// 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"
"encoding/json"
"fmt"
"reflect"
"strings"
"unicode/utf8"
)
// nextJSCtx returns the context that determines whether a slash after the
// given run of tokens starts a regular expression instead of a division
// operator: / or /=.
//
// This assumes that the token run does not include any string tokens, comment
// tokens, regular expression literal tokens, or division operators.
//
// This fails on some valid but nonsensical JavaScript programs like
// "x = ++/foo/i" which is quite different than "x++/foo/i", but is not known to
// fail on any known useful programs. It is based on the draft
// JavaScript 2.0 lexical grammar and requires one token of lookbehind:
// https://www.mozilla.org/js/language/js20-2000-07/rationale/syntax.html
func nextJSCtx(s []byte, preceding jsCtx) jsCtx {
s = bytes.TrimRight(s, "\t\n\f\r \u2028\u2029")
if len(s) == 0 {
return preceding
}
// All cases below are in the single-byte UTF-8 group.
switch c, n := s[len(s)-1], len(s); c {
case '+', '-':
// ++ and -- are not regexp preceders, but + and - are whether
// they are used as infix or prefix operators.
start := n - 1
// Count the number of adjacent dashes or pluses.
for start > 0 && s[start-1] == c {
start--
}
if (n-start)&1 == 1 {
// Reached for trailing minus signs since "---" is the
// same as "-- -".
return jsCtxRegexp
}
return jsCtxDivOp
case '.':
// Handle "42."
if n != 1 && '0' <= s[n-2] && s[n-2] <= '9' {
return jsCtxDivOp
}
return jsCtxRegexp
// Suffixes for all punctuators from section 7.7 of the language spec
// that only end binary operators not handled above.
case ',', '<', '>', '=', '*', '%', '&', '|', '^', '?':
return jsCtxRegexp
// Suffixes for all punctuators from section 7.7 of the language spec
// that are prefix operators not handled above.
case '!', '~':
return jsCtxRegexp
// Matches all the punctuators from section 7.7 of the language spec
// that are open brackets not handled above.
case '(', '[':
return jsCtxRegexp
// Matches all the punctuators from section 7.7 of the language spec
// that precede expression starts.
case ':', ';', '{':
return jsCtxRegexp
// CAVEAT: the close punctuators ('}', ']', ')') precede div ops and
// are handled in the default except for '}' which can precede a
// division op as in
// ({ valueOf: function () { return 42 } } / 2
// which is valid, but, in practice, developers don't divide object
// literals, so our heuristic works well for code like
// function () { ... } /foo/.test(x) && sideEffect();
// The ')' punctuator can precede a regular expression as in
// if (b) /foo/.test(x) && ...
// but this is much less likely than
// (a + b) / c
case '}':
return jsCtxRegexp
default:
// Look for an IdentifierName and see if it is a keyword that
// can precede a regular expression.
j := n
for j > 0 && isJSIdentPart(rune(s[j-1])) {
j--
}
if regexpPrecederKeywords[string(s[j:])] {
return jsCtxRegexp
}
}
// Otherwise is a punctuator not listed above, or
// a string which precedes a div op, or an identifier
// which precedes a div op.
return jsCtxDivOp
}
// regexpPrecederKeywords is a set of reserved JS keywords that can precede a
// regular expression in JS source.
var regexpPrecederKeywords = map[string]bool{
"break": true,
"case": true,
"continue": true,
"delete": true,
"do": true,
"else": true,
"finally": true,
"in": true,
"instanceof": true,
"return": true,
"throw": true,
"try": true,
"typeof": true,
"void": true,
}
var jsonMarshalType = reflect.TypeOf((*json.Marshaler)(nil)).Elem()
// indirectToJSONMarshaler returns the value, after dereferencing as many times
// as necessary to reach the base type (or nil) or an implementation of json.Marshal.
func indirectToJSONMarshaler(a interface{}) interface{} {
// text/template now supports passing untyped nil as a func call
// argument, so we must support it. Otherwise we'd panic below, as one
// cannot call the Type or Interface methods on an invalid
// reflect.Value. See golang.org/issue/18716.
if a == nil {
return nil
}
v := reflect.ValueOf(a)
for !v.Type().Implements(jsonMarshalType) && v.Kind() == reflect.Ptr && !v.IsNil() {
v = v.Elem()
}
return v.Interface()
}
// jsValEscaper escapes its inputs to a JS Expression (section 11.14) that has
// neither side-effects nor free variables outside (NaN, Infinity).
func jsValEscaper(args ...interface{}) string {
var a interface{}
if len(args) == 1 {
a = indirectToJSONMarshaler(args[0])
switch t := a.(type) {
case JS:
return string(t)
case JSStr:
// TODO: normalize quotes.
return `"` + string(t) + `"`
case json.Marshaler:
// Do not treat as a Stringer.
case fmt.Stringer:
a = t.String()
}
} else {
for i, arg := range args {
args[i] = indirectToJSONMarshaler(arg)
}
a = fmt.Sprint(args...)
}
// TODO: detect cycles before calling Marshal which loops infinitely on
// cyclic data. This may be an unacceptable DoS risk.
b, err := json.Marshal(a)
if err != nil {
// Put a space before comment so that if it is flush against
// a division operator it is not turned into a line comment:
// x/{{y}}
// turning into
// x//* error marshaling y:
// second line of error message */null
return fmt.Sprintf(" /* %s */null ", strings.ReplaceAll(err.Error(), "*/", "* /"))
}
// TODO: maybe post-process output to prevent it from containing
// "<!--", "-->", "<![CDATA[", "]]>", or "</script"
// in case custom marshalers produce output containing those.
// TODO: Maybe abbreviate \u00ab to \xab to produce more compact output.
if len(b) == 0 {
// In, `x=y/{{.}}*z` a json.Marshaler that produces "" should
// not cause the output `x=y/*z`.
return " null "
}
first, _ := utf8.DecodeRune(b)
last, _ := utf8.DecodeLastRune(b)
var buf strings.Builder
// Prevent IdentifierNames and NumericLiterals from running into
// keywords: in, instanceof, typeof, void
pad := isJSIdentPart(first) || isJSIdentPart(last)
if pad {
buf.WriteByte(' ')
}
written := 0
// Make sure that json.Marshal escapes codepoints U+2028 & U+2029
// so it falls within the subset of JSON which is valid JS.
for i := 0; i < len(b); {
rune, n := utf8.DecodeRune(b[i:])
repl := ""
if rune == 0x2028 {
repl = `\u2028`
} else if rune == 0x2029 {
repl = `\u2029`
}
if repl != "" {
buf.Write(b[written:i])
buf.WriteString(repl)
written = i + n
}
i += n
}
if buf.Len() != 0 {
buf.Write(b[written:])
if pad {
buf.WriteByte(' ')
}
return buf.String()
}
return string(b)
}
// jsStrEscaper produces a string that can be included between quotes in
// JavaScript source, in JavaScript embedded in an HTML5 <script> element,
// or in an HTML5 event handler attribute such as onclick.
func jsStrEscaper(args ...interface{}) string {
s, t := stringify(args...)
if t == contentTypeJSStr {
return replace(s, jsStrNormReplacementTable)
}
return replace(s, jsStrReplacementTable)
}
// jsRegexpEscaper behaves like jsStrEscaper but escapes regular expression
// specials so the result is treated literally when included in a regular
// expression literal. /foo{{.X}}bar/ matches the string "foo" followed by
// the literal text of {{.X}} followed by the string "bar".
func jsRegexpEscaper(args ...interface{}) string {
s, _ := stringify(args...)
s = replace(s, jsRegexpReplacementTable)
if s == "" {
// /{{.X}}/ should not produce a line comment when .X == "".
return "(?:)"
}
return s
}
// replace replaces each rune r of s with replacementTable[r], provided that
// r < len(replacementTable). If replacementTable[r] is the empty string then
// no replacement is made.
// It also replaces runes U+2028 and U+2029 with the raw strings `\u2028` and
// `\u2029`.
func replace(s string, replacementTable []string) string {
var b strings.Builder
r, w, written := rune(0), 0, 0
for i := 0; i < len(s); i += w {
// See comment in htmlEscaper.
r, w = utf8.DecodeRuneInString(s[i:])
var repl string
switch {
case int(r) < len(replacementTable) && replacementTable[r] != "":
repl = replacementTable[r]
case r == '\u2028':
repl = `\u2028`
case r == '\u2029':
repl = `\u2029`
default:
continue
}
if written == 0 {
b.Grow(len(s))
}
b.WriteString(s[written:i])
b.WriteString(repl)
written = i + w
}
if written == 0 {
return s
}
b.WriteString(s[written:])
return b.String()
}
var jsStrReplacementTable = []string{
0: `\0`,
'\t': `\t`,
'\n': `\n`,
'\v': `\x0b`, // "\v" == "v" on IE 6.
'\f': `\f`,
'\r': `\r`,
// Encode HTML specials as hex so the output can be embedded
// in HTML attributes without further encoding.
'"': `\x22`,
'&': `\x26`,
'\'': `\x27`,
'+': `\x2b`,
'/': `\/`,
'<': `\x3c`,
'>': `\x3e`,
'\\': `\\`,
}
// jsStrNormReplacementTable is like jsStrReplacementTable but does not
// overencode existing escapes since this table has no entry for `\`.
var jsStrNormReplacementTable = []string{
0: `\0`,
'\t': `\t`,
'\n': `\n`,
'\v': `\x0b`, // "\v" == "v" on IE 6.
'\f': `\f`,
'\r': `\r`,
// Encode HTML specials as hex so the output can be embedded
// in HTML attributes without further encoding.
'"': `\x22`,
'&': `\x26`,
'\'': `\x27`,
'+': `\x2b`,
'/': `\/`,
'<': `\x3c`,
'>': `\x3e`,
}
var jsRegexpReplacementTable = []string{
0: `\0`,
'\t': `\t`,
'\n': `\n`,
'\v': `\x0b`, // "\v" == "v" on IE 6.
'\f': `\f`,
'\r': `\r`,
// Encode HTML specials as hex so the output can be embedded
// in HTML attributes without further encoding.
'"': `\x22`,
'$': `\$`,
'&': `\x26`,
'\'': `\x27`,
'(': `\(`,
')': `\)`,
'*': `\*`,
'+': `\x2b`,
'-': `\-`,
'.': `\.`,
'/': `\/`,
'<': `\x3c`,
'>': `\x3e`,
'?': `\?`,
'[': `\[`,
'\\': `\\`,
']': `\]`,
'^': `\^`,
'{': `\{`,
'|': `\|`,
'}': `\}`,
}
// isJSIdentPart reports whether the given rune is a JS identifier part.
// It does not handle all the non-Latin letters, joiners, and combining marks,
// but it does handle every codepoint that can occur in a numeric literal or
// a keyword.
func isJSIdentPart(r rune) bool {
switch {
case r == '$':
return true
case '0' <= r && r <= '9':
return true
case 'A' <= r && r <= 'Z':
return true
case r == '_':
return true
case 'a' <= r && r <= 'z':
return true
}
return false
}
// isJSType reports whether the given MIME type should be considered JavaScript.
//
// It is used to determine whether a script tag with a type attribute is a javascript container.
func isJSType(mimeType string) bool {
// per
// https://www.w3.org/TR/html5/scripting-1.html#attr-script-type
// https://tools.ietf.org/html/rfc7231#section-3.1.1
// https://tools.ietf.org/html/rfc4329#section-3
// https://www.ietf.org/rfc/rfc4627.txt
mimeType = strings.ToLower(mimeType)
// discard parameters
if i := strings.Index(mimeType, ";"); i >= 0 {
mimeType = mimeType[:i]
}
mimeType = strings.TrimSpace(mimeType)
switch mimeType {
case
"application/ecmascript",
"application/javascript",
"application/json",
"application/ld+json",
"application/x-ecmascript",
"application/x-javascript",
"module",
"text/ecmascript",
"text/javascript",
"text/javascript1.0",
"text/javascript1.1",
"text/javascript1.2",
"text/javascript1.3",
"text/javascript1.4",
"text/javascript1.5",
"text/jscript",
"text/livescript",
"text/x-ecmascript",
"text/x-javascript":
return true
default:
return false
}
}
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