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perf(es/parser): Optimize lexing of template literals #9036

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merged 3 commits into from
Jun 11, 2024
+26 −4
Merged

perf(es/parser): Optimize lexing of template literals #9036

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a6c64e6
almost
kdy1 Jun 11, 2024
7e52db7
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kdy1 Jun 11, 2024
5ac0b83
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kdy1 Jun 11, 2024
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23 changes: 17 additions & 6 deletions crates/swc_ecma_parser/src/lexer/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1160,6 +1160,7 @@ impl<'a> Lexer<'a> {

let mut cooked = Ok(String::new());
let mut raw = SmartString::new();
let mut raw_slice_start = start;

while let Some(c) = self.cur() {
if c == '`' || (c == '$' && self.peek() == Some('{')) {
Expand All @@ -1174,6 +1175,13 @@ impl<'a> Lexer<'a> {
}
}

let last_pos = self.cur_pos();
raw.push_str(unsafe {
// Safety: Both of start and last_pos are valid position because we got them
// from `self.input`
self.input.slice(raw_slice_start, last_pos)
});

// TODO: Handle error
return Ok(Token::Template {
cooked: cooked.map(Atom::from),
Expand All @@ -1182,8 +1190,14 @@ impl<'a> Lexer<'a> {
}

if c == '\\' {
raw.push('\\');
let last_pos = self.cur_pos();
raw.push_str(unsafe {
// Safety: Both of start and last_pos are valid position because we got them
// from `self.input`
self.input.slice(raw_slice_start, last_pos)
});

raw.push('\\');
let mut wrapped = Raw(Some(raw));

match self.read_escaped_char(&mut wrapped, true) {
Expand All @@ -1201,11 +1215,12 @@ impl<'a> Lexer<'a> {
}

raw = wrapped.0.unwrap();
raw_slice_start = self.cur_pos();
} else if c.is_line_terminator() {
self.state.had_line_break = true;

let c = if c == '\r' && self.peek() == Some('\n') {
raw.push('\r');
// raw.push('\r');
self.bump(); // '\r'
'\n'
} else {
Expand All @@ -1223,16 +1238,12 @@ impl<'a> Lexer<'a> {
if let Ok(ref mut cooked) = cooked {
cooked.push(c);
}

raw.push(c);
} else {
self.bump();

if let Ok(ref mut cooked) = cooked {
cooked.push(c);
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Should cooked have the same optimization?

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I think so. I'll patch it tomorrow.

}

raw.push(c);
}
}

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