@prettier/plugin-ruby/src/nodes/regexp.js

prettier plugin for the Ruby programming language

const { concat } = require("../prettier");
const { hasAncestor } = require("../utils");

function isStringContent(node) {
  return node.type === "@tstring_content";
}

function shouldUseBraces(path) {
  const node = path.getValue();
  const first = node.body[0];

  // If the first part of this regex is plain string content and we have a
  // space or an =, then we want to use braces because otherwise we could end up
  // with an ambiguous operator, e.g. foo / bar/ or foo /=bar/
  if (
    first &&
    isStringContent(first) &&
    [" ", "="].includes(first.body[0]) &&
    hasAncestor(path, ["command", "command_call"])
  ) {
    return true;
  }

  return node.body.some(
    (child) => isStringContent(child) && child.body.includes("/")
  );
}

// This function is responsible for printing out regexp_literal nodes. They can
// either use the special %r literal syntax or they can use forward slashes. At
// the end of either of those they can have modifiers like m or x that have
// special meaning for the regex engine.
//
// We favor the use of forward slashes unless the regex contains a forward slash
// itself. In that case we switch over to using %r with braces.
function printRegexpLiteral(path, opts, print) {
  const node = path.getValue();
  const useBraces = shouldUseBraces(path);

  const parts = [useBraces ? "%r{" : "/"]
    .concat(path.map(print, "body"))
    .concat([useBraces ? "}" : "/", node.ending.slice(1)]);

  return concat(parts);
}

module.exports = {
  regexp_literal: printRegexpLiteral
};