Update to last common x/text (#3994)

vendor/golang.org/x/text/encoding/japanese/iso2022jp.go

@@ -5,7 +5,6 @@
 package japanese
 
 import (
-	"errors"
 	"unicode/utf8"
 
 	"golang.org/x/text/encoding"
@@ -31,8 +30,6 @@ func iso2022JPNewEncoder() transform.Transformer {
 	return new(iso2022JPEncoder)
 }
 
-var errInvalidISO2022JP = errors.New("japanese: invalid ISO-2022-JP encoding")
-
 const (
 	asciiState = iota
 	katakanaState
@@ -50,45 +47,51 @@ func (d *iso2022JPDecoder) Reset() {
 
 func (d *iso2022JPDecoder) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
 	r, size := rune(0), 0
-loop:
 	for ; nSrc < len(src); nSrc += size {
 		c0 := src[nSrc]
 		if c0 >= utf8.RuneSelf {
-			err = errInvalidISO2022JP
-			break loop
+			r, size = '\ufffd', 1
+			goto write
 		}
 
 		if c0 == asciiEsc {
 			if nSrc+2 >= len(src) {
-				err = transform.ErrShortSrc
-				break loop
+				if !atEOF {
+					return nDst, nSrc, transform.ErrShortSrc
+				}
+				// TODO: is it correct to only skip 1??
+				r, size = '\ufffd', 1
+				goto write
 			}
 			size = 3
 			c1 := src[nSrc+1]
 			c2 := src[nSrc+2]
 			switch {
-			case c1 == '$' && (c2 == '@' || c2 == 'B'):
+			case c1 == '$' && (c2 == '@' || c2 == 'B'): // 0x24 {0x40, 0x42}
 				*d = jis0208State
 				continue
-			case c1 == '$' && c2 == '(':
+			case c1 == '$' && c2 == '(': // 0x24 0x28
 				if nSrc+3 >= len(src) {
-					err = transform.ErrShortSrc
-					break loop
+					if !atEOF {
+						return nDst, nSrc, transform.ErrShortSrc
+					}
+					r, size = '\ufffd', 1
+					goto write
 				}
 				size = 4
-				if src[nSrc]+3 == 'D' {
+				if src[nSrc+3] == 'D' {
 					*d = jis0212State
 					continue
 				}
-			case c1 == '(' && (c2 == 'B' || c2 == 'J'):
+			case c1 == '(' && (c2 == 'B' || c2 == 'J'): // 0x28 {0x42, 0x4A}
 				*d = asciiState
 				continue
-			case c1 == '(' && c2 == 'I':
+			case c1 == '(' && c2 == 'I': // 0x28 0x49
 				*d = katakanaState
 				continue
 			}
-			err = errInvalidISO2022JP
-			break loop
+			r, size = '\ufffd', 1
+			goto write
 		}
 
 		switch *d {
@@ -97,8 +100,8 @@ loop:
 
 		case katakanaState:
 			if c0 < 0x21 || 0x60 <= c0 {
-				err = errInvalidISO2022JP
-				break loop
+				r, size = '\ufffd', 1
+				goto write
 			}
 			r, size = rune(c0)+(0xff61-0x21), 1
 
@@ -106,11 +109,14 @@ loop:
 			if c0 == 0x0a {
 				*d = asciiState
 				r, size = rune(c0), 1
-				break
+				goto write
 			}
 			if nSrc+1 >= len(src) {
-				err = transform.ErrShortSrc
-				break loop
+				if !atEOF {
+					return nDst, nSrc, transform.ErrShortSrc
+				}
+				r, size = '\ufffd', 1
+				goto write
 			}
 			size = 2
 			c1 := src[nSrc+1]
@@ -121,22 +127,19 @@ loop:
 				r = rune(jis0212Decode[i])
 			} else {
 				r = '\ufffd'
-				break
+				goto write
 			}
 			if r == 0 {
 				r = '\ufffd'
 			}
 		}
 
+	write:
 		if nDst+utf8.RuneLen(r) > len(dst) {
-			err = transform.ErrShortDst
-			break loop
+			return nDst, nSrc, transform.ErrShortDst
 		}
 		nDst += utf8.EncodeRune(dst[nDst:], r)
 	}
-	if atEOF && err == transform.ErrShortSrc {
-		err = errInvalidISO2022JP
-	}
 	return nDst, nSrc, err
 }