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

prettier plugin for the Ruby programming language

const {
  align,
  breakParent,
  concat,
  group,
  hardline,
  ifBreak,
  indent,
  softline
} = require("../prettier");

const { containsAssignment } = require("../utils");
const inlineEnsureParens = require("../utils/inlineEnsureParens");

const printLoop = (keyword, modifier) => (path, { rubyModifier }, print) => {
  const [_predicate, stmts] = path.getValue().body;

  // If the only statement inside this while loop is a void statement, then we
  // can shorten to just displaying the predicate and then a semicolon.
  if (
    stmts.body.length === 1 &&
    stmts.body[0].type === "void_stmt" &&
    !stmts.body[0].comments
  ) {
    return group(
      concat([
        keyword,
        " ",
        path.call(print, "body", 0),
        ifBreak(softline, "; "),
        "end"
      ])
    );
  }

  const inlineLoop = concat(
    inlineEnsureParens(path, [
      path.call(print, "body", 1),
      ` ${keyword} `,
      path.call(print, "body", 0)
    ])
  );

  // If we're in the modifier form and we're modifying a `begin`, then this is a
  // special case where we need to explicitly use the modifier form because
  // otherwise the semantic meaning changes. This looks like:
  //
  //     begin
  //       foo
  //     end while bar
  //
  // The above is effectively a `do...while` loop (which we don't have in ruby).
  if (modifier && path.getValue().body[1].type === "begin") {
    return inlineLoop;
  }

  const blockLoop = concat([
    concat([
      `${keyword} `,
      align(keyword.length + 1, path.call(print, "body", 0))
    ]),
    indent(concat([softline, path.call(print, "body", 1)])),
    concat([softline, "end"])
  ]);

  // If we're disallowing inline loops or if the predicate of the loop contains
  // an assignment (in which case we can't know for certain that that
  // assignment doesn't impact the statements inside the loop) then we can't
  // use the modifier form and we must use the block form.
  if (!rubyModifier || containsAssignment(path.getValue().body[0])) {
    return concat([breakParent, blockLoop]);
  }

  return group(ifBreak(blockLoop, inlineLoop));
};

// Technically this is incorrect. A `for` loop actually introduces and modifies
// a local variable that then remains in the outer scope. Additionally, if the
// `each` method was somehow missing from the enumerable (it's possible...),
// then this transformation would fail. However - I've never actually seen a
// `for` loop used in production. If someone actually calls me on it, I'll fix
// this, but for now I'm leaving it.
const printFor = (path, opts, print) =>
  group(
    concat([
      path.call(print, "body", 1),
      ".each do |",
      path.call(print, "body", 0),
      "|",
      indent(concat([hardline, path.call(print, "body", 2)])),
      concat([hardline, "end"])
    ])
  );

module.exports = {
  while: printLoop("while", false),
  while_mod: printLoop("while", true),
  until: printLoop("until", false),
  until_mod: printLoop("until", true),
  for: printFor
};