Preferred string quotes

[MichaReiser]

Prettier detects the ideal quote to use for a string so that the least amount of escaped quotes are necessary:

function getPreferredQuote(rawContent, preferredQuote) {
  /** @type {{ quote: '"', regex: RegExp, escaped: """ }} */
  const double = { quote: '"', regex: /"/g, escaped: """ };
  /** @type {{ quote: "'", regex: RegExp, escaped: "'" }} */
  const single = { quote: "'", regex: /'/g, escaped: "'" };

  const preferred = preferredQuote === "'" ? single : double;
  const alternate = preferred === single ? double : single;

  let result = preferred;

  // If `rawContent` contains at least one of the quote preferred for enclosing
  // the string, we might want to enclose with the alternate quote instead, to
  // minimize the number of escaped quotes.
  if (
    rawContent.includes(preferred.quote) ||
    rawContent.includes(alternate.quote)
  ) {
    const numPreferredQuotes = (rawContent.match(preferred.regex) || []).length;
    const numAlternateQuotes = (rawContent.match(alternate.regex) || []).length;

    result = numPreferredQuotes > numAlternateQuotes ? alternate : preferred;
  }

  return result;
}

Playground

Rome should do the same when printing string literal tokens.

Input

 // Single double quote.
('"');
('"');
 
 // Single single quote.
("'");
("'");

// One of each
"\"'";
'"\'';

// One of each with unnecessary escapes.
("\"'");
("\"'");
 
 // More double quotes than single quotes.
('"\'"');
('"\'"');
 
 // More single quotes than double quotes.
("\"''");
("\"''");
 
 // Two of each.
("\"\"''");
("\"\"''");


("He's sayin': \"How's it goin'?\" Don't ask me why.");
("He's sayin': \"How's it goin'?\" Don't ask me why.");
 
 // Somewhat more real-word example 2.
('var backslash = "\\", doubleQuote = \'"\';');
('var backslash = "\\", doubleQuote = \'"\';');

Prettier

// Single double quote.
('"');
('"');

// Single single quote.
("'");
("'");

// One of each
("\"'");
("\"'");

// One of each with unnecessary escapes.
("\"'");
("\"'");

// More double quotes than single quotes.
('"\'"');
('"\'"');

// More single quotes than double quotes.
("\"''");
("\"''");

// Two of each.
("\"\"''");
("\"\"''");

("He's sayin': \"How's it goin'?\" Don't ask me why.");
("He's sayin': \"How's it goin'?\" Don't ask me why.");

// Somewhat more real-word example 2.
('var backslash = "\\", doubleQuote = \'"\';');
('var backslash = "\\", doubleQuote = \'"\';');

Rome

// Single double quote.
('"');
('"');

// Single single quote.
("'");
("'");

// One of each
"\"'";
'"\'';

// One of each with unnecessary escapes.
("\"'");
("\"'");

// More double quotes than single quotes.
('"\'"');
('"\'"');

// More single quotes than double quotes.
("\"''");
("\"''");

// Two of each.
("\"\"''");
("\"\"''");

("He's sayin': \"How's it goin'?\" Don't ask me why.");
("He's sayin': \"How's it goin'?\" Don't ask me why.");

// Somewhat more real-word example 2.
('var backslash = "\\", doubleQuote = \'"\';');
('var backslash = "\\", doubleQuote = \'"\';');

Expected

Rome's formatting to match prettier's.

[ktfth]

Learning the new code base of Rome, someone can point out a place to begin with that contribution?

[MichaReiser]

Learning the new code base of Rome, someone can point out a place to begin with that contribution?

tools/crates/rome_js_formatter/src/utils/mod.rs

Lines 614 to 637 in 77ab407

	pub(crate) fn format_string_literal_token(
	token: JsSyntaxToken,
	formatter: &Formatter,
	) -> FormatElement {
	let quoted = token.text_trimmed();
	let (primary_quote_char, secondary_quote_char) = match formatter.options().quote_style {
	QuoteStyle::Double => ('"', '\''),
	QuoteStyle::Single => ('\'', '"'),
	};
	let content =
	if quoted.starts_with(secondary_quote_char) && !quoted.contains(primary_quote_char) {
	let s = &quoted[1..quoted.len() - 1];
	let s = format!("{}{}{}", primary_quote_char, s, primary_quote_char);
	Cow::Owned(normalize_newlines(&s, ['\r']).into_owned())
	} else {
	normalize_newlines(quoted, ['\r'])
	};
	formatter.format_replaced(
	&token,
	Token::from_syntax_token_cow_slice(content, &token, token.text_trimmed_range().start())
	.into(),
	)
	}

This part is responsible for formatting string literals but currently always picks the quote-style specified in the options.

[ematipico]

I will look into this

[ematipico]

Removing the "good first issue" because it's a sensitive part of the formatter (string manipulation)