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May 8, 2025
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"Improve" css selector parsing #613

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95 changes: 64 additions & 31 deletions src/browser/css/parser.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,8 @@ const PseudoClass = selector.PseudoClass;
const AttributeOP = selector.AttributeOP;
const Combinator = selector.Combinator;

const REPLACEMENT_CHARACTER = &.{ 239, 191, 189 };

pub const ParseError = error{
ExpectedSelector,
ExpectedIdentifier,
Expand Down Expand Up @@ -217,22 +219,31 @@ pub const Parser = struct {
// parseName parses a name (which is like an identifier, but doesn't have
// extra restrictions on the first character).
fn parseName(p: *Parser, w: anytype) ParseError!void {
const sel = p.s;
const sel_len = sel.len;

var i = p.i;
var ok = false;

while (i < p.s.len) {
const c = p.s[i];
while (i < sel_len) {
const c = sel[i];

if (nameChar(c)) {
const start = i;
while (i < p.s.len and nameChar(p.s[i])) i += 1;
w.writeAll(p.s[start..i]) catch return ParseError.WriteError;
while (i < sel_len and nameChar(sel[i])) i += 1;
w.writeAll(sel[start..i]) catch return ParseError.WriteError;
ok = true;
} else if (c == '\\') {
p.i = i;
try p.parseEscape(w);
i = p.i;
ok = true;
} else if (c == 0) {
w.writeAll(REPLACEMENT_CHARACTER) catch return ParseError.WriteError;
i += 1;
if (i == sel_len) {
ok = true;
}
} else {
// default:
break;
Expand All @@ -246,41 +257,60 @@ pub const Parser = struct {
// parseEscape parses a backslash escape.
// The returned string is owned by the caller.
fn parseEscape(p: *Parser, w: anytype) ParseError!void {
if (p.s.len < p.i + 2 or p.s[p.i] != '\\') {
return ParseError.InvalidEscape;
const sel = p.s;
const sel_len = sel.len;

if (sel_len < p.i + 2 or sel[p.i] != '\\') {
p.i += 1;
w.writeAll(REPLACEMENT_CHARACTER) catch return ParseError.WriteError;
return;
}

const start = p.i + 1;
const c = p.s[start];
if (ascii.isWhitespace(c)) return ParseError.EscapeLineEndingOutsideString;
const c = sel[start];

// unicode escape (hex)
if (ascii.isHex(c)) {
var i: usize = start;
while (i < start + 6 and i < p.s.len and ascii.isHex(p.s[i])) {
while (i < start + 6 and i < sel_len and ascii.isHex(sel[i])) {
i += 1;
}
const v = std.fmt.parseUnsigned(u21, p.s[start..i], 16) catch return ParseError.InvalidUnicode;
if (p.s.len > i) {
switch (p.s[i]) {
'\r' => {
i += 1;
if (p.s.len > i and p.s[i] == '\n') i += 1;
},
' ', '\t', '\n', std.ascii.control_code.ff => i += 1,
else => {},

const v = std.fmt.parseUnsigned(u21, sel[start..i], 16) catch {
p.i = i;
w.writeAll(REPLACEMENT_CHARACTER) catch return ParseError.WriteError;
return;
};

if (sel_len >= i) {
if (sel_len > i) {
switch (sel[i]) {
'\r' => {
i += 1;
if (sel_len > i and sel[i] == '\n') i += 1;
},
' ', '\t', '\n', std.ascii.control_code.ff => i += 1,
else => {},
}
}
p.i = i;
if (v == 0) {
w.writeAll(REPLACEMENT_CHARACTER) catch return ParseError.WriteError;
return;
}
var buf: [4]u8 = undefined;
const ln = std.unicode.utf8Encode(v, &buf) catch return ParseError.InvalidUnicode;
const ln = std.unicode.utf8Encode(v, &buf) catch {
w.writeAll(REPLACEMENT_CHARACTER) catch return ParseError.WriteError;
return;
};
w.writeAll(buf[0..ln]) catch return ParseError.WriteError;
return;
}
}

// Return the literal character after the backslash.
p.i += 2;
w.writeAll(p.s[start .. start + 1]) catch return ParseError.WriteError;
w.writeByte(sel[start]) catch return ParseError.WriteError;
}

// parseIDSelector parses a selector that matches by id attribute.
Expand Down Expand Up @@ -383,20 +413,23 @@ pub const Parser = struct {

// parseString parses a single- or double-quoted string.
fn parseString(p: *Parser, writer: anytype) ParseError!void {
const sel = p.s;
const sel_len = sel.len;

var i = p.i;
if (p.s.len < i + 2) return ParseError.ExpectedString;
if (sel_len < i + 2) return ParseError.ExpectedString;

const quote = p.s[i];
const quote = sel[i];
i += 1;

loop: while (i < p.s.len) {
switch (p.s[i]) {
loop: while (i < sel_len) {
switch (sel[i]) {
'\\' => {
if (p.s.len > i + 1) {
const c = p.s[i + 1];
if (sel_len > i + 1) {
const c = sel[i + 1];
switch (c) {
'\r' => {
if (p.s.len > i + 2 and p.s[i + 2] == '\n') {
if (sel_len > i + 2 and sel[i + 2] == '\n') {
i += 3;
continue :loop;
}
Expand All @@ -418,17 +451,17 @@ pub const Parser = struct {
else => |c| {
if (c == quote) break :loop;
const start = i;
while (i < p.s.len) {
const cc = p.s[i];
while (i < sel_len) {
const cc = sel[i];
if (cc == quote or cc == '\\' or c == '\r' or c == '\n' or c == std.ascii.control_code.ff) break;
i += 1;
}
writer.writeAll(p.s[start..i]) catch return ParseError.WriteError;
writer.writeAll(sel[start..i]) catch return ParseError.WriteError;
},
}
}

if (i >= p.s.len) return ParseError.InvalidString;
if (i >= sel_len) return ParseError.InvalidString;

// Consume the final quote.
i += 1;
Expand Down