From 73df946d56c74384511a194dd01dbe099584fd1a Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 28 Apr 2024 15:14:23 +0200
Subject: Adding upstream version 1.16.10.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 src/html/template/escape.go | 892 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 892 insertions(+)
 create mode 100644 src/html/template/escape.go

(limited to 'src/html/template/escape.go')

diff --git a/src/html/template/escape.go b/src/html/template/escape.go
new file mode 100644
index 0000000..8739735
--- /dev/null
+++ b/src/html/template/escape.go
@@ -0,0 +1,892 @@
+// 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.
+
+package template
+
+import (
+	"bytes"
+	"fmt"
+	"html"
+	"io"
+	"text/template"
+	"text/template/parse"
+)
+
+// escapeTemplate rewrites the named template, which must be
+// associated with t, to guarantee that the output of any of the named
+// templates is properly escaped. If no error is returned, then the named templates have
+// been modified. Otherwise the named templates have been rendered
+// unusable.
+func escapeTemplate(tmpl *Template, node parse.Node, name string) error {
+	c, _ := tmpl.esc.escapeTree(context{}, node, name, 0)
+	var err error
+	if c.err != nil {
+		err, c.err.Name = c.err, name
+	} else if c.state != stateText {
+		err = &Error{ErrEndContext, nil, name, 0, fmt.Sprintf("ends in a non-text context: %v", c)}
+	}
+	if err != nil {
+		// Prevent execution of unsafe templates.
+		if t := tmpl.set[name]; t != nil {
+			t.escapeErr = err
+			t.text.Tree = nil
+			t.Tree = nil
+		}
+		return err
+	}
+	tmpl.esc.commit()
+	if t := tmpl.set[name]; t != nil {
+		t.escapeErr = escapeOK
+		t.Tree = t.text.Tree
+	}
+	return nil
+}
+
+// evalArgs formats the list of arguments into a string. It is equivalent to
+// fmt.Sprint(args...), except that it deferences all pointers.
+func evalArgs(args ...interface{}) string {
+	// Optimization for simple common case of a single string argument.
+	if len(args) == 1 {
+		if s, ok := args[0].(string); ok {
+			return s
+		}
+	}
+	for i, arg := range args {
+		args[i] = indirectToStringerOrError(arg)
+	}
+	return fmt.Sprint(args...)
+}
+
+// funcMap maps command names to functions that render their inputs safe.
+var funcMap = template.FuncMap{
+	"_html_template_attrescaper":     attrEscaper,
+	"_html_template_commentescaper":  commentEscaper,
+	"_html_template_cssescaper":      cssEscaper,
+	"_html_template_cssvaluefilter":  cssValueFilter,
+	"_html_template_htmlnamefilter":  htmlNameFilter,
+	"_html_template_htmlescaper":     htmlEscaper,
+	"_html_template_jsregexpescaper": jsRegexpEscaper,
+	"_html_template_jsstrescaper":    jsStrEscaper,
+	"_html_template_jsvalescaper":    jsValEscaper,
+	"_html_template_nospaceescaper":  htmlNospaceEscaper,
+	"_html_template_rcdataescaper":   rcdataEscaper,
+	"_html_template_srcsetescaper":   srcsetFilterAndEscaper,
+	"_html_template_urlescaper":      urlEscaper,
+	"_html_template_urlfilter":       urlFilter,
+	"_html_template_urlnormalizer":   urlNormalizer,
+	"_eval_args_":                    evalArgs,
+}
+
+// escaper collects type inferences about templates and changes needed to make
+// templates injection safe.
+type escaper struct {
+	// ns is the nameSpace that this escaper is associated with.
+	ns *nameSpace
+	// output[templateName] is the output context for a templateName that
+	// has been mangled to include its input context.
+	output map[string]context
+	// derived[c.mangle(name)] maps to a template derived from the template
+	// named name templateName for the start context c.
+	derived map[string]*template.Template
+	// called[templateName] is a set of called mangled template names.
+	called map[string]bool
+	// xxxNodeEdits are the accumulated edits to apply during commit.
+	// Such edits are not applied immediately in case a template set
+	// executes a given template in different escaping contexts.
+	actionNodeEdits   map[*parse.ActionNode][]string
+	templateNodeEdits map[*parse.TemplateNode]string
+	textNodeEdits     map[*parse.TextNode][]byte
+}
+
+// makeEscaper creates a blank escaper for the given set.
+func makeEscaper(n *nameSpace) escaper {
+	return escaper{
+		n,
+		map[string]context{},
+		map[string]*template.Template{},
+		map[string]bool{},
+		map[*parse.ActionNode][]string{},
+		map[*parse.TemplateNode]string{},
+		map[*parse.TextNode][]byte{},
+	}
+}
+
+// filterFailsafe is an innocuous word that is emitted in place of unsafe values
+// by sanitizer functions. It is not a keyword in any programming language,
+// contains no special characters, is not empty, and when it appears in output
+// it is distinct enough that a developer can find the source of the problem
+// via a search engine.
+const filterFailsafe = "ZgotmplZ"
+
+// escape escapes a template node.
+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:
+		return e.escapeList(c, n)
+	case *parse.RangeNode:
+		return e.escapeBranch(c, &n.BranchNode, "range")
+	case *parse.TemplateNode:
+		return e.escapeTemplate(c, n)
+	case *parse.TextNode:
+		return e.escapeText(c, n)
+	case *parse.WithNode:
+		return e.escapeBranch(c, &n.BranchNode, "with")
+	}
+	panic("escaping " + n.String() + " is unimplemented")
+}
+
+// escapeAction escapes an action template node.
+func (e *escaper) escapeAction(c context, n *parse.ActionNode) context {
+	if len(n.Pipe.Decl) != 0 {
+		// A local variable assignment, not an interpolation.
+		return c
+	}
+	c = nudge(c)
+	// Check for disallowed use of predefined escapers in the pipeline.
+	for pos, idNode := range n.Pipe.Cmds {
+		node, ok := idNode.Args[0].(*parse.IdentifierNode)
+		if !ok {
+			// A predefined escaper "esc" will never be found as an identifier in a
+			// Chain or Field node, since:
+			// - "esc.x ..." is invalid, since predefined escapers return strings, and
+			//   strings do not have methods, keys or fields.
+			// - "... .esc" is invalid, since predefined escapers are global functions,
+			//   not methods or fields of any types.
+			// Therefore, it is safe to ignore these two node types.
+			continue
+		}
+		ident := node.Ident
+		if _, ok := predefinedEscapers[ident]; ok {
+			if pos < len(n.Pipe.Cmds)-1 ||
+				c.state == stateAttr && c.delim == delimSpaceOrTagEnd && ident == "html" {
+				return context{
+					state: stateError,
+					err:   errorf(ErrPredefinedEscaper, n, n.Line, "predefined escaper %q disallowed in template", ident),
+				}
+			}
+		}
+	}
+	s := make([]string, 0, 3)
+	switch c.state {
+	case stateError:
+		return c
+	case stateURL, stateCSSDqStr, stateCSSSqStr, stateCSSDqURL, stateCSSSqURL, stateCSSURL:
+		switch c.urlPart {
+		case urlPartNone:
+			s = append(s, "_html_template_urlfilter")
+			fallthrough
+		case urlPartPreQuery:
+			switch c.state {
+			case stateCSSDqStr, stateCSSSqStr:
+				s = append(s, "_html_template_cssescaper")
+			default:
+				s = append(s, "_html_template_urlnormalizer")
+			}
+		case urlPartQueryOrFrag:
+			s = append(s, "_html_template_urlescaper")
+		case urlPartUnknown:
+			return context{
+				state: stateError,
+				err:   errorf(ErrAmbigContext, n, n.Line, "%s appears in an ambiguous context within a URL", n),
+			}
+		default:
+			panic(c.urlPart.String())
+		}
+	case stateJS:
+		s = append(s, "_html_template_jsvalescaper")
+		// A slash after a value starts a div operator.
+		c.jsCtx = jsCtxDivOp
+	case stateJSDqStr, stateJSSqStr:
+		s = append(s, "_html_template_jsstrescaper")
+	case stateJSRegexp:
+		s = append(s, "_html_template_jsregexpescaper")
+	case stateCSS:
+		s = append(s, "_html_template_cssvaluefilter")
+	case stateText:
+		s = append(s, "_html_template_htmlescaper")
+	case stateRCDATA:
+		s = append(s, "_html_template_rcdataescaper")
+	case stateAttr:
+		// Handled below in delim check.
+	case stateAttrName, stateTag:
+		c.state = stateAttrName
+		s = append(s, "_html_template_htmlnamefilter")
+	case stateSrcset:
+		s = append(s, "_html_template_srcsetescaper")
+	default:
+		if isComment(c.state) {
+			s = append(s, "_html_template_commentescaper")
+		} else {
+			panic("unexpected state " + c.state.String())
+		}
+	}
+	switch c.delim {
+	case delimNone:
+		// No extra-escaping needed for raw text content.
+	case delimSpaceOrTagEnd:
+		s = append(s, "_html_template_nospaceescaper")
+	default:
+		s = append(s, "_html_template_attrescaper")
+	}
+	e.editActionNode(n, s)
+	return c
+}
+
+// ensurePipelineContains ensures that the pipeline ends with the commands with
+// the identifiers in s in order. If the pipeline ends with a predefined escaper
+// (i.e. "html" or "urlquery"), merge it with the identifiers in s.
+func ensurePipelineContains(p *parse.PipeNode, s []string) {
+	if len(s) == 0 {
+		// Do not rewrite pipeline if we have no escapers to insert.
+		return
+	}
+	// Precondition: p.Cmds contains at most one predefined escaper and the
+	// escaper will be present at p.Cmds[len(p.Cmds)-1]. This precondition is
+	// always true because of the checks in escapeAction.
+	pipelineLen := len(p.Cmds)
+	if pipelineLen > 0 {
+		lastCmd := p.Cmds[pipelineLen-1]
+		if idNode, ok := lastCmd.Args[0].(*parse.IdentifierNode); ok {
+			if esc := idNode.Ident; predefinedEscapers[esc] {
+				// Pipeline ends with a predefined escaper.
+				if len(p.Cmds) == 1 && len(lastCmd.Args) > 1 {
+					// Special case: pipeline is of the form {{ esc arg1 arg2 ... argN }},
+					// where esc is the predefined escaper, and arg1...argN are its arguments.
+					// Convert this into the equivalent form
+					// {{ _eval_args_ arg1 arg2 ... argN | esc }}, so that esc can be easily
+					// merged with the escapers in s.
+					lastCmd.Args[0] = parse.NewIdentifier("_eval_args_").SetTree(nil).SetPos(lastCmd.Args[0].Position())
+					p.Cmds = appendCmd(p.Cmds, newIdentCmd(esc, p.Position()))
+					pipelineLen++
+				}
+				// If any of the commands in s that we are about to insert is equivalent
+				// to the predefined escaper, use the predefined escaper instead.
+				dup := false
+				for i, escaper := range s {
+					if escFnsEq(esc, escaper) {
+						s[i] = idNode.Ident
+						dup = true
+					}
+				}
+				if dup {
+					// The predefined escaper will already be inserted along with the
+					// escapers in s, so do not copy it to the rewritten pipeline.
+					pipelineLen--
+				}
+			}
+		}
+	}
+	// Rewrite the pipeline, creating the escapers in s at the end of the pipeline.
+	newCmds := make([]*parse.CommandNode, pipelineLen, pipelineLen+len(s))
+	insertedIdents := make(map[string]bool)
+	for i := 0; i < pipelineLen; i++ {
+		cmd := p.Cmds[i]
+		newCmds[i] = cmd
+		if idNode, ok := cmd.Args[0].(*parse.IdentifierNode); ok {
+			insertedIdents[normalizeEscFn(idNode.Ident)] = true
+		}
+	}
+	for _, name := range s {
+		if !insertedIdents[normalizeEscFn(name)] {
+			// When two templates share an underlying parse tree via the use of
+			// AddParseTree and one template is executed after the other, this check
+			// ensures that escapers that were already inserted into the pipeline on
+			// the first escaping pass do not get inserted again.
+			newCmds = appendCmd(newCmds, newIdentCmd(name, p.Position()))
+		}
+	}
+	p.Cmds = newCmds
+}
+
+// predefinedEscapers contains template predefined escapers that are equivalent
+// to some contextual escapers. Keep in sync with equivEscapers.
+var predefinedEscapers = map[string]bool{
+	"html":     true,
+	"urlquery": true,
+}
+
+// equivEscapers matches contextual escapers to equivalent predefined
+// template escapers.
+var equivEscapers = map[string]string{
+	// The following pairs of HTML escapers provide equivalent security
+	// guarantees, since they all escape '\000', '\'', '"', '&', '<', and '>'.
+	"_html_template_attrescaper":   "html",
+	"_html_template_htmlescaper":   "html",
+	"_html_template_rcdataescaper": "html",
+	// These two URL escapers produce URLs safe for embedding in a URL query by
+	// percent-encoding all the reserved characters specified in RFC 3986 Section
+	// 2.2
+	"_html_template_urlescaper": "urlquery",
+	// These two functions are not actually equivalent; urlquery is stricter as it
+	// escapes reserved characters (e.g. '#'), while _html_template_urlnormalizer
+	// does not. It is therefore only safe to replace _html_template_urlnormalizer
+	// with urlquery (this happens in ensurePipelineContains), but not the otherI've
+	// way around. We keep this entry around to preserve the behavior of templates
+	// written before Go 1.9, which might depend on this substitution taking place.
+	"_html_template_urlnormalizer": "urlquery",
+}
+
+// escFnsEq reports whether the two escaping functions are equivalent.
+func escFnsEq(a, b string) bool {
+	return normalizeEscFn(a) == normalizeEscFn(b)
+}
+
+// normalizeEscFn(a) is equal to normalizeEscFn(b) for any pair of names of
+// escaper functions a and b that are equivalent.
+func normalizeEscFn(e string) string {
+	if norm := equivEscapers[e]; norm != "" {
+		return norm
+	}
+	return e
+}
+
+// redundantFuncs[a][b] implies that funcMap[b](funcMap[a](x)) == funcMap[a](x)
+// for all x.
+var redundantFuncs = map[string]map[string]bool{
+	"_html_template_commentescaper": {
+		"_html_template_attrescaper":    true,
+		"_html_template_nospaceescaper": true,
+		"_html_template_htmlescaper":    true,
+	},
+	"_html_template_cssescaper": {
+		"_html_template_attrescaper": true,
+	},
+	"_html_template_jsregexpescaper": {
+		"_html_template_attrescaper": true,
+	},
+	"_html_template_jsstrescaper": {
+		"_html_template_attrescaper": true,
+	},
+	"_html_template_urlescaper": {
+		"_html_template_urlnormalizer": true,
+	},
+}
+
+// appendCmd appends the given command to the end of the command pipeline
+// unless it is redundant with the last command.
+func appendCmd(cmds []*parse.CommandNode, cmd *parse.CommandNode) []*parse.CommandNode {
+	if n := len(cmds); n != 0 {
+		last, okLast := cmds[n-1].Args[0].(*parse.IdentifierNode)
+		next, okNext := cmd.Args[0].(*parse.IdentifierNode)
+		if okLast && okNext && redundantFuncs[last.Ident][next.Ident] {
+			return cmds
+		}
+	}
+	return append(cmds, cmd)
+}
+
+// newIdentCmd produces a command containing a single identifier node.
+func newIdentCmd(identifier string, pos parse.Pos) *parse.CommandNode {
+	return &parse.CommandNode{
+		NodeType: parse.NodeCommand,
+		Args:     []parse.Node{parse.NewIdentifier(identifier).SetTree(nil).SetPos(pos)}, // TODO: SetTree.
+	}
+}
+
+// nudge returns the context that would result from following empty string
+// transitions from the input context.
+// For example, parsing:
+//     `<a href=`
+// will end in context{stateBeforeValue, attrURL}, but parsing one extra rune:
+//     `<a href=x`
+// will end in context{stateURL, delimSpaceOrTagEnd, ...}.
+// There are two transitions that happen when the 'x' is seen:
+// (1) Transition from a before-value state to a start-of-value state without
+//     consuming any character.
+// (2) Consume 'x' and transition past the first value character.
+// In this case, nudging produces the context after (1) happens.
+func nudge(c context) context {
+	switch c.state {
+	case stateTag:
+		// In `<foo {{.}}`, the action should emit an attribute.
+		c.state = stateAttrName
+	case stateBeforeValue:
+		// In `<foo bar={{.}}`, the action is an undelimited value.
+		c.state, c.delim, c.attr = attrStartStates[c.attr], delimSpaceOrTagEnd, attrNone
+	case stateAfterName:
+		// In `<foo bar {{.}}`, the action is an attribute name.
+		c.state, c.attr = stateAttrName, attrNone
+	}
+	return c
+}
+
+// join joins the two contexts of a branch template node. The result is an
+// error context if either of the input contexts are error contexts, or if the
+// input contexts differ.
+func join(a, b context, node parse.Node, nodeName string) context {
+	if a.state == stateError {
+		return a
+	}
+	if b.state == stateError {
+		return b
+	}
+	if a.eq(b) {
+		return a
+	}
+
+	c := a
+	c.urlPart = b.urlPart
+	if c.eq(b) {
+		// The contexts differ only by urlPart.
+		c.urlPart = urlPartUnknown
+		return c
+	}
+
+	c = a
+	c.jsCtx = b.jsCtx
+	if c.eq(b) {
+		// The contexts differ only by jsCtx.
+		c.jsCtx = jsCtxUnknown
+		return c
+	}
+
+	// Allow a nudged context to join with an unnudged one.
+	// This means that
+	//   <p title={{if .C}}{{.}}{{end}}
+	// ends in an unquoted value state even though the else branch
+	// ends in stateBeforeValue.
+	if c, d := nudge(a), nudge(b); !(c.eq(a) && d.eq(b)) {
+		if e := join(c, d, node, nodeName); e.state != stateError {
+			return e
+		}
+	}
+
+	return context{
+		state: stateError,
+		err:   errorf(ErrBranchEnd, node, 0, "{{%s}} branches end in different contexts: %v, %v", nodeName, a, b),
+	}
+}
+
+// escapeBranch escapes a branch template node: "if", "range" and "with".
+func (e *escaper) escapeBranch(c context, n *parse.BranchNode, nodeName string) context {
+	c0 := e.escapeList(c, n.List)
+	if nodeName == "range" && c0.state != stateError {
+		// The "true" branch of a "range" node can execute multiple times.
+		// We check that executing n.List once results in the same context
+		// as executing n.List twice.
+		c1, _ := e.escapeListConditionally(c0, n.List, nil)
+		c0 = join(c0, c1, n, nodeName)
+		if c0.state == stateError {
+			// Make clear that this is a problem on loop re-entry
+			// since developers tend to overlook that branch when
+			// debugging templates.
+			c0.err.Line = n.Line
+			c0.err.Description = "on range loop re-entry: " + c0.err.Description
+			return c0
+		}
+	}
+	c1 := e.escapeList(c, n.ElseList)
+	return join(c0, c1, n, nodeName)
+}
+
+// escapeList escapes a list template node.
+func (e *escaper) escapeList(c context, n *parse.ListNode) context {
+	if n == nil {
+		return c
+	}
+	for _, m := range n.Nodes {
+		c = e.escape(c, m)
+	}
+	return c
+}
+
+// escapeListConditionally escapes a list node but only preserves edits and
+// inferences in e if the inferences and output context satisfy filter.
+// It returns the best guess at an output context, and the result of the filter
+// which is the same as whether e was updated.
+func (e *escaper) escapeListConditionally(c context, n *parse.ListNode, filter func(*escaper, context) bool) (context, bool) {
+	e1 := makeEscaper(e.ns)
+	// Make type inferences available to f.
+	for k, v := range e.output {
+		e1.output[k] = v
+	}
+	c = e1.escapeList(c, n)
+	ok := filter != nil && filter(&e1, c)
+	if ok {
+		// Copy inferences and edits from e1 back into e.
+		for k, v := range e1.output {
+			e.output[k] = v
+		}
+		for k, v := range e1.derived {
+			e.derived[k] = v
+		}
+		for k, v := range e1.called {
+			e.called[k] = v
+		}
+		for k, v := range e1.actionNodeEdits {
+			e.editActionNode(k, v)
+		}
+		for k, v := range e1.templateNodeEdits {
+			e.editTemplateNode(k, v)
+		}
+		for k, v := range e1.textNodeEdits {
+			e.editTextNode(k, v)
+		}
+	}
+	return c, ok
+}
+
+// escapeTemplate escapes a {{template}} call node.
+func (e *escaper) escapeTemplate(c context, n *parse.TemplateNode) context {
+	c, name := e.escapeTree(c, n, n.Name, n.Line)
+	if name != n.Name {
+		e.editTemplateNode(n, name)
+	}
+	return c
+}
+
+// escapeTree escapes the named template starting in the given context as
+// necessary and returns its output context.
+func (e *escaper) escapeTree(c context, node parse.Node, name string, line int) (context, string) {
+	// Mangle the template name with the input context to produce a reliable
+	// identifier.
+	dname := c.mangle(name)
+	e.called[dname] = true
+	if out, ok := e.output[dname]; ok {
+		// Already escaped.
+		return out, dname
+	}
+	t := e.template(name)
+	if t == nil {
+		// Two cases: The template exists but is empty, or has never been mentioned at
+		// all. Distinguish the cases in the error messages.
+		if e.ns.set[name] != nil {
+			return context{
+				state: stateError,
+				err:   errorf(ErrNoSuchTemplate, node, line, "%q is an incomplete or empty template", name),
+			}, dname
+		}
+		return context{
+			state: stateError,
+			err:   errorf(ErrNoSuchTemplate, node, line, "no such template %q", name),
+		}, dname
+	}
+	if dname != name {
+		// Use any template derived during an earlier call to escapeTemplate
+		// with different top level templates, or clone if necessary.
+		dt := e.template(dname)
+		if dt == nil {
+			dt = template.New(dname)
+			dt.Tree = &parse.Tree{Name: dname, Root: t.Root.CopyList()}
+			e.derived[dname] = dt
+		}
+		t = dt
+	}
+	return e.computeOutCtx(c, t), dname
+}
+
+// computeOutCtx takes a template and its start context and computes the output
+// context while storing any inferences in e.
+func (e *escaper) computeOutCtx(c context, t *template.Template) context {
+	// Propagate context over the body.
+	c1, ok := e.escapeTemplateBody(c, t)
+	if !ok {
+		// Look for a fixed point by assuming c1 as the output context.
+		if c2, ok2 := e.escapeTemplateBody(c1, t); ok2 {
+			c1, ok = c2, true
+		}
+		// Use c1 as the error context if neither assumption worked.
+	}
+	if !ok && c1.state != stateError {
+		return context{
+			state: stateError,
+			err:   errorf(ErrOutputContext, t.Tree.Root, 0, "cannot compute output context for template %s", t.Name()),
+		}
+	}
+	return c1
+}
+
+// escapeTemplateBody escapes the given template assuming the given output
+// context, and returns the best guess at the output context and whether the
+// assumption was correct.
+func (e *escaper) escapeTemplateBody(c context, t *template.Template) (context, bool) {
+	filter := func(e1 *escaper, c1 context) bool {
+		if c1.state == stateError {
+			// Do not update the input escaper, e.
+			return false
+		}
+		if !e1.called[t.Name()] {
+			// If t is not recursively called, then c1 is an
+			// accurate output context.
+			return true
+		}
+		// c1 is accurate if it matches our assumed output context.
+		return c.eq(c1)
+	}
+	// We need to assume an output context so that recursive template calls
+	// take the fast path out of escapeTree instead of infinitely recursing.
+	// Naively assuming that the input context is the same as the output
+	// works >90% of the time.
+	e.output[t.Name()] = c
+	return e.escapeListConditionally(c, t.Tree.Root, filter)
+}
+
+// delimEnds maps each delim to a string of characters that terminate it.
+var delimEnds = [...]string{
+	delimDoubleQuote: `"`,
+	delimSingleQuote: "'",
+	// Determined empirically by running the below in various browsers.
+	// var div = document.createElement("DIV");
+	// for (var i = 0; i < 0x10000; ++i) {
+	//   div.innerHTML = "<span title=x" + String.fromCharCode(i) + "-bar>";
+	//   if (div.getElementsByTagName("SPAN")[0].title.indexOf("bar") < 0)
+	//     document.write("<p>U+" + i.toString(16));
+	// }
+	delimSpaceOrTagEnd: " \t\n\f\r>",
+}
+
+var doctypeBytes = []byte("<!DOCTYPE")
+
+// escapeText escapes a text template node.
+func (e *escaper) escapeText(c context, n *parse.TextNode) context {
+	s, written, i, b := n.Text, 0, 0, new(bytes.Buffer)
+	for i != len(s) {
+		c1, nread := contextAfterText(c, s[i:])
+		i1 := i + nread
+		if c.state == stateText || c.state == stateRCDATA {
+			end := i1
+			if c1.state != c.state {
+				for j := end - 1; j >= i; j-- {
+					if s[j] == '<' {
+						end = j
+						break
+					}
+				}
+			}
+			for j := i; j < end; j++ {
+				if s[j] == '<' && !bytes.HasPrefix(bytes.ToUpper(s[j:]), doctypeBytes) {
+					b.Write(s[written:j])
+					b.WriteString("&lt;")
+					written = j + 1
+				}
+			}
+		} else if isComment(c.state) && c.delim == delimNone {
+			switch c.state {
+			case stateJSBlockCmt:
+				// https://es5.github.com/#x7.4:
+				// "Comments behave like white space and are
+				// discarded except that, if a MultiLineComment
+				// contains a line terminator character, then
+				// the entire comment is considered to be a
+				// LineTerminator for purposes of parsing by
+				// the syntactic grammar."
+				if bytes.ContainsAny(s[written:i1], "\n\r\u2028\u2029") {
+					b.WriteByte('\n')
+				} else {
+					b.WriteByte(' ')
+				}
+			case stateCSSBlockCmt:
+				b.WriteByte(' ')
+			}
+			written = i1
+		}
+		if c.state != c1.state && isComment(c1.state) && c1.delim == delimNone {
+			// Preserve the portion between written and the comment start.
+			cs := i1 - 2
+			if c1.state == stateHTMLCmt {
+				// "<!--" instead of "/*" or "//"
+				cs -= 2
+			}
+			b.Write(s[written:cs])
+			written = i1
+		}
+		if i == i1 && c.state == c1.state {
+			panic(fmt.Sprintf("infinite loop from %v to %v on %q..%q", c, c1, s[:i], s[i:]))
+		}
+		c, i = c1, i1
+	}
+
+	if written != 0 && c.state != stateError {
+		if !isComment(c.state) || c.delim != delimNone {
+			b.Write(n.Text[written:])
+		}
+		e.editTextNode(n, b.Bytes())
+	}
+	return c
+}
+
+// contextAfterText starts in context c, consumes some tokens from the front of
+// s, then returns the context after those tokens and the unprocessed suffix.
+func contextAfterText(c context, s []byte) (context, int) {
+	if c.delim == delimNone {
+		c1, i := tSpecialTagEnd(c, s)
+		if i == 0 {
+			// A special end tag (`</script>`) has been seen and
+			// all content preceding it has been consumed.
+			return c1, 0
+		}
+		// Consider all content up to any end tag.
+		return transitionFunc[c.state](c, s[:i])
+	}
+
+	// We are at the beginning of an attribute value.
+
+	i := bytes.IndexAny(s, delimEnds[c.delim])
+	if i == -1 {
+		i = len(s)
+	}
+	if c.delim == delimSpaceOrTagEnd {
+		// https://www.w3.org/TR/html5/syntax.html#attribute-value-(unquoted)-state
+		// lists the runes below as error characters.
+		// Error out because HTML parsers may differ on whether
+		// "<a id= onclick=f("     ends inside id's or onclick's value,
+		// "<a class=`foo "        ends inside a value,
+		// "<a style=font:'Arial'" needs open-quote fixup.
+		// IE treats '`' as a quotation character.
+		if j := bytes.IndexAny(s[:i], "\"'<=`"); j >= 0 {
+			return context{
+				state: stateError,
+				err:   errorf(ErrBadHTML, nil, 0, "%q in unquoted attr: %q", s[j:j+1], s[:i]),
+			}, len(s)
+		}
+	}
+	if i == len(s) {
+		// Remain inside the attribute.
+		// Decode the value so non-HTML rules can easily handle
+		//     <button onclick="alert(&quot;Hi!&quot;)">
+		// without having to entity decode token boundaries.
+		for u := []byte(html.UnescapeString(string(s))); len(u) != 0; {
+			c1, i1 := transitionFunc[c.state](c, u)
+			c, u = c1, u[i1:]
+		}
+		return c, len(s)
+	}
+
+	element := c.element
+
+	// If this is a non-JS "type" attribute inside "script" tag, do not treat the contents as JS.
+	if c.state == stateAttr && c.element == elementScript && c.attr == attrScriptType && !isJSType(string(s[:i])) {
+		element = elementNone
+	}
+
+	if c.delim != delimSpaceOrTagEnd {
+		// Consume any quote.
+		i++
+	}
+	// On exiting an attribute, we discard all state information
+	// except the state and element.
+	return context{state: stateTag, element: element}, i
+}
+
+// editActionNode records a change to an action pipeline for later commit.
+func (e *escaper) editActionNode(n *parse.ActionNode, cmds []string) {
+	if _, ok := e.actionNodeEdits[n]; ok {
+		panic(fmt.Sprintf("node %s shared between templates", n))
+	}
+	e.actionNodeEdits[n] = cmds
+}
+
+// editTemplateNode records a change to a {{template}} callee for later commit.
+func (e *escaper) editTemplateNode(n *parse.TemplateNode, callee string) {
+	if _, ok := e.templateNodeEdits[n]; ok {
+		panic(fmt.Sprintf("node %s shared between templates", n))
+	}
+	e.templateNodeEdits[n] = callee
+}
+
+// editTextNode records a change to a text node for later commit.
+func (e *escaper) editTextNode(n *parse.TextNode, text []byte) {
+	if _, ok := e.textNodeEdits[n]; ok {
+		panic(fmt.Sprintf("node %s shared between templates", n))
+	}
+	e.textNodeEdits[n] = text
+}
+
+// commit applies changes to actions and template calls needed to contextually
+// autoescape content and adds any derived templates to the set.
+func (e *escaper) commit() {
+	for name := range e.output {
+		e.template(name).Funcs(funcMap)
+	}
+	// Any template from the name space associated with this escaper can be used
+	// to add derived templates to the underlying text/template name space.
+	tmpl := e.arbitraryTemplate()
+	for _, t := range e.derived {
+		if _, err := tmpl.text.AddParseTree(t.Name(), t.Tree); err != nil {
+			panic("error adding derived template")
+		}
+	}
+	for n, s := range e.actionNodeEdits {
+		ensurePipelineContains(n.Pipe, s)
+	}
+	for n, name := range e.templateNodeEdits {
+		n.Name = name
+	}
+	for n, s := range e.textNodeEdits {
+		n.Text = s
+	}
+	// Reset state that is specific to this commit so that the same changes are
+	// not re-applied to the template on subsequent calls to commit.
+	e.called = make(map[string]bool)
+	e.actionNodeEdits = make(map[*parse.ActionNode][]string)
+	e.templateNodeEdits = make(map[*parse.TemplateNode]string)
+	e.textNodeEdits = make(map[*parse.TextNode][]byte)
+}
+
+// template returns the named template given a mangled template name.
+func (e *escaper) template(name string) *template.Template {
+	// Any template from the name space associated with this escaper can be used
+	// to look up templates in the underlying text/template name space.
+	t := e.arbitraryTemplate().text.Lookup(name)
+	if t == nil {
+		t = e.derived[name]
+	}
+	return t
+}
+
+// arbitraryTemplate returns an arbitrary template from the name space
+// associated with e and panics if no templates are found.
+func (e *escaper) arbitraryTemplate() *Template {
+	for _, t := range e.ns.set {
+		return t
+	}
+	panic("no templates in name space")
+}
+
+// Forwarding functions so that clients need only import this package
+// to reach the general escaping functions of text/template.
+
+// HTMLEscape writes to w the escaped HTML equivalent of the plain text data b.
+func HTMLEscape(w io.Writer, b []byte) {
+	template.HTMLEscape(w, b)
+}
+
+// HTMLEscapeString returns the escaped HTML equivalent of the plain text data s.
+func HTMLEscapeString(s string) string {
+	return template.HTMLEscapeString(s)
+}
+
+// HTMLEscaper returns the escaped HTML equivalent of the textual
+// representation of its arguments.
+func HTMLEscaper(args ...interface{}) string {
+	return template.HTMLEscaper(args...)
+}
+
+// JSEscape writes to w the escaped JavaScript equivalent of the plain text data b.
+func JSEscape(w io.Writer, b []byte) {
+	template.JSEscape(w, b)
+}
+
+// JSEscapeString returns the escaped JavaScript equivalent of the plain text data s.
+func JSEscapeString(s string) string {
+	return template.JSEscapeString(s)
+}
+
+// JSEscaper returns the escaped JavaScript equivalent of the textual
+// representation of its arguments.
+func JSEscaper(args ...interface{}) string {
+	return template.JSEscaper(args...)
+}
+
+// URLQueryEscaper returns the escaped value of the textual representation of
+// its arguments in a form suitable for embedding in a URL query.
+func URLQueryEscaper(args ...interface{}) string {
+	return template.URLQueryEscaper(args...)
+}
-- 
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