+			t.Errorf("expected string %q: got %q", c.want, buf.String())
+		}
+	}
+}
+
+// Issue 19249 was a regression in 1.8 caused by the handling of empty
+// templates added in that release, which got different answers depending
+// on the order templates appeared in the internal map.
+func TestIssue19294(t *testing.T) {
+	// The empty block in "xhtml" should be replaced during execution
+	// by the contents of "stylesheet", but if the internal map associating
+	// names with templates is built in the wrong order, the empty block
+	// looks non-empty and this doesn't happen.
+	var inlined = map[string]string{
+		"stylesheet": `{{define "stylesheet"}}stylesheet{{end}}`,
+		"xhtml":      `{{block "stylesheet" .}}{{end}}`,
+	}
+	all := []string{"stylesheet", "xhtml"}
+	for i := 0; i < 100; i++ {
+		res, err := New("title.xhtml").Parse(`{{template "xhtml" .}}`)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, name := range all {
+			_, err := res.New(name).Parse(inlined[name])
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
+		var buf bytes.Buffer
+		res.Execute(&buf, 0)
+		if buf.String() != "stylesheet" {
+			t.Fatalf("iteration %d: got %q; expected %q", i, buf.String(), "stylesheet")
+		}
+	}
+}

tpl/internal/go_templates/htmltemplate/template.go

@@ -7,7 +7,9 @@ package template
 import (
 	"fmt"
 	"io"
+	"io/fs"
 	"io/ioutil"
+	"path"
 	"path/filepath"
 	"sync"
 
@@ -385,7 +387,7 @@ func Must(t *Template, err error) *Template {
 // For instance, ParseFiles("a/foo", "b/foo") stores "b/foo" as the template
 // named "foo", while "a/foo" is unavailable.
 func ParseFiles(filenames ...string) (*Template, error) {
-	return parseFiles(nil, filenames...)
+	return parseFiles(nil, readFileOS, filenames...)
 }
 
 // ParseFiles parses the named files and associates the resulting templates with
@@ -397,12 +399,12 @@ func ParseFiles(filenames ...string) (*Template, error) {
 //
 // ParseFiles returns an error if t or any associated template has already been executed.
 func (t *Template) ParseFiles(filenames ...string) (*Template, error) {
-	return parseFiles(t, filenames...)
+	return parseFiles(t, readFileOS, filenames...)
 }
 
 // parseFiles is the helper for the method and function. If the argument
 // template is nil, it is created from the first file.
-func parseFiles(t *Template, filenames ...string) (*Template, error) {
+func parseFiles(t *Template, readFile func(string) (string, []byte, error), filenames ...string) (*Template, error) {
 	if err := t.checkCanParse(); err != nil {
 		return nil, err
 	}
@@ -412,12 +414,11 @@ func parseFiles(t *Template, filenames ...string) (*Template, error) {
 		return nil, fmt.Errorf("html/template: no files named in call to ParseFiles")
 	}
 	for _, filename := range filenames {
-		b, err := ioutil.ReadFile(filename)
+		name, b, err := readFile(filename)
 		if err != nil {
 			return nil, err
 		}
 		s := string(b)
-		name := filepath.Base(filename)
 		// First template becomes return value if not already defined,
 		// and we use that one for subsequent New calls to associate
 		// all the templates together. Also, if this file has the same name
@@ -480,7 +481,7 @@ func parseGlob(t *Template, pattern string) (*Template, error) {
 	if len(filenames) == 0 {
 		return nil, fmt.Errorf("html/template: pattern matches no files: %#q", pattern)
 	}
-	return parseFiles(t, filenames...)
+	return parseFiles(t, readFileOS, filenames...)
 }
 
 // IsTrue reports whether the value is 'true', in the sense of not the zero of its type,
@@ -489,3 +490,48 @@ func parseGlob(t *Template, pattern string) (*Template, error) {
 func IsTrue(val interface{}) (truth, ok bool) {
 	return template.IsTrue(val)
 }
+
+// ParseFS is like ParseFiles or ParseGlob but reads from the file system fs
+// instead of the host operating system's file system.
+// It accepts a list of glob patterns.
+// (Note that most file names serve as glob patterns matching only themselves.)
+func ParseFS(fs fs.FS, patterns ...string) (*Template, error) {
+	return parseFS(nil, fs, patterns)
+}
+
+// ParseFS is like ParseFiles or ParseGlob but reads from the file system fs
+// instead of the host operating system's file system.
+// It accepts a list of glob patterns.
+// (Note that most file names serve as glob patterns matching only themselves.)
+func (t *Template) ParseFS(fs fs.FS, patterns ...string) (*Template, error) {
+	return parseFS(t, fs, patterns)
+}
+
+func parseFS(t *Template, fsys fs.FS, patterns []string) (*Template, error) {
+	var filenames []string
+	for _, pattern := range patterns {
+		list, err := fs.Glob(fsys, pattern)
+		if err != nil {
+			return nil, err
+		}
+		if len(list) == 0 {
+			return nil, fmt.Errorf("template: pattern matches no files: %#q", pattern)
+		}
+		filenames = append(filenames, list...)
+	}
+	return parseFiles(t, readFileFS(fsys), filenames...)
+}
+
+func readFileOS(file string) (name string, b []byte, err error) {
+	name = filepath.Base(file)
+	b, err = ioutil.ReadFile(file)
+	return
+}
+
+func readFileFS(fsys fs.FS) func(string) (string, []byte, error) {
+	return func(file string) (name string, b []byte, err error) {
+		name = path.Base(file)
+		b, err = fs.ReadFile(fsys, file)
+		return
+	}
+}

tpl/internal/go_templates/htmltemplate/template_test.go

@@ -13,10 +13,11 @@ import (
 	"testing"
 
 	. "github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"
+	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse" // https://golang.org/issue/12996
 )
 
 func TestTemplateClone(t *testing.T) {
-	// https://golang.org/issue/12996
+
 	orig := New("name")
 	clone, err := orig.Clone()
 	if err != nil {
@@ -163,6 +164,21 @@ func TestStringsInScriptsWithJsonContentTypeAreCorrectlyEscaped(t *testing.T) {
 	}
 }
 
+func TestSkipEscapeComments(t *testing.T) {
+	c := newTestCase(t)
+	tr := parse.New("root")
+	tr.Mode = parse.ParseComments
+	newT, err := tr.Parse("{{/* A comment */}}{{ 1 }}{{/* Another comment */}}", "", "", make(map[string]*parse.Tree))
+	if err != nil {
+		t.Fatalf("Cannot parse template text: %v", err)
+	}
+	c.root, err = c.root.AddParseTree("root", newT)
+	if err != nil {
+		t.Fatalf("Cannot add parse tree to template: %v", err)
+	}
+	c.mustExecute(c.root, nil, "1")
+}
+
 type testCase struct {
 	t    *testing.T
 	root *Template

tpl/internal/go_templates/testenv/testenv.go

@@ -45,12 +45,8 @@ func HasGoBuild() bool {
 		return false
 	}
 	switch runtime.GOOS {
-	case "android", "js":
+	case "android", "js", "ios":
 		return false
-	case "darwin":
-		if runtime.GOARCH == "arm64" {
-			return false
-		}
 	}
 	return true
 }
@@ -124,12 +120,8 @@ func GoTool() (string, error) {
 // using os.StartProcess or (more commonly) exec.Command.
 func HasExec() bool {
 	switch runtime.GOOS {
-	case "js":
+	case "js", "ios":
 		return false
-	case "darwin":
-		if runtime.GOARCH == "arm64" {
-			return false
-		}
 	}
 	return true
 }
@@ -137,10 +129,8 @@ func HasExec() bool {
 // HasSrc reports whether the entire source tree is available under GOROOT.
 func HasSrc() bool {
 	switch runtime.GOOS {
-	case "darwin":
+	case "ios":
-		if runtime.GOARCH == "arm64" {
+		return false
-			return false
-		}
 	}
 	return true
 }
@@ -204,6 +194,32 @@ func MustHaveCGO(t testing.TB) {
 	}
 }
 
+// CanInternalLink reports whether the current system can link programs with
+// internal linking.
+// (This is the opposite of cmd/internal/sys.MustLinkExternal. Keep them in sync.)
+func CanInternalLink() bool {
+	switch runtime.GOOS {
+	case "android":
+		if runtime.GOARCH != "arm64" {
+			return false
+		}
+	case "ios":
+		if runtime.GOARCH == "arm64" {
+			return false
+		}
+	}
+	return true
+}
+
+// MustInternalLink checks that the current system can link programs with internal
+// linking.
+// If not, MustInternalLink calls t.Skip with an explanation.
+func MustInternalLink(t testing.TB) {
+	if !CanInternalLink() {
+		t.Skipf("skipping test: internal linking on %s/%s is not supported", runtime.GOOS, runtime.GOARCH)
+	}
+}
+
 // HasSymlink reports whether the current system can use os.Symlink.
 func HasSymlink() bool {
 	ok, _ := hasSymlink()
@@ -272,3 +288,23 @@ func CleanCmdEnv(cmd *exec.Cmd) *exec.Cmd {
 	}
 	return cmd
 }
+
+// CPUIsSlow reports whether the CPU running the test is suspected to be slow.
+func CPUIsSlow() bool {
+	switch runtime.GOARCH {
+	case "arm", "mips", "mipsle", "mips64", "mips64le":
+		return true
+	}
+	return false
+}
+
+// SkipIfShortAndSlow skips t if -short is set and the CPU running the test is
+// suspected to be slow.
+//
+// (This is useful for CPU-intensive tests that otherwise complete quickly.)
+func SkipIfShortAndSlow(t testing.TB) {
+	if testing.Short() && CPUIsSlow() {
+		t.Helper()
+		t.Skipf("skipping test in -short mode on %s", runtime.GOARCH)
+	}
+}

tpl/internal/go_templates/texttemplate/doc.go

@@ -40,16 +40,17 @@ More intricate examples appear below.
 Text and spaces
 
 By default, all text between actions is copied verbatim when the template is
-executed. For example, the string " items are made of " in the example above appears
+executed. For example, the string " items are made of " in the example above
-on standard output when the program is run.
+appears on standard output when the program is run.
 
-However, to aid in formatting template source code, if an action's left delimiter
+However, to aid in formatting template source code, if an action's left
-(by default "{{") is followed immediately by a minus sign and ASCII space character
+delimiter (by default "{{") is followed immediately by a minus sign and white
-("{{- "), all trailing white space is trimmed from the immediately preceding text.
+space, all trailing white space is trimmed from the immediately preceding text.
-Similarly, if the right delimiter ("}}") is preceded by a space and minus sign
+Similarly, if the right delimiter ("}}") is preceded by white space and a minus
-(" -}}"), all leading white space is trimmed from the immediately following text.
+sign, all leading white space is trimmed from the immediately following text.
-In these trim markers, the ASCII space must be present; "{{-3}}" parses as an
+In these trim markers, the white space must be present:
-action containing the number -3.
+"{{- 3}}" is like "{{3}}" but trims the immediately preceding text, while
+"{{-3}}" parses as an action containing the number -3.
 
 For instance, when executing the template whose source is
 

tpl/internal/go_templates/texttemplate/exec.go

@@ -256,6 +256,7 @@ func (s *state) walk(dot reflect.Value, node parse.Node) {
 		if len(node.Pipe.Decl) == 0 {
 			s.printValue(node, val)
 		}
+	case *parse.CommentNode:
 	case *parse.IfNode:
 		s.walkIfOrWith(parse.NodeIf, dot, node.Pipe, node.List, node.ElseList)
 	case *parse.ListNode:

tpl/internal/go_templates/texttemplate/exec_test.go

@@ -11,7 +11,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"reflect"
 	"strings"
 	"testing"
@@ -1297,7 +1297,7 @@ func TestUnterminatedStringError(t *testing.T) {
 		t.Fatal("expected error")
 	}
 	str := err.Error()
-	if !strings.Contains(str, "X:3: unexpected unterminated raw quoted string") {
+	if !strings.Contains(str, "X:3: unterminated raw quoted string") {
 		t.Fatalf("unexpected error: %s", str)
 	}
 }
@@ -1330,7 +1330,7 @@ func TestExecuteGivesExecError(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	err = tmpl.Execute(ioutil.Discard, 0)
+	err = tmpl.Execute(io.Discard, 0)
 	if err == nil {
 		t.Fatal("expected error; got none")
 	}
@@ -1476,7 +1476,7 @@ func TestEvalFieldErrors(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			tmpl := Must(New("tmpl").Parse(tc.src))
-			err := tmpl.Execute(ioutil.Discard, tc.value)
+			err := tmpl.Execute(io.Discard, tc.value)
 			got := "<nil>"
 			if err != nil {
 				got = err.Error()
@@ -1493,7 +1493,7 @@ func TestMaxExecDepth(t *testing.T) {
 		t.Skip("skipping in -short mode")
 	}
 	tmpl := Must(New("tmpl").Parse(`{{template "tmpl" .}}`))
-	err := tmpl.Execute(ioutil.Discard, nil)
+	err := tmpl.Execute(io.Discard, nil)
 	got := "<nil>"
 	if err != nil {
 		got = err.Error()

tpl/internal/go_templates/texttemplate/helper.go

@@ -8,7 +8,9 @@ package template
 
 import (
 	"fmt"
+	"io/fs"
 	"io/ioutil"
+	"path"
 	"path/filepath"
 )
 
@@ -35,7 +37,7 @@ func Must(t *Template, err error) *Template {
 // For instance, ParseFiles("a/foo", "b/foo") stores "b/foo" as the template
 // named "foo", while "a/foo" is unavailable.
 func ParseFiles(filenames ...string) (*Template, error) {
-	return parseFiles(nil, filenames...)
+	return parseFiles(nil, readFileOS, filenames...)
 }
 
 // ParseFiles parses the named files and associates the resulting templates with
@@ -51,23 +53,22 @@ func ParseFiles(filenames ...string) (*Template, error) {
 // the last one mentioned will be the one that results.
 func (t *Template) ParseFiles(filenames ...string) (*Template, error) {
 	t.init()
-	return parseFiles(t, filenames...)
+	return parseFiles(t, readFileOS, filenames...)
 }
 
 // parseFiles is the helper for the method and function. If the argument
 // template is nil, it is created from the first file.
-func parseFiles(t *Template, filenames ...string) (*Template, error) {
+func parseFiles(t *Template, readFile func(string) (string, []byte, error), filenames ...string) (*Template, error) {
 	if len(filenames) == 0 {
 		// Not really a problem, but be consistent.
 		return nil, fmt.Errorf("template: no files named in call to ParseFiles")
 	}
 	for _, filename := range filenames {
-		b, err := ioutil.ReadFile(filename)
+		name, b, err := readFile(filename)
 		if err != nil {
 			return nil, err
 		}
 		s := string(b)
-		name := filepath.Base(filename)
 		// First template becomes return value if not already defined,
 		// and we use that one for subsequent New calls to associate
 		// all the templates together. Also, if this file has the same name
@@ -126,5 +127,51 @@ func parseGlob(t *Template, pattern string) (*Template, error) {
 	if len(filenames) == 0 {
 		return nil, fmt.Errorf("template: pattern matches no files: %#q", pattern)
 	}
-	return parseFiles(t, filenames...)
+	return parseFiles(t, readFileOS, filenames...)
+}
+
+// ParseFS is like ParseFiles or ParseGlob but reads from the file system fsys
+// instead of the host operating system's file system.
+// It accepts a list of glob patterns.
+// (Note that most file names serve as glob patterns matching only themselves.)
+func ParseFS(fsys fs.FS, patterns ...string) (*Template, error) {
+	return parseFS(nil, fsys, patterns)
+}
+
+// ParseFS is like ParseFiles or ParseGlob but reads from the file system fsys
+// instead of the host operating system's file system.
+// It accepts a list of glob patterns.
+// (Note that most file names serve as glob patterns matching only themselves.)
+func (t *Template) ParseFS(fsys fs.FS, patterns ...string) (*Template, error) {
+	t.init()
+	return parseFS(t, fsys, patterns)
+}
+
+func parseFS(t *Template, fsys fs.FS, patterns []string) (*Template, error) {
+	var filenames []string
+	for _, pattern := range patterns {
+		list, err := fs.Glob(fsys, pattern)
+		if err != nil {
+			return nil, err
+		}
+		if len(list) == 0 {
+			return nil, fmt.Errorf("template: pattern matches no files: %#q", pattern)
+		}
+		filenames = append(filenames, list...)
+	}
+	return parseFiles(t, readFileFS(fsys), filenames...)
+}
+
+func readFileOS(file string) (name string, b []byte, err error) {
+	name = filepath.Base(file)
+	b, err = ioutil.ReadFile(file)
+	return
+}
+
+func readFileFS(fsys fs.FS) func(string) (string, []byte, error) {
+	return func(file string) (name string, b []byte, err error) {
+		name = path.Base(file)
+		b, err = fs.ReadFile(fsys, file)
+		return
+	}
 }

tpl/internal/go_templates/texttemplate/link_test.go

@@ -0,0 +1,66 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.13
+
+package template_test
+
+import (
+	"bytes"
+	"github.com/gohugoio/hugo/tpl/internal/go_templates/testenv"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+// Issue 36021: verify that text/template doesn't prevent the linker from removing
+// unused methods.
+func _TestLinkerGC(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+	testenv.MustHaveGoBuild(t)
+	const prog = `package main
+
+import (
+	_ "text/template"
+)
+
+type T struct{}
+
+func (t *T) Unused() { println("THIS SHOULD BE ELIMINATED") }
+func (t *T) Used() {}
+
+var sink *T
+
+func main() {
+	var t T
+	sink = &t
+	t.Used()
+}
+`
+	td, err := ioutil.TempDir("", "text_template_TestDeadCodeElimination")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(td)
+
+	if err := ioutil.WriteFile(filepath.Join(td, "x.go"), []byte(prog), 0644); err != nil {
+		t.Fatal(err)
+	}
+	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", "x.exe", "x.go")
+	cmd.Dir = td
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("go build: %v, %s", err, out)
+	}
+	slurp, err := ioutil.ReadFile(filepath.Join(td, "x.exe"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if bytes.Contains(slurp, []byte("THIS SHOULD BE ELIMINATED")) {
+		t.Error("binary contains code that should be deadcode eliminated")
+	}
+}

tpl/internal/go_templates/texttemplate/multi_test.go

@@ -12,6 +12,7 @@ import (
 	"bytes"
 	"fmt"
 	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
+	"os"
 	"testing"
 )
 
@@ -155,6 +156,35 @@ func TestParseGlob(t *testing.T) {
 	testExecute(multiExecTests, template, t)
 }
 
+func TestParseFS(t *testing.T) {
+	fs := os.DirFS("testdata")
+
+	{
+		_, err := ParseFS(fs, "DOES NOT EXIST")
+		if err == nil {
+			t.Error("expected error for non-existent file; got none")
+		}
+	}
+
+	{
+		template := New("root")
+		_, err := template.ParseFS(fs, "file1.tmpl", "file2.tmpl")
+		if err != nil {
+			t.Fatalf("error parsing files: %v", err)
+		}
+		testExecute(multiExecTests, template, t)
+	}
+
+	{
+		template := New("root")
+		_, err := template.ParseFS(fs, "file*.tmpl")
+		if err != nil {
+			t.Fatalf("error parsing files: %v", err)
+		}
+		testExecute(multiExecTests, template, t)
+	}
+}
+
 // In these tests, actual content (not just template definitions) comes from the parsed files.
 
 var templateFileExecTests = []execTest{
@@ -361,6 +391,7 @@ func TestEmptyTemplate(t *testing.T) {
 		in   string
 		want string
 	}{
+		{[]string{"x", "y"}, "", "y"},
 		{[]string{""}, "once", ""},
 		{[]string{"", ""}, "twice", ""},
 		{[]string{"{{.}}", "{{.}}"}, "twice", "twice"},

tpl/internal/go_templates/texttemplate/parse/lex.go

@@ -41,6 +41,7 @@ const (
 	itemBool                         // boolean constant
 	itemChar                         // printable ASCII character; grab bag for comma etc.
 	itemCharConstant                 // character constant
+	itemComment                      // comment text
 	itemComplex                      // complex constant (1+2i); imaginary is just a number
 	itemAssign                       // equals ('=') introducing an assignment
 	itemDeclare                      // colon-equals (':=') introducing a declaration
@@ -91,15 +92,14 @@ const eof = -1
 // If the action begins "{{- " rather than "{{", then all space/tab/newlines
 // preceding the action are trimmed; conversely if it ends " -}}" the
 // leading spaces are trimmed. This is done entirely in the lexer; the
-// parser never sees it happen. We require an ASCII space to be
+// parser never sees it happen. We require an ASCII space (' ', \t, \r, \n)
-// present to avoid ambiguity with things like "{{-3}}". It reads
+// to be present to avoid ambiguity with things like "{{-3}}". It reads
 // better with the space present anyway. For simplicity, only ASCII
-// space does the job.
+// does the job.
 const (
-	spaceChars      = " \t\r\n" // These are the space characters defined by Go itself.
+	spaceChars    = " \t\r\n"  // These are the space characters defined by Go itself.
-	leftTrimMarker  = "- "      // Attached to left delimiter, trims trailing spaces from preceding text.
+	trimMarker    = '-'        // Attached to left/right delimiter, trims trailing spaces from preceding/following text.
-	rightTrimMarker = " -"      // Attached to right delimiter, trims leading spaces from following text.
+	trimMarkerLen = Pos(1 + 1) // marker plus space before or after
-	trimMarkerLen   = Pos(len(leftTrimMarker))
 )
 
 // stateFn represents the state of the scanner as a function that returns the next state.
@@ -107,18 +107,18 @@ type stateFn func(*lexer) stateFn
 
 // lexer holds the state of the scanner.
 type lexer struct {
-	name           string    // the name of the input; used only for error reports
+	name        string    // the name of the input; used only for error reports
-	input          string    // the string being scanned
+	input       string    // the string being scanned
-	leftDelim      string    // start of action
+	leftDelim   string    // start of action
-	rightDelim     string    // end of action
+	rightDelim  string    // end of action
-	trimRightDelim string    // end of action with trim marker
+	emitComment bool      // emit itemComment tokens.
-	pos            Pos       // current position in the input
+	pos         Pos       // current position in the input
-	start          Pos       // start position of this item
+	start       Pos       // start position of this item
-	width          Pos       // width of last rune read from input
+	width       Pos       // width of last rune read from input
-	items          chan item // channel of scanned items
+	items       chan item // channel of scanned items
-	parenDepth     int       // nesting depth of ( ) exprs
+	parenDepth  int       // nesting depth of ( ) exprs
-	line           int       // 1+number of newlines seen
+	line        int       // 1+number of newlines seen
-	startLine      int       // start line of this item
+	startLine   int       // start line of this item
 }
 
 // next returns the next rune in the input.
@@ -203,7 +203,7 @@ func (l *lexer) drain() {
 }
 
 // lex creates a new scanner for the input string.
-func lex(name, input, left, right string) *lexer {
+func lex(name, input, left, right string, emitComment bool) *lexer {
 	if left == "" {
 		left = leftDelim
 	}
@@ -211,14 +211,14 @@ func lex(name, input, left, right string) *lexer {
 		right = rightDelim
 	}
 	l := &lexer{
-		name:           name,
+		name:        name,
-		input:          input,
+		input:       input,
-		leftDelim:      left,
+		leftDelim:   left,
-		rightDelim:     right,
+		rightDelim:  right,
-		trimRightDelim: rightTrimMarker + right,
+		emitComment: emitComment,
-		items:          make(chan item),
+		items:       make(chan item),
-		line:           1,
+		line:        1,
-		startLine:      1,
+		startLine:   1,
 	}
 	go l.run()
 	return l
@@ -248,7 +248,7 @@ func lexText(l *lexer) stateFn {
 		ldn := Pos(len(l.leftDelim))
 		l.pos += Pos(x)
 		trimLength := Pos(0)
-		if strings.HasPrefix(l.input[l.pos+ldn:], leftTrimMarker) {
+		if hasLeftTrimMarker(l.input[l.pos+ldn:]) {
 			trimLength = rightTrimLength(l.input[l.start:l.pos])
 		}
 		l.pos -= trimLength
@@ -277,7 +277,7 @@ func rightTrimLength(s string) Pos {
 
 // atRightDelim reports whether the lexer is at a right delimiter, possibly preceded by a trim marker.
 func (l *lexer) atRightDelim() (delim, trimSpaces bool) {
-	if strings.HasPrefix(l.input[l.pos:], l.trimRightDelim) { // With trim marker.
+	if hasRightTrimMarker(l.input[l.pos:]) && strings.HasPrefix(l.input[l.pos+trimMarkerLen:], l.rightDelim) { // With trim marker.
 		return true, true
 	}
 	if strings.HasPrefix(l.input[l.pos:], l.rightDelim) { // Without trim marker.
@@ -294,7 +294,7 @@ func leftTrimLength(s string) Pos {
 // lexLeftDelim scans the left delimiter, which is known to be present, possibly with a trim marker.
 func lexLeftDelim(l *lexer) stateFn {
 	l.pos += Pos(len(l.leftDelim))
-	trimSpace := strings.HasPrefix(l.input[l.pos:], leftTrimMarker)
+	trimSpace := hasLeftTrimMarker(l.input[l.pos:])
 	afterMarker := Pos(0)
 	if trimSpace {
 		afterMarker = trimMarkerLen
@@ -323,6 +323,9 @@ func lexComment(l *lexer) stateFn {
 	if !delim {
 		return l.errorf("comment ends before closing delimiter")
 	}
+	if l.emitComment {
+		l.emit(itemComment)
+	}
 	if trimSpace {
 		l.pos += trimMarkerLen
 	}
@@ -336,7 +339,7 @@ func lexComment(l *lexer) stateFn {
 
 // lexRightDelim scans the right delimiter, which is known to be present, possibly with a trim marker.
 func lexRightDelim(l *lexer) stateFn {
-	trimSpace := strings.HasPrefix(l.input[l.pos:], rightTrimMarker)
+	trimSpace := hasRightTrimMarker(l.input[l.pos:])
 	if trimSpace {
 		l.pos += trimMarkerLen
 		l.ignore()
@@ -363,7 +366,7 @@ func lexInsideAction(l *lexer) stateFn {
 		return l.errorf("unclosed left paren")
 	}
 	switch r := l.next(); {
-	case r == eof || isEndOfLine(r):
+	case r == eof:
 		return l.errorf("unclosed action")
 	case isSpace(r):
 		l.backup() // Put space back in case we have " -}}".
@@ -433,7 +436,7 @@ func lexSpace(l *lexer) stateFn {
 	}
 	// Be careful about a trim-marked closing delimiter, which has a minus
 	// after a space. We know there is a space, so check for the '-' that might follow.
-	if strings.HasPrefix(l.input[l.pos-1:], l.trimRightDelim) {
+	if hasRightTrimMarker(l.input[l.pos-1:]) && strings.HasPrefix(l.input[l.pos-1+trimMarkerLen:], l.rightDelim) {
 		l.backup() // Before the space.
 		if numSpaces == 1 {
 			return lexRightDelim // On the delim, so go right to that.
@@ -520,7 +523,7 @@ func lexFieldOrVariable(l *lexer, typ itemType) stateFn {
 // day to implement arithmetic.
 func (l *lexer) atTerminator() bool {
 	r := l.peek()
-	if isSpace(r) || isEndOfLine(r) {
+	if isSpace(r) {
 		return true
 	}
 	switch r {
@@ -651,15 +654,18 @@ Loop:
 
 // isSpace reports whether r is a space character.
 func isSpace(r rune) bool {
-	return r == ' ' || r == '\t'
+	return r == ' ' || r == '\t' || r == '\r' || r == '\n'
-}
-
-// isEndOfLine reports whether r is an end-of-line character.
-func isEndOfLine(r rune) bool {
-	return r == '\r' || r == '\n'
 }
 
 // isAlphaNumeric reports whether r is an alphabetic, digit, or underscore.
 func isAlphaNumeric(r rune) bool {
 	return r == '_' || unicode.IsLetter(r) || unicode.IsDigit(r)
 }
+
+func hasLeftTrimMarker(s string) bool {
+	return len(s) >= 2 && s[0] == trimMarker && isSpace(rune(s[1]))
+}
+
+func hasRightTrimMarker(s string) bool {
+	return len(s) >= 2 && isSpace(rune(s[0])) && s[1] == trimMarker
+}

tpl/internal/go_templates/texttemplate/parse/lex_test.go

@@ -17,6 +17,7 @@ var itemName = map[itemType]string{
 	itemBool:         "bool",
 	itemChar:         "char",
 	itemCharConstant: "charconst",
+	itemComment:      "comment",
 	itemComplex:      "complex",
 	itemDeclare:      ":=",
 	itemEOF:          "EOF",
@@ -92,6 +93,7 @@ var lexTests = []lexTest{
 	{"text", `now is the time`, []item{mkItem(itemText, "now is the time"), tEOF}},
 	{"text with comment", "hello-{{/* this is a comment */}}-world", []item{
 		mkItem(itemText, "hello-"),
+		mkItem(itemComment, "/* this is a comment */"),
 		mkItem(itemText, "-world"),
 		tEOF,
 	}},
@@ -313,6 +315,7 @@ var lexTests = []lexTest{
 	}},
 	{"trimming spaces before and after comment", "hello- {{- /* hello */ -}} -world", []item{
 		mkItem(itemText, "hello-"),
+		mkItem(itemComment, "/* hello */"),
 		mkItem(itemText, "-world"),
 		tEOF,
 	}},
@@ -322,7 +325,7 @@ var lexTests = []lexTest{
 		tLeft,
 		mkItem(itemError, "unrecognized character in action: U+0001"),
 	}},
-	{"unclosed action", "{{\n}}", []item{
+	{"unclosed action", "{{", []item{
 		tLeft,
 		mkItem(itemError, "unclosed action"),
 	}},
@@ -391,7 +394,7 @@ var lexTests = []lexTest{
 
 // collect gathers the emitted items into a slice.
 func collect(t *lexTest, left, right string) (items []item) {
-	l := lex(t.name, t.input, left, right)
+	l := lex(t.name, t.input, left, right, true)
 	for {
 		item := l.nextItem()
 		items = append(items, item)
@@ -531,7 +534,7 @@ func TestPos(t *testing.T) {
 func TestShutdown(t *testing.T) {
 	// We need to duplicate template.Parse here to hold on to the lexer.
 	const text = "erroneous{{define}}{{else}}1234"
-	lexer := lex("foo", text, "{{", "}}")
+	lexer := lex("foo", text, "{{", "}}", false)
 	_, err := New("root").parseLexer(lexer)
 	if err == nil {
 		t.Fatalf("expected error")

tpl/internal/go_templates/texttemplate/parse/node.go

@@ -70,6 +70,7 @@ const (
 	NodeTemplate                   // A template invocation action.
 	NodeVariable                   // A $ variable.
 	NodeWith                       // A with action.
+	NodeComment                    // A comment.
 )
 
 // Nodes.
@@ -149,6 +150,38 @@ func (t *TextNode) Copy() Node {
 	return &TextNode{tr: t.tr, NodeType: NodeText, Pos: t.Pos, Text: append([]byte{}, t.Text...)}
 }
 
+// CommentNode holds a comment.
+type CommentNode struct {
+	NodeType
+	Pos
+	tr   *Tree
+	Text string // Comment text.
+}
+
+func (t *Tree) newComment(pos Pos, text string) *CommentNode {
+	return &CommentNode{tr: t, NodeType: NodeComment, Pos: pos, Text: text}
+}
+
+func (c *CommentNode) String() string {
+	var sb strings.Builder
+	c.writeTo(&sb)
+	return sb.String()
+}
+
+func (c *CommentNode) writeTo(sb *strings.Builder) {
+	sb.WriteString("{{")
+	sb.WriteString(c.Text)
+	sb.WriteString("}}")
+}
+
+func (c *CommentNode) tree() *Tree {
+	return c.tr
+}
+
+func (c *CommentNode) Copy() Node {
+	return &CommentNode{tr: c.tr, NodeType: NodeComment, Pos: c.Pos, Text: c.Text}
+}
+
 // PipeNode holds a pipeline with optional declaration
 type PipeNode struct {
 	NodeType
@@ -349,7 +382,7 @@ func (i *IdentifierNode) Copy() Node {
 	return NewIdentifier(i.Ident).SetTree(i.tr).SetPos(i.Pos)
 }
 
-// AssignNode holds a list of variable names, possibly with chained field
+// VariableNode holds a list of variable names, possibly with chained field
 // accesses. The dollar sign is part of the (first) name.
 type VariableNode struct {
 	NodeType

tpl/internal/go_templates/texttemplate/parse/parse.go

@@ -21,16 +21,26 @@ type Tree struct {
 	Name      string    // name of the template represented by the tree.
 	ParseName string    // name of the top-level template during parsing, for error messages.
 	Root      *ListNode // top-level root of the tree.
+	Mode      Mode      // parsing mode.
 	text      string    // text parsed to create the template (or its parent)
 	// Parsing only; cleared after parse.
-	funcs     []map[string]interface{}
+	funcs      []map[string]interface{}
-	lex       *lexer
+	lex        *lexer
-	token     [3]item // three-token lookahead for parser.
+	token      [3]item // three-token lookahead for parser.
-	peekCount int
+	peekCount  int
-	vars      []string // variables defined at the moment.
+	vars       []string // variables defined at the moment.
-	treeSet   map[string]*Tree
+	treeSet    map[string]*Tree
+	actionLine int // line of left delim starting action
+	mode       Mode
 }
 
+// A mode value is a set of flags (or 0). Modes control parser behavior.
+type Mode uint
+
+const (
+	ParseComments Mode = 1 << iota // parse comments and add them to AST
+)
+
 // Copy returns a copy of the Tree. Any parsing state is discarded.
 func (t *Tree) Copy() *Tree {
 	if t == nil {
@@ -178,6 +188,16 @@ func (t *Tree) expectOneOf(expected1, expected2 itemType, context string) item {
 
 // unexpected complains about the token and terminates processing.
 func (t *Tree) unexpected(token item, context string) {
+	if token.typ == itemError {
+		extra := ""
+		if t.actionLine != 0 && t.actionLine != token.line {
+			extra = fmt.Sprintf(" in action started at %s:%d", t.ParseName, t.actionLine)
+			if strings.HasSuffix(token.val, " action") {
+				extra = extra[len(" in action"):] // avoid "action in action"
+			}
+		}
+		t.errorf("%s%s", token, extra)
+	}
 	t.errorf("unexpected %s in %s", token, context)
 }
 
@@ -220,7 +240,8 @@ func (t *Tree) stopParse() {
 func (t *Tree) Parse(text, leftDelim, rightDelim string, treeSet map[string]*Tree, funcs ...map[string]interface{}) (tree *Tree, err error) {
 	defer t.recover(&err)
 	t.ParseName = t.Name
-	t.startParse(funcs, lex(t.Name, text, leftDelim, rightDelim), treeSet)
+	emitComment := t.Mode&ParseComments != 0
+	t.startParse(funcs, lex(t.Name, text, leftDelim, rightDelim, emitComment), treeSet)
 	t.text = text
 	t.parse()
 	t.add()
@@ -240,12 +261,14 @@ func (t *Tree) add() {
 	}
 }
 
-// IsEmptyTree reports whether this tree (node) is empty of everything but space.
+// IsEmptyTree reports whether this tree (node) is empty of everything but space or comments.
 func IsEmptyTree(n Node) bool {
 	switch n := n.(type) {
 	case nil:
 		return true
 	case *ActionNode:
+	case *CommentNode:
+		return true
 	case *IfNode:
 	case *ListNode:
 		for _, node := range n.Nodes {
@@ -276,6 +299,7 @@ func (t *Tree) parse() {
 			if t.nextNonSpace().typ == itemDefine {
 				newT := New("definition") // name will be updated once we know it.
 				newT.text = t.text
+				newT.Mode = t.Mode
 				newT.ParseName = t.ParseName
 				newT.startParse(t.funcs, t.lex, t.treeSet)
 				newT.parseDefinition()
@@ -331,19 +355,27 @@ func (t *Tree) itemList() (list *ListNode, next Node) {
 }
 
 // textOrAction:
-//	text | action
+//	text | comment | action
 func (t *Tree) textOrAction() Node {
 	switch token := t.nextNonSpace(); token.typ {
 	case itemText:
 		return t.newText(token.pos, token.val)
 	case itemLeftDelim:
+		t.actionLine = token.line
+		defer t.clearActionLine()
 		return t.action()
+	case itemComment:
+		return t.newComment(token.pos, token.val)
 	default:
 		t.unexpected(token, "input")
 	}
 	return nil
 }
 
+func (t *Tree) clearActionLine() {
+	t.actionLine = 0
+}
+
 // Action:
 //	control
 //	command ("|" command)*
@@ -369,12 +401,12 @@ func (t *Tree) action() (n Node) {
 	t.backup()
 	token := t.peek()
 	// Do not pop variables; they persist until "end".
-	return t.newAction(token.pos, token.line, t.pipeline("command"))
+	return t.newAction(token.pos, token.line, t.pipeline("command", itemRightDelim))
 }
 
 // Pipeline:
 //	declarations? command ('|' command)*
-func (t *Tree) pipeline(context string) (pipe *PipeNode) {
+func (t *Tree) pipeline(context string, end itemType) (pipe *PipeNode) {
 	token := t.peekNonSpace()
 	pipe = t.newPipeline(token.pos, token.line, nil)
 	// Are there declarations or assignments?
@@ -415,12 +447,9 @@ decls:
 	}
 	for {
 		switch token := t.nextNonSpace(); token.typ {
-		case itemRightDelim, itemRightParen:
+		case end:
 			// At this point, the pipeline is complete
 			t.checkPipeline(pipe, context)
-			if token.typ == itemRightParen {
-				t.backup()
-			}
 			return
 		case itemBool, itemCharConstant, itemComplex, itemDot, itemField, itemIdentifier,
 			itemNumber, itemNil, itemRawString, itemString, itemVariable, itemLeftParen:
@@ -449,7 +478,7 @@ func (t *Tree) checkPipeline(pipe *PipeNode, context string) {
 
 func (t *Tree) parseControl(allowElseIf bool, context string) (pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) {
 	defer t.popVars(len(t.vars))
-	pipe = t.pipeline(context)
+	pipe = t.pipeline(context, itemRightDelim)
 	var next Node
 	list, next = t.itemList()
 	switch next.Type() {
@@ -535,10 +564,11 @@ func (t *Tree) blockControl() Node {
 
 	token := t.nextNonSpace()
 	name := t.parseTemplateName(token, context)
-	pipe := t.pipeline(context)
+	pipe := t.pipeline(context, itemRightDelim)
 
 	block := New(name) // name will be updated once we know it.
 	block.text = t.text
+	block.Mode = t.Mode
 	block.ParseName = t.ParseName
 	block.startParse(t.funcs, t.lex, t.treeSet)
 	var end Node
@@ -564,7 +594,7 @@ func (t *Tree) templateControl() Node {
 	if t.nextNonSpace().typ != itemRightDelim {
 		t.backup()
 		// Do not pop variables; they persist until "end".
-		pipe = t.pipeline(context)
+		pipe = t.pipeline(context, itemRightDelim)
 	}
 	return t.newTemplate(token.pos, token.line, name, pipe)
 }
@@ -598,13 +628,12 @@ func (t *Tree) command() *CommandNode {
 		switch token := t.next(); token.typ {
 		case itemSpace:
 			continue
-		case itemError:
-			t.errorf("%s", token.val)
 		case itemRightDelim, itemRightParen:
 			t.backup()
 		case itemPipe:
+			// nothing here; break loop below
 		default:
-			t.errorf("unexpected %s in operand", token)
+			t.unexpected(token, "operand")
 		}
 		break
 	}
@@ -659,8 +688,6 @@ func (t *Tree) operand() Node {
 // A nil return means the next item is not a term.
 func (t *Tree) term() Node {
 	switch token := t.nextNonSpace(); token.typ {
-	case itemError:
-		t.errorf("%s", token.val)
 	case itemIdentifier:
 		if !t.hasFunction(token.val) {
 			t.errorf("function %q not defined", token.val)
@@ -683,11 +710,7 @@ func (t *Tree) term() Node {
 		}
 		return number
 	case itemLeftParen:
-		pipe := t.pipeline("parenthesized pipeline")
+		return t.pipeline("parenthesized pipeline", itemRightParen)
-		if token := t.next(); token.typ != itemRightParen {
-			t.errorf("unclosed right paren: unexpected %s", token)
-		}
-		return pipe
 	case itemString, itemRawString:
 		s, err := strconv.Unquote(token.val)
 		if err != nil {

tpl/internal/go_templates/texttemplate/parse/parse_test.go

@@ -252,6 +252,13 @@ var parseTests = []parseTest{
 	{"comment trim left and right", "x \r\n\t{{- /* */ -}}\n\n\ty", noError, `"x""y"`},
 	{"block definition", `{{block "foo" .}}hello{{end}}`, noError,
 		`{{template "foo" .}}`},
+
+	{"newline in assignment", "{{ $x \n := \n 1 \n }}", noError, "{{$x := 1}}"},
+	{"newline in empty action", "{{\n}}", hasError, "{{\n}}"},
+	{"newline in pipeline", "{{\n\"x\"\n|\nprintf\n}}", noError, `{{"x" | printf}}`},
+	{"newline in comment", "{{/*\nhello\n*/}}", noError, ""},
+	{"newline in comment", "{{-\n/*\nhello\n*/\n-}}", noError, ""},
+
 	// Errors.
 	{"unclosed action", "hello{{range", hasError, ""},
 	{"unmatched end", "{{end}}", hasError, ""},
@@ -350,6 +357,30 @@ func TestParseCopy(t *testing.T) {
 	testParse(true, t)
 }
 
+func TestParseWithComments(t *testing.T) {
+	textFormat = "%q"
+	defer func() { textFormat = "%s" }()
+	tests := [...]parseTest{
+		{"comment", "{{/*\n\n\n*/}}", noError, "{{/*\n\n\n*/}}"},
+		{"comment trim left", "x \r\n\t{{- /* hi */}}", noError, `"x"{{/* hi */}}`},
+		{"comment trim right", "{{/* hi */ -}}\n\n\ty", noError, `{{/* hi */}}"y"`},
+		{"comment trim left and right", "x \r\n\t{{- /* */ -}}\n\n\ty", noError, `"x"{{/* */}}"y"`},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			tr := New(test.name)
+			tr.Mode = ParseComments
+			tmpl, err := tr.Parse(test.input, "", "", make(map[string]*Tree))
+			if err != nil {
+				t.Errorf("%q: expected error; got none", test.name)
+			}
+			if result := tmpl.Root.String(); result != test.result {
+				t.Errorf("%s=(%q): got\n\t%v\nexpected\n\t%v", test.name, test.input, result, test.result)
+			}
+		})
+	}
+}
+
 type isEmptyTest struct {
 	name  string
 	input string
@@ -360,6 +391,7 @@ var isEmptyTests = []isEmptyTest{
 	{"empty", ``, true},
 	{"nonempty", `hello`, false},
 	{"spaces only", " \t\n \t\n", true},
+	{"comment only", "{{/* comment */}}", true},
 	{"definition", `{{define "x"}}something{{end}}`, true},
 	{"definitions and space", "{{define `x`}}something{{end}}\n\n{{define `y`}}something{{end}}\n\n", true},
 	{"definitions and text", "{{define `x`}}something{{end}}\nx\n{{define `y`}}something{{end}}\ny\n", false},
@@ -403,23 +435,38 @@ var errorTests = []parseTest{
 	// Check line numbers are accurate.
 	{"unclosed1",
 		"line1\n{{",
-		hasError, `unclosed1:2: unexpected unclosed action in command`},
+		hasError, `unclosed1:2: unclosed action`},
 	{"unclosed2",
 		"line1\n{{define `x`}}line2\n{{",
-		hasError, `unclosed2:3: unexpected unclosed action in command`},
+		hasError, `unclosed2:3: unclosed action`},
+	{"unclosed3",
+		"line1\n{{\"x\"\n\"y\"\n",
+		hasError, `unclosed3:4: unclosed action started at unclosed3:2`},
+	{"unclosed4",
+		"{{\n\n\n\n\n",
+		hasError, `unclosed4:6: unclosed action started at unclosed4:1`},
+	{"var1",
+		"line1\n{{\nx\n}}",
+		hasError, `var1:3: function "x" not defined`},
 	// Specific errors.
 	{"function",
 		"{{foo}}",
 		hasError, `function "foo" not defined`},
-	{"comment",
+	{"comment1",
 		"{{/*}}",
-		hasError, `unclosed comment`},
+		hasError, `comment1:1: unclosed comment`},
+	{"comment2",
+		"{{/*\nhello\n}}",
+		hasError, `comment2:1: unclosed comment`},
 	{"lparen",
 		"{{.X (1 2 3}}",
 		hasError, `unclosed left paren`},
 	{"rparen",
-		"{{.X 1 2 3)}}",
+		"{{.X 1 2 3 ) }}",
-		hasError, `unexpected ")"`},
+		hasError, `unexpected ")" in command`},
+	{"rparen2",
+		"{{(.X 1 2 3",
+		hasError, `unclosed action`},
 	{"space",
 		"{{`x`3}}",
 		hasError, `in operand`},
@@ -465,7 +512,7 @@ var errorTests = []parseTest{
 		hasError, `missing value for parenthesized pipeline`},
 	{"multilinerawstring",
 		"{{ $v := `\n` }} {{",
-		hasError, `multilinerawstring:2: unexpected unclosed action`},
+		hasError, `multilinerawstring:2: unclosed action`},
 	{"rangeundefvar",
 		"{{range $k}}{{end}}",
 		hasError, `undefined variable`},