Drop unrecognized escape sequences instead of typing them

fzf consumed only the part of a sequence it recognized, and the rest was
typed into the query. CTRL-A sent as \e[97;5u became "97;5u". A
BEL-terminated OSC reply also aborted fzf, because the BEL that followed
the typed payload was read as CTRL-G.

Frame CSI and SS3 by their parameter and final byte ranges, OSC, DCS and APC
by their terminator, then drop the whole sequence when nothing matches it.
The second-chance read now runs only while a sequence is unfinished, since
after a complete one it blocked until the next keystroke.

Telling a terminal's sequence from an ALT key is the hard part, so several
shapes are deliberately left alone:

- An unterminated sequence, since that is how ALT-[, ALT-O, ALT-], ALT-P and
  ALT-_ arrive
- A CSI or SS3 short enough to be an ALT key with one or two characters typed
  after it
- A string sequence whose payload does not start like a reply: digits and
  ';' for OSC, '>|', '!|', '[01]$r' or '[01]+r' for DCS, 'G' and a key for
  APC. Otherwise typed text after ALT-], ALT-P or ALT-_, ended by CTRL-G or
  another key in the same read, framed like a reply and lost the abort
- SOS and PM, which nothing sends

Within a string, an ESC ends it and introduces a sequence of its own, so
scanning on to a later ST would swallow that one. Only OSC ends with BEL.
DCS and APC end with ST, and stopping at a BEL in their payload framed just
its first half.

The read loop does not wait for a string terminator. Waiting held ALT-],
ALT-P and ALT-_ for ESCDELAY and let typed bytes pile into the buffer until
they looked like a sequence.
This commit is contained in:
Junegunn Choi committed 2026-09-30 21:31:27 +09:00
1 parent b1be3a8be1
commit 55a69985d1
4 files changed
+359 -8

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+2
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@@ -4,6 +4,8 @@ CHANGELOG
0.74.5
------
- Fixed `--gap-line` cutting a grapheme cluster when filling the last cells of the line (#4920)
- Fixed an escape sequence fzf does not recognize being partly consumed, which leaked the rest into the query (#4926)
- A reply ending in BEL also aborted fzf, because the BEL was read as CTRL-G
0.74.4
------
+140 -8
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@@ -348,9 +348,105 @@ func getEnv(name string, defaultValue int) int {
func csiContinues(b byte) bool { return b >= 0x20 && b <= 0x3f }
func csiFinal(b byte) bool { return b >= 0x40 && b <= 0x7e }
// csiEnd returns the length of the CSI sequence at the start of the buffer, or
// 0 if it has no final byte yet or is malformed.
func csiEnd(buffer []byte) int {
for i := 2; i < len(buffer); i++ {
if csiFinal(buffer[i]) {
return i + 1
}
if !csiContinues(buffer[i]) {
return 0
}
}
return 0
}
// stringEnd returns the length of the string sequence (DCS, OSC or APC) at the
// start of the buffer, up to and including whatever ended it, or 0 while nothing
// has.
func stringEnd(buffer []byte) int {
if len(buffer) < 2 {
return 0
}
// Every one of them ends with ST. BEL ends an OSC as well, because xterm has
// always allowed it, but stopping at a BEL inside a DCS or APC payload would
// frame only its first half and leave the rest to be typed into the query.
bel := buffer[1] == ']'
for i := 2; i < len(buffer); i++ {
switch buffer[i] {
case '\a':
if bel {
return i + 1
}
case Esc.Byte():
if i+1 == len(buffer) {
return 0 // ST may still be arriving
}
if buffer[i+1] == '\\' {
return i + 2
}
// Any other ESC ends the string and introduces a sequence of its
// own, so frame only what precedes it and leave the ESC to be
// parsed again. Scanning past it would swallow that sequence too.
return i
}
}
return 0
}
// csiIntroducer reports whether the byte after ESC starts a sequence that is
// framed by a final byte. The parser routes CSI and SS3 through the same
// parameterized subcases, so both are framed by csiEnd.
func csiIntroducer(b byte) bool {
return b == '[' || b == 'O'
}
// stringIntroducer reports whether the byte after ESC starts a string sequence.
// Only the three that terminals reply with: OSC for colors, title and clipboard,
// DCS for XTVERSION, DECRQSS and XTGETTCAP, APC for Kitty graphics. Nothing
// sends SOS or PM.
func stringIntroducer(b byte) bool {
switch b {
case 'P', ']', '_':
return true
}
return false
}
// stringReply reports whether a framed string sequence starts the way a
// terminal's reply does. Its introducer is also ALT-], ALT-P or ALT-_, and typed
// text after one, ended by CTRL-G or another key, frames like a reply when it
// all arrives in one read.
func stringReply(buffer []byte) bool {
payload := buffer[2:]
switch buffer[1] {
case ']': // Ps ; ...
i := 0
for i < len(payload) && payload[i] >= '0' && payload[i] <= '9' {
i++
}
return i > 0 && i < len(payload) && payload[i] == ';'
case 'P': // >| or !| for the version, [01]$r or [01]+r for settings
if len(payload) < 2 {
return false
}
if payload[1] == '|' {
return payload[0] == '>' || payload[0] == '!'
}
return len(payload) >= 3 && (payload[0] == '0' || payload[0] == '1') &&
(payload[1] == '$' || payload[1] == '+') && payload[2] == 'r'
case '_': // G, then key=value
return len(payload) >= 3 && payload[0] == 'G' &&
(payload[1] >= 'a' && payload[1] <= 'z' || payload[1] >= 'A' && payload[1] <= 'Z') &&
payload[2] == '='
}
return false
}
// incompleteEscape reports whether the buffer ends in an escape sequence that
// has not been terminated yet. The read loop keeps waiting in that case, so the
// parser is never handed a fragment to guess at.
// has not been terminated yet. The read loop keeps waiting while it does, so a
// fragment reaches the parser only once that wait has run out.
func incompleteEscape(buffer []byte) bool {
// Only the tail can hold a sequence still arriving. This runs once per byte
// read, so scanning all of a large paste would make the read quadratic.
@@ -362,8 +458,9 @@ func incompleteEscape(buffer []byte) bool {
if start < 0 || len(tail)-start < 2 {
return false
}
switch tail[start+1] {
case '[':
// Declaring SS3 finished after one byte made the parser give up on a split
// \eO1;5A and type its tail into the query.
if csiIntroducer(tail[start+1]) {
for _, b := range tail[start+2:] {
if csiFinal(b) {
return false
@@ -373,8 +470,6 @@ func incompleteEscape(buffer []byte) bool {
}
}
return true
case 'O':
return len(tail)-start < 3
}
return false
}
@@ -483,8 +578,10 @@ func (r *LightRenderer) GetChar(cancellable bool) Event {
return Event{CtrlSlash, 0, nil}
case Esc.Byte():
ev := r.escSequence(&sz)
// Second chance
if ev.Type == Invalid {
// Second chance, but only while the buffer ends in an unfinished
// sequence. Re-reading otherwise blocks until the next keystroke,
// holding back whatever follows in the buffer.
if ev.Type == Invalid && incompleteEscape(r.buffer) {
r.buffer, result, err = r.getBytes(true)
if err != nil {
return Event{Fatal, 0, nil}
@@ -525,7 +622,24 @@ func (r *LightRenderer) setCancel(f func()) {
r.mutex.Unlock()
}
// escSequence parses an escape sequence, widening a CSI or SS3 sequence that
// parseEscSequence recognized the start of but gave up on partway. Consuming
// only the part that parsed would leave the rest to be read as input and typed
// into the query. Complete sequences it does not recognize are dropped there.
func (r *LightRenderer) escSequence(sz *int) Event {
ev := r.parseEscSequence(sz)
if ev.Type != Invalid || len(r.buffer) < 3 || !csiIntroducer(r.buffer[1]) {
return ev
}
// Only a framed sequence is dropped. One still missing its final byte may
// yet be arriving, and the caller gives it another chance.
if end := csiEnd(r.buffer); end > *sz {
*sz = end
}
return ev
}
func (r *LightRenderer) parseEscSequence(sz *int) Event {
if len(r.buffer) < 2 {
return Event{Esc, 0, nil}
}
@@ -987,6 +1101,24 @@ func (r *LightRenderer) escSequence(sz *int) Event {
} // r.buffer[2]
} // r.buffer[2]
} // r.buffer[1]
// Nothing matched. A framed sequence is dropped whole: reading its
// introducer as an ALT-key below would type the rest into the query.
// Unterminated ones are left alone, as that is how ALT-[, ALT-O, ALT-],
// ALT-P and ALT-_ arrive.
if csiIntroducer(r.buffer[1]) {
// ALT-[ or ALT-O and one or two typed characters can look like a short
// sequence, so ask for more than one parameter byte before dropping it
if end := csiEnd(r.buffer); end > 4 {
*sz = end
return Event{Invalid, 0, nil}
}
} else if stringIntroducer(r.buffer[1]) {
if end := stringEnd(r.buffer); end > 0 && stringReply(r.buffer) {
*sz = end
return Event{Invalid, 0, nil}
}
}
rest := bytes.NewBuffer(r.buffer[1:])
c, size, err := rest.ReadRune()
if err == nil {
+177
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@@ -0,0 +1,177 @@
package tui
import "testing"
// An unrecognized escape sequence must be consumed whole, CSI and string
// sequences alike. Consuming only part of one leaves the rest to be read as
// input and typed into the query.
func TestUnknownEscapeSequence(t *testing.T) {
for _, c := range []struct {
sequence string
event EventType
size int
}{
// Key encodings fzf does not implement
{"\x1b[97;5u", Invalid, 7},
{"\x1b[127;5u", Invalid, 8},
{"\x1b[27;5;127~", Invalid, 11},
{"\x1b[57441;1u", Invalid, 10},
{"\x1b\x1b[97;5u", Invalid, 7}, // ALT prefixed, the first ESC is dropped
// Replies to queries fzf did not send, or sent and stopped waiting for
{"\x1b[?1;2c", Invalid, 7},
{"\x1b[>0;95;0c", Invalid, 10},
// Mouse report arriving while mouse input is off
{"\x1b[<0;1;1M", Invalid, 9},
// String sequences
{"\x1b]11;rgb:4a4a/4a4a/4a4a\x1b\\", Invalid, 25}, // background color reply
{"\x1b]0;a title\a", Invalid, 12}, // BEL terminated
{"\x1bP>|kitty(0.48.2)\x1b\\", Invalid, 19}, // XTVERSION reply
{"\x1b_Gi=1;OK\x1b\\", Invalid, 11}, // Kitty graphics reply
{"\x1bP1$r\a\x1b\\", Invalid, 8}, // BEL is payload in a DCS
{"\x1b]11;x\x1bX\x1b\\", Invalid, 6}, // ESC ends it, framing "\e]11;x"
// SS3 is framed like CSI, since the parser routes both the same way
{"\x1bO9;5u", Invalid, 6},
{"\x1bO1;5X", Invalid, 6}, // unknown final byte
{"\x1bO1;5A", CtrlUp, 6}, // recognized, unchanged
{"\x1bOP", F1, 3},
// Left alone: this is how ALT-[, ALT-O, ALT-], ALT-P and ALT-_ arrive
{"\x1b[a", Alt, 2},
{"\x1b[9A", Alt, 2}, // ALT-[ and two characters can look like a CSI
{"\x1b[1m", Alt, 2},
{"\x1b[ x", Alt, 2},
{"\x1bOx", Alt, 2},
{"\x1bO9A", Alt, 2},
{"\x1b]abc", Alt, 2},
{"\x1b]11;rgb:", Alt, 2}, // terminator has not arrived
{"\x1b]\x1b]", Alt, 2}, // a second sequence must not swallow the ALT key
{"\x1b]\x1b[A", Alt, 2},
{"\x1bP\x1bP", Alt, 2},
{"\x1b_\x1b_", Alt, 2},
{"\x1b]\x1b\\", Alt, 2}, // ALT-] then ALT-backslash, not an empty OSC
{"\x1b]\a", Alt, 2}, // ALT-] then CTRL-G, which must still abort
// Typed text after the introducer is not a reply, even when a
// terminator follows in the same read
{"\x1b]a\a", Alt, 2},
{"\x1b]1\a", Alt, 2},
{"\x1b]a\x1b[A", Alt, 2},
{"\x1bPx\x1b[A", Alt, 2},
{"\x1b_ab\x1bb", Alt, 2},
// SOS and PM are not framed
{"\x1bXsos\x1b\\", Alt, 2},
{"\x1b^status\x1b\\", Alt, 2},
// Left alone: no final byte yet, so the sequence may still be arriving
{"\x1b[", Invalid, 2},
// Recognized sequences keep their existing parsing
{"\x1b[1;5A", CtrlUp, 6},
{"\x1b[3;5~", CtrlDelete, 6},
{"\x1b[2~", Insert, 4},
{"\x1b[200~", BracketedPasteBegin, 6},
{"\x1b[Z", ShiftTab, 3},
{"\x1bOA", Up, 3},
{"\x1b[12;34R", Invalid, 8},
{"\x1b[?2004;2$y", Invalid, 11},
} {
r := &LightRenderer{buffer: []byte(c.sequence)}
sz := 1
event := r.escSequence(&sz)
if event.Type != c.event {
t.Errorf("escSequence(%q) = %s, want %s",
c.sequence, event.Type.String(), c.event.String())
}
if sz != c.size {
t.Errorf("escSequence(%q) consumed %d bytes, want %d", c.sequence, sz, c.size)
}
}
}
func TestStringEnd(t *testing.T) {
for _, c := range []struct {
buffer string
want int
}{
// Terminated
{"\x1b]0;t\a", 6},
{"\x1b]0;t\x1b\\", 7},
{"\x1b_G\x1b\\", 5},
{"\x1bP1$r\a\x1b\\", 8}, // BEL is payload in a DCS, ST ends it
// BEL terminates an OSC only
{"\x1bP\a", 0},
{"\x1b_Gi=1\a", 0},
// An ESC ends the string and introduces a sequence of its own
{"\x1b]foo\x1bX\x1b\\", 5},
{"\x1b]foo\x1bP", 5},
{"\x1b]\x1b]", 2},
// Nothing has ended it yet
{"\x1b]0;t", 0},
{"\x1b]0;t\x1b", 0}, // ST half arrived
{"\x1b]foo\x1b", 0},
{"\x1b]", 0},
{"\x1b", 0}, // shorter than an introducer
} {
if got := stringEnd([]byte(c.buffer)); got != c.want {
t.Errorf("stringEnd(%q) = %d, want %d", c.buffer, got, c.want)
}
}
}
func TestStringReply(t *testing.T) {
for _, c := range []struct {
buffer string
want bool
}{
{"\x1b]11;rgb:1/2/3\a", true},
{"\x1b]0;title\a", true},
{"\x1b]52;c;YWJj\x1b\\", true},
{"\x1bP>|kitty(0.48.2)\x1b\\", true},
{"\x1bP!|0\x1b\\", true},
{"\x1bP1$r0m\x1b\\", true},
{"\x1bP0+r\x1b\\", true},
{"\x1b_Gi=1;OK\x1b\\", true},
// What typed text after ALT-], ALT-P or ALT-_ looks like
{"\x1b]\a", false},
{"\x1b]a\a", false},
{"\x1b]1\a", false},
{"\x1b];\a", false},
{"\x1bPx\x1b\\", false},
{"\x1bP1\x1b\\", false},
{"\x1b_ab\x1b\\", false},
{"\x1b_G\x1b\\", false},
} {
if got := stringReply([]byte(c.buffer)); got != c.want {
t.Errorf("stringReply(%q) = %v, want %v", c.buffer, got, c.want)
}
}
}
func TestCsiEnd(t *testing.T) {
for _, c := range []struct {
buffer string
want int
}{
{"\x1b[97;5u", 7},
{"\x1b[A", 3},
{"\x1b[<0;1;1M", 9},
{"\x1b[?2004;2$y", 11},
{"\x1b[97;5", 0}, // no final byte
{"\x1b[", 0}, // no final byte
{"\x1b[1\x01A", 0}, // malformed, do not frame it
} {
if got := csiEnd([]byte(c.buffer)); got != c.want {
t.Errorf("csiEnd(%q) = %d, want %d", c.buffer, got, c.want)
}
}
}
+40
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@@ -51,3 +51,43 @@ func TestIncompleteEscape(t *testing.T) {
}
}
}
// A string sequence is not waited for. Its introducer is also ALT-], ALT-P or
// ALT-_, and holding the read open on those both delayed the key and let typed
// bytes accumulate into something that looked like a sequence.
func TestIncompleteStringEscape(t *testing.T) {
for _, buffer := range []string{
"\x1b]11;rgb:",
"\x1bP>|kitty",
"\x1b_Gi=1",
"\x1b]0;t\x1b",
"\x1b]0;title\a",
"ab\x1b]11;rgb:",
} {
if incompleteEscape([]byte(buffer)) {
t.Errorf("incompleteEscape(%q) = true, want false", buffer)
}
}
}
// SS3 reaches the same parameterized subcases as CSI in the parser, so it has to
// be judged the same way here. Declaring it finished after one byte made the
// parser give up on a split \eO1;5A and type its tail into the query.
func TestIncompleteSS3(t *testing.T) {
for _, c := range []struct {
buffer string
want bool
}{
{"\x1bO", true},
{"\x1bO1", true},
{"\x1bO1;", true},
{"\x1bO1;5", true},
{"\x1bOA", false},
{"\x1bOP", false},
{"\x1bO1;5A", false},
} {
if got := incompleteEscape([]byte(c.buffer)); got != c.want {
t.Errorf("incompleteEscape(%q) = %v, want %v", c.buffer, got, c.want)
}
}
}