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// 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 (
// context describes the state an HTML parser must be in when it reaches the
// portion of HTML produced by evaluating a particular template node.
// The zero value of type context is the start context for a template that
// produces an HTML fragment as defined at
// where the context element is null.
type context struct {
state state
delim delim
urlPart urlPart
jsCtx jsCtx
attr attr
element element
err *Error
func (c context) String() string {
var err error
if c.err != nil {
err = c.err
return fmt.Sprintf("{%v %v %v %v %v %v %v}", c.state, c.delim, c.urlPart, c.jsCtx, c.attr, c.element, err)
// eq reports whether two contexts are equal.
func (c context) eq(d context) bool {
return c.state == d.state &&
c.delim == d.delim &&
c.urlPart == d.urlPart &&
c.jsCtx == d.jsCtx &&
c.attr == d.attr &&
c.element == d.element &&
c.err == d.err
// mangle produces an identifier that includes a suffix that distinguishes it
// from template names mangled with different contexts.
func (c context) mangle(templateName string) string {
// The mangled name for the default context is the input templateName.
if c.state == stateText {
return templateName
s := templateName + "$htmltemplate_" + c.state.String()
if c.delim != delimNone {
s += "_" + c.delim.String()
if c.urlPart != urlPartNone {
s += "_" + c.urlPart.String()
if c.jsCtx != jsCtxRegexp {
s += "_" + c.jsCtx.String()
if c.attr != attrNone {
s += "_" + c.attr.String()
if c.element != elementNone {
s += "_" + c.element.String()
return s
// state describes a high-level HTML parser state.
// It bounds the top of the element stack, and by extension the HTML insertion
// mode, but also contains state that does not correspond to anything in the
// HTML5 parsing algorithm because a single token production in the HTML
// grammar may contain embedded actions in a template. For instance, the quoted
// HTML attribute produced by
// <div title="Hello {{.World}}">
// is a single token in HTML's grammar but in a template spans several nodes.
type state uint8
//go:generate stringer -type state
const (
// stateText is parsed character data. An HTML parser is in
// this state when its parse position is outside an HTML tag,
// directive, comment, and special element body.
stateText state = iota
// stateTag occurs before an HTML attribute or the end of a tag.
// stateAttrName occurs inside an attribute name.
// It occurs between the ^'s in ` ^name^ = value`.
// stateAfterName occurs after an attr name has ended but before any
// equals sign. It occurs between the ^'s in ` name^ ^= value`.
// stateBeforeValue occurs after the equals sign but before the value.
// It occurs between the ^'s in ` name =^ ^value`.
// stateHTMLCmt occurs inside an <!-- HTML comment -->.
// stateRCDATA occurs inside an RCDATA element (<textarea> or <title>)
// as described at
// stateAttr occurs inside an HTML attribute whose content is text.
// stateURL occurs inside an HTML attribute whose content is a URL.
// stateSrcset occurs inside an HTML srcset attribute.
// stateJS occurs inside an event handler or script element.
// stateJSDqStr occurs inside a JavaScript double quoted string.
// stateJSSqStr occurs inside a JavaScript single quoted string.
// stateJSRegexp occurs inside a JavaScript regexp literal.
// stateJSBlockCmt occurs inside a JavaScript /* block comment */.
// stateJSLineCmt occurs inside a JavaScript // line comment.
// stateCSS occurs inside a <style> element or style attribute.
// stateCSSDqStr occurs inside a CSS double quoted string.
// stateCSSSqStr occurs inside a CSS single quoted string.
// stateCSSDqURL occurs inside a CSS double quoted url("...").
// stateCSSSqURL occurs inside a CSS single quoted url('...').
// stateCSSURL occurs inside a CSS unquoted url(...).
// stateCSSBlockCmt occurs inside a CSS /* block comment */.
// stateCSSLineCmt occurs inside a CSS // line comment.
// stateError is an infectious error state outside any valid
// HTML/CSS/JS construct.
// isComment is true for any state that contains content meant for template
// authors & maintainers, not for end-users or machines.
func isComment(s state) bool {
switch s {
case stateHTMLCmt, stateJSBlockCmt, stateJSLineCmt, stateCSSBlockCmt, stateCSSLineCmt:
return true
return false
// isInTag return whether s occurs solely inside an HTML tag.
func isInTag(s state) bool {
switch s {
case stateTag, stateAttrName, stateAfterName, stateBeforeValue, stateAttr:
return true
return false
// delim is the delimiter that will end the current HTML attribute.
type delim uint8
//go:generate stringer -type delim
const (
// delimNone occurs outside any attribute.
delimNone delim = iota
// delimDoubleQuote occurs when a double quote (") closes the attribute.
// delimSingleQuote occurs when a single quote (') closes the attribute.
// delimSpaceOrTagEnd occurs when a space or right angle bracket (>)
// closes the attribute.
// urlPart identifies a part in an RFC 3986 hierarchical URL to allow different
// encoding strategies.
type urlPart uint8
//go:generate stringer -type urlPart
const (
// urlPartNone occurs when not in a URL, or possibly at the start:
// ^ in "^http://auth/path?k=v#frag".
urlPartNone urlPart = iota
// urlPartPreQuery occurs in the scheme, authority, or path; between the
// ^s in "h^ttp://auth/path^?k=v#frag".
// urlPartQueryOrFrag occurs in the query portion between the ^s in
// "http://auth/path?^k=v#frag^".
// urlPartUnknown occurs due to joining of contexts both before and
// after the query separator.
// jsCtx determines whether a '/' starts a regular expression literal or a
// division operator.
type jsCtx uint8
//go:generate stringer -type jsCtx
const (
// jsCtxRegexp occurs where a '/' would start a regexp literal.
jsCtxRegexp jsCtx = iota
// jsCtxDivOp occurs where a '/' would start a division operator.
// jsCtxUnknown occurs where a '/' is ambiguous due to context joining.
// element identifies the HTML element when inside a start tag or special body.
// Certain HTML element (for example <script> and <style>) have bodies that are
// treated differently from stateText so the element type is necessary to
// transition into the correct context at the end of a tag and to identify the
// end delimiter for the body.
type element uint8
//go:generate stringer -type element
const (
// elementNone occurs outside a special tag or special element body.
elementNone element = iota
// elementScript corresponds to the raw text <script> element
// with JS MIME type or no type attribute.
// elementStyle corresponds to the raw text <style> element.
// elementTextarea corresponds to the RCDATA <textarea> element.
// elementTitle corresponds to the RCDATA <title> element.
//go:generate stringer -type attr
// attr identifies the current HTML attribute when inside the attribute,
// that is, starting from stateAttrName until stateTag/stateText (exclusive).
type attr uint8
const (
// attrNone corresponds to a normal attribute or no attribute.
attrNone attr = iota
// attrScript corresponds to an event handler attribute.
// attrScriptType corresponds to the type attribute in script HTML element
// attrStyle corresponds to the style attribute whose value is CSS.
// attrURL corresponds to an attribute whose value is a URL.
// attrSrcset corresponds to a srcset attribute.