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Add support for Jujutsu conflict markers #64750

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45 changes: 36 additions & 9 deletions tsc/internal/scanner/scanner.go
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Original file line number Diff line number Diff line change
Expand Up @@ -530,6 +530,15 @@ func (s *Scanner) Scan() ast.Kind {
case '`':
s.token = s.scanTemplateAndSetTokenValue(false /*shouldEmitInvalidEscapeError*/)
case '%':
if s.charAt(1) == '%' && isConflictMarkerTrivia(s.text, s.pos) {
s.pos = scanConflictMarkerTrivia(s.text, s.pos, s.errorAt)

@jakebailey Jake Bailey (jakebailey) Oct 13, 2026

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I think this still misses Jujutsu’s longer markers, e.g. %%%%%%%%%%%%%%% diff from: base, because the existing check expects a space after the seventh character.

https://docs.jj-vcs.dev/latest/conflicts/#long-conflict-markers

@jakebailey Jake Bailey (jakebailey) Oct 13, 2026

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Actually, I think just accepting “seven or more” characters would still be problematic: jj lengthens markers so shorter marker-like lines can remain ordinary content. For example, =========== can appear inside a conflict delimited by fifteen-character markers, so we’d need to match the delimiter width.

@rf- Ryan Fitzgerald (rf-) Oct 14, 2026

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Actually, I think just accepting “seven or more” characters would still be problematic: jj lengthens markers so shorter marker-like lines can remain ordinary content. For example, =========== can appear inside a conflict delimited by fifteen-character markers, so we’d need to match the delimiter width.

Hmm, I wonder if this is really necessary. TS doesn't try to account for ambiguous/misleading markers in its current Git support, right?

I guess it's possible to construct a situation where a >>>>>>> inside a string or whatever tricks the parser into thinking it's a conflict marker, but it seems really unlikely to happen by accident, and the consequences wouldn't be that bad. I'm not sure if it's worth adding extra state in the scanner just to avoid it.

@jakebailey Jake Bailey (jakebailey) Oct 14, 2026

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Maybe it's not worth it if it rarely happens; I was just reading up the docs since I wasn't sure what stuff jj did extra over git.

if s.skipTrivia {
continue
} else {
s.token = ast.KindConflictMarkerTrivia
return s.token
}
}
if s.charAt(1) == '=' {
s.pos += 2
s.token = ast.KindPercentEqualsToken
Expand Down Expand Up @@ -584,6 +593,15 @@ func (s *Scanner) Scan() ast.Kind {
s.token = ast.KindAsteriskToken
}
case '+':
if s.charAt(1) == '+' && isConflictMarkerTrivia(s.text, s.pos) {
s.pos = scanConflictMarkerTrivia(s.text, s.pos, s.errorAt)
if s.skipTrivia {
continue
} else {
s.token = ast.KindConflictMarkerTrivia
return s.token
}
}
next := s.charAt(1)
if next == '=' {
s.pos += 2
Expand Down Expand Up @@ -896,6 +914,15 @@ func (s *Scanner) Scan() ast.Kind {
s.pos++
s.token = ast.KindAtToken
case '\\':
if s.charAt(1) == '\\' && isConflictMarkerTrivia(s.text, s.pos) {
s.pos = scanConflictMarkerTrivia(s.text, s.pos, s.errorAt)
if s.skipTrivia {
continue
} else {
s.token = ast.KindConflictMarkerTrivia
return s.token
}
}
if s.scanIdentifier(0, identifierVariantStandard) {
s.token = GetIdentifierToken(s.tokenValue)
} else {
Expand Down Expand Up @@ -2288,7 +2315,7 @@ func couldStartTrivia(text string, pos int) bool {
// Characters that could start normal trivia
case '\r', '\n', '\t', '\v', '\f', ' ', '/',
// Characters that could start conflict marker trivia
'<', '|', '=', '>':
'<', '|', '=', '%', '\\', '+', '>':
return true
case '#':
// Only if its the beginning can we have #! trivia
Expand Down Expand Up @@ -2371,7 +2398,7 @@ func SkipTriviaEx(text string, pos int, options *SkipTriviaOptions) int {
continue
}
}
case '<', '|', '=', '>':
case '<', '|', '=', '%', '\\', '+', '>':
if isConflictMarkerTrivia(text, pos) {
pos = scanConflictMarkerTrivia(text, pos, nil)
canConsumeStar = false
Expand Down Expand Up @@ -2412,8 +2439,8 @@ func isConflictMarkerTrivia(text string, pos int) bool {
}

// Fast reject: a conflict marker is the same byte repeated seven times. If the
// second byte differs (the overwhelmingly common case for `<`, `>`, `=`, `|`
// tokens), it cannot be a marker, so skip the line-start check entirely.
// second byte differs (the overwhelmingly common case), it cannot be a marker,
// so skip the line-start check entirely.
if pos+1 >= len(text) || text[pos+1] != text[pos] {
return false
}
Expand Down Expand Up @@ -2454,14 +2481,14 @@ func scanConflictMarkerTrivia(text string, pos int, reportError func(diag *diagn
ch, size = utf8.DecodeRuneInString(text[pos:])
}
} else {
if ch != '|' && ch != '=' {
panic("Assertion failed: ch must be either '|' or '='")
if ch != '|' && ch != '=' && ch != '%' && ch != '\\' && ch != '+' {
panic("Assertion failed: ch must be '|', '=', '%', '\\', or '+'")
}
// Consume everything from the start of a ||||||| or ======= marker to the start
// of the next ======= or >>>>>>> marker.
// Consume everything from the start of an intermediate marker to the
// start of the next intermediate marker or the overall >>>>>>> marker.
for pos < length {
currentChar := text[pos]
if (currentChar == '=' || currentChar == '>') && rune(currentChar) != ch && isConflictMarkerTrivia(text, pos) {
if (currentChar == '=' || currentChar == '%' || currentChar == '\\' || currentChar == '+' || currentChar == '>') && rune(currentChar) != ch && isConflictMarkerTrivia(text, pos) {

@jakebailey Jake Bailey (jakebailey) Oct 13, 2026

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I believe snapshot style is also missing some delimiter diagnostics. In this example, ------- and the second +++++++ get swallowed by the first snapshot section:

<<<<<<< conflict 1 of 1
+++++++ ours
ours();
------- base
base();
+++++++ theirs
theirs();
>>>>>>> conflict 1 of 1 ends

https://docs.jj-vcs.dev/latest/conflicts/#alternative-conflict-marker-styles

@jakebailey Jake Bailey (jakebailey) Oct 13, 2026

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I believe this also affects ui.conflict-marker-style = "git", since jj falls back to snapshot style for conflicts with more than two sides?

@rf- Ryan Fitzgerald (rf-) Oct 14, 2026

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Yep, this is easy to fix by adding -, thanks for flagging.

break
}

Expand Down
33 changes: 33 additions & 0 deletions tsc/testdata/baselines/reference/compiler/conflictMarkerJujutsuTrivia1.errors.txt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
conflictMarkerJujutsuTrivia1.ts(3,1): error TS1185: Merge conflict marker encountered.
conflictMarkerJujutsuTrivia1.ts(4,1): error TS1185: Merge conflict marker encountered.
conflictMarkerJujutsuTrivia1.ts(5,1): error TS1185: Merge conflict marker encountered.
conflictMarkerJujutsuTrivia1.ts(8,1): error TS1185: Merge conflict marker encountered.
conflictMarkerJujutsuTrivia1.ts(10,1): error TS1185: Merge conflict marker encountered.


==== conflictMarkerJujutsuTrivia1.ts (5 errors) ====
class C {
foo() {
<<<<<<< conflict 1 of 1
~~~~~~~
!!! error TS1185: Merge conflict marker encountered.
%%%%%%% diff from: puqzxvrm 9be6077e "call c()"
~~~~~~~
!!! error TS1185: Merge conflict marker encountered.
\\\\\\\ to: lnqukurm 3504bbcc "call a()"
~~~~~~~
!!! error TS1185: Merge conflict marker encountered.
- c();
+ a();
+++++++ uxvuvmmx 392ce8b5 "call b()"
~~~~~~~
!!! error TS1185: Merge conflict marker encountered.
b();
>>>>>>> conflict 1 of 1 ends
~~~~~~~
!!! error TS1185: Merge conflict marker encountered.
}

public bar() { }
}

26 changes: 26 additions & 0 deletions tsc/testdata/baselines/reference/compiler/conflictMarkerJujutsuTrivia1.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,26 @@
//// [tests/cases/compiler/conflictMarkerJujutsuTrivia1.ts] ////

//// [conflictMarkerJujutsuTrivia1.ts]
class C {
foo() {
<<<<<<< conflict 1 of 1
%%%%%%% diff from: puqzxvrm 9be6077e "call c()"
\\\\\\\ to: lnqukurm 3504bbcc "call a()"
- c();
+ a();
+++++++ uxvuvmmx 392ce8b5 "call b()"
b();
>>>>>>> conflict 1 of 1 ends
}

public bar() { }
}


//// [conflictMarkerJujutsuTrivia1.js]
"use strict";
class C {
foo() {
}
bar() { }
}
23 changes: 23 additions & 0 deletions tsc/testdata/baselines/reference/compiler/conflictMarkerJujutsuTrivia1.symbols
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
//// [tests/cases/compiler/conflictMarkerJujutsuTrivia1.ts] ////

=== conflictMarkerJujutsuTrivia1.ts ===
class C {
>C : Symbol(C, Decl(conflictMarkerJujutsuTrivia1.ts, 0, 0))

foo() {
>foo : Symbol(C.foo, Decl(conflictMarkerJujutsuTrivia1.ts, 0, 9))

<<<<<<< conflict 1 of 1
%%%%%%% diff from: puqzxvrm 9be6077e "call c()"
\\\\\\\ to: lnqukurm 3504bbcc "call a()"
- c();
+ a();
+++++++ uxvuvmmx 392ce8b5 "call b()"
b();
>>>>>>> conflict 1 of 1 ends
}

public bar() { }
>bar : Symbol(C.bar, Decl(conflictMarkerJujutsuTrivia1.ts, 10, 3))
}

23 changes: 23 additions & 0 deletions tsc/testdata/baselines/reference/compiler/conflictMarkerJujutsuTrivia1.types
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
//// [tests/cases/compiler/conflictMarkerJujutsuTrivia1.ts] ////

=== conflictMarkerJujutsuTrivia1.ts ===
class C {
>C : C

foo() {
>foo : () => void

<<<<<<< conflict 1 of 1
%%%%%%% diff from: puqzxvrm 9be6077e "call c()"
\\\\\\\ to: lnqukurm 3504bbcc "call a()"
- c();
+ a();
+++++++ uxvuvmmx 392ce8b5 "call b()"
b();
>>>>>>> conflict 1 of 1 ends
}

public bar() { }
>bar : () => void
}

15 changes: 15 additions & 0 deletions tsc/testdata/tests/cases/compiler/conflictMarkerJujutsuTrivia1.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
// @target: es2015
class C {
foo() {
<<<<<<< conflict 1 of 1
%%%%%%% diff from: puqzxvrm 9be6077e "call c()"
\\\\\\\ to: lnqukurm 3504bbcc "call a()"
- c();
+ a();
+++++++ uxvuvmmx 392ce8b5 "call b()"
b();
>>>>>>> conflict 1 of 1 ends

@jakebailey Jake Bailey (jakebailey) Oct 13, 2026

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I think the missing-newline example would be useful coverage too: it puts +++++++ before %%%%%%% and ends the >>>>>>> line at EOF without a newline.

https://docs.jj-vcs.dev/latest/conflicts/#conflicts-with-missing-terminating-newline

}

public bar() { }
}
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