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Fix RegExp lookbehind direction #673

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Merged
frostney merged 3 commits into from
May 20, 2026
+258 −47
Merged

Fix RegExp lookbehind direction #673

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b1b8de5
Fix RegExp lookbehind direction
frostney May 20, 2026
1924d7b
Merge remote-tracking branch 'origin/main' into issue-612-regexp-look…
frostney May 20, 2026
59f5b6d
Address RegExp lookbehind review comments
frostney May 20, 2026
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90 changes: 84 additions & 6 deletions source/units/Goccia.RegExp.Compiler.pas
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,12 @@ TRegExpStringSequence = record
CodePoints: array of Cardinal;
end;

TRegExpTermCode = record
Code: array of UInt32;
Length: Integer;
OriginalStart: Integer;
end;

TRegExpClassContents = record
Ranges: array of TRegExpCharRange;
RangeCount: Integer;
Expand All @@ -104,6 +110,7 @@ TRegExpCompiler = class
FUnicode: Boolean;
FUnicodeSets: Boolean;
FPendingCodeUnit: Integer;
FBackward: Boolean;
function Peek: Char;
function PeekAt(AOffset: Integer): Char;
function AtEnd: Boolean;
Expand Down Expand Up @@ -328,6 +335,7 @@ constructor TRegExpCompiler.Create(const APattern, AFlags: string);
FUnicodeSets := HasRegExpFlag(AFlags, 'v');
FUnicode := HasRegExpFlag(AFlags, 'u') or FUnicodeSets;
FPendingCodeUnit := -1;
FBackward := False;
end;

function TRegExpCompiler.Peek: Char;
Expand Down Expand Up @@ -1530,8 +1538,16 @@ procedure TRegExpCompiler.EmitClassContents(
SplitHoles[SplitCount] := CurrentPC;
Inc(SplitCount);
Emit(EncodeOpBx(RX_SPLIT, 0));
for J := 0 to High(AContents.Strings[I].CodePoints) do
EmitCharMatch(AContents.Strings[I].CodePoints[J]);
if FBackward then
begin
for J := High(AContents.Strings[I].CodePoints) downto 0 do
EmitCharMatch(AContents.Strings[I].CodePoints[J]);
end
else
begin
for J := 0 to High(AContents.Strings[I].CodePoints) do
EmitCharMatch(AContents.Strings[I].CodePoints[J]);
end;
JumpHoles[JumpCount] := CurrentPC;
Inc(JumpCount);
Emit(EncodeOpBx(RX_JUMP, 0));
Expand Down Expand Up @@ -2106,6 +2122,7 @@ procedure TRegExpCompiler.CompileModifierGroup;
procedure TRegExpCompiler.CompileGroup;
var
SaveAltDepth: Integer;
SavedBackward: Boolean;
GroupName: string;
CaptureIdx, I: Integer;
SplitHole, JumpHole: Integer;
Expand All @@ -2128,8 +2145,11 @@ procedure TRegExpCompiler.CompileGroup;
begin
SplitHole := EmitHole;
FCode[SplitHole] := EncodeOpBx(RX_LOOKAHEAD, 0);
SavedBackward := FBackward;
FBackward := False;
LookStart := CurrentPC;
CompileDisjunction;
FBackward := SavedBackward;
if not Match(')') then
raise EConvertError.Create('Unterminated lookahead');
Emit(EncodeOp(RX_MATCH));
Expand All @@ -2140,7 +2160,10 @@ procedure TRegExpCompiler.CompileGroup;
begin
SplitHole := EmitHole;
FCode[SplitHole] := EncodeOpBx(RX_LOOKAHEAD, 0);
SavedBackward := FBackward;
FBackward := False;
CompileDisjunction;
FBackward := SavedBackward;
if not Match(')') then
raise EConvertError.Create('Unterminated negative lookahead');
Emit(EncodeOp(RX_MATCH));
Expand All @@ -2153,7 +2176,10 @@ procedure TRegExpCompiler.CompileGroup;
begin
SplitHole := EmitHole;
FCode[SplitHole] := EncodeOpBx(RX_LOOKBEHIND, 0);
SavedBackward := FBackward;
FBackward := True;
CompileDisjunction;
FBackward := SavedBackward;
if not Match(')') then
raise EConvertError.Create('Unterminated lookbehind');
Emit(EncodeOp(RX_MATCH));
Expand All @@ -2164,7 +2190,10 @@ procedure TRegExpCompiler.CompileGroup;
begin
SplitHole := EmitHole;
FCode[SplitHole] := EncodeOpBx(RX_LOOKBEHIND, 0);
SavedBackward := FBackward;
FBackward := True;
CompileDisjunction;
FBackward := SavedBackward;
if not Match(')') then
raise EConvertError.Create('Unterminated negative lookbehind');
Emit(EncodeOp(RX_MATCH));
Expand All @@ -2176,11 +2205,18 @@ procedure TRegExpCompiler.CompileGroup;
GroupName := ParseGroupName;
Inc(FCaptureCount);
CaptureIdx := FCaptureCount;
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2));
// Backward capture groups still store source-order [start, end] slots.
if FBackward then
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2 + 1))
else
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2));
CompileDisjunction;
if not Match(')') then
raise EConvertError.Create('Unterminated named capture group');
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2 + 1));
if FBackward then
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2))
else
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2 + 1));
end;
end
else if CharInSet(Peek, ['i', 'm', 's', '-']) then
Expand All @@ -2194,11 +2230,18 @@ procedure TRegExpCompiler.CompileGroup;
begin
Inc(FCaptureCount);
CaptureIdx := FCaptureCount;
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2));
// Backward capture groups still store source-order [start, end] slots.
if FBackward then
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2 + 1))
else
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2));
CompileDisjunction;
if not Match(')') then
raise EConvertError.Create('Unterminated capturing group');
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2 + 1));
if FBackward then
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2))
else
Emit(EncodeOpBx(RX_SAVE, CaptureIdx * 2 + 1));
end;
if FAltStackDepth > 0 then
Dec(FAltStackDepth);
Expand Down Expand Up @@ -2283,6 +2326,9 @@ procedure TRegExpCompiler.EmitBodyAt(const ABody: array of UInt32;
Bx: Integer;
NegFlag: Integer;
begin
if ALen <= 0 then
Exit;

EnsureCodeCapacity(ALen);
DstStart := FCodeLen;
Move(ABody[0], FCode[DstStart], ALen * SizeOf(UInt32));
Expand Down Expand Up @@ -2425,10 +2471,42 @@ procedure TRegExpCompiler.CompileTerm;
CompileQuantifier(AtomStart);
end;

// ES2026 §22.2.2.3.4 MatchSequence(m1, m2, direction)
procedure TRegExpCompiler.CompileAlternative;
var
TermStart: Integer;
TermCount: Integer;
TermIndex: Integer;
Terms: array of TRegExpTermCode;
begin
if not FBackward then
begin
while not AtEnd and (Peek <> '|') and (Peek <> ')') do
CompileTerm;
Exit;
end;

TermCount := 0;
SetLength(Terms, 8);
while not AtEnd and (Peek <> '|') and (Peek <> ')') do
begin
TermStart := CurrentPC;
CompileTerm;
if TermCount >= Length(Terms) then
SetLength(Terms, TermCount * 2 + 8);
Terms[TermCount].Length := CurrentPC - TermStart;
Terms[TermCount].OriginalStart := TermStart;
SetLength(Terms[TermCount].Code, Terms[TermCount].Length);
if Terms[TermCount].Length > 0 then
Move(FCode[TermStart], Terms[TermCount].Code[0],
Terms[TermCount].Length * SizeOf(UInt32));
FCodeLen := TermStart;
Inc(TermCount);
end;

for TermIndex := TermCount - 1 downto 0 do
EmitBodyAt(Terms[TermIndex].Code, Terms[TermIndex].Length,
Terms[TermIndex].OriginalStart);
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end;

procedure TRegExpCompiler.InsertSplitAt(APos: Integer);
Expand Down
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