Prettier swallows parenthesis when doing pattern matching

[rindek]

Metadata

• Operating system: macOS Catalina

• Ruby version: 3.0.2

• Node version: v14.17.6

• @prettier/plugin-ruby or prettier gem version: @prettier/plugin-ruby@2.0.0-rc4

• Options:

  • rubyArrayLiteral - true
  • rubyHashLabel - true
  • rubyModifier - true
  • rubySingleQuote - false
  • rubyToProc - false
  • trailingComma - "all"

Input

class Test
  def compose_words(words)
    case words
    in [first, second]
      words.join(" i ")
    in [first]
      words[0]
    in [*something, second, first]
      [something.join(", "), [second, first].join(" i ")].join(", ")
    else
      ""
    end
  end
end

Current output

class Test
  def compose_words(words)
    case words
    in first, second
      words.join(" i ")
    in first
      words[0]
    in *something, second, first
      [something.join(", "), [second, first].join(" i ")].join(", ")
    else
      ""
    end
  end
end

Expected output

class Test
  def compose_words(words)
    case words
    in [first, second]
      words.join(" i ")
    in [first]
      words[0]
    in [*something, second, first]
      [something.join(", "), [second, first].join(" i ")].join(", ")
    else
      ""
    end
  end
end

Removal of square parenthesis caused the code to be bugged

[kddnewton]

Hmm looks like it creates a bug only in the [first] -> first case right?

[rindek]

No no, parenthesis must be maintained in order to properly match the array elements

Here is the tests how it should work:

  describe "#compose_words" do
    subject { compose_words(words) }

    context "no words" do
      let(:words) { [] }
      it { is_expected.to eq("") }
    end

    context "one word" do
      let(:words) { ["one"] }
      it { is_expected.to eq("one") }
    end

    context "two words" do
      let(:words) { %w[one two] }
      it { is_expected.to eq("one i two") }
    end

    context "three words" do
      let(:words) { %w[one two three] }
      it { is_expected.to eq("one, two i three") }
    end

    context "four words" do
      let(:words) { %w[one two three four] }
      it { is_expected.to eq("one, two, three i four") }
    end
  end

When parenthesis are there in every in place, then it all passes, if there is no parenthesis anywhere, it passes only two words example - for matching an array elements, [] must be there, as it is not case when but case in

[kddnewton]

Doesn't this pass your tests?

class Test
  def compose_words(words)
    case words
    in first, second
      words.join(" i ")
    in [first]
      words[0]
    in *something, second, first
      [something.join(", "), [second, first].join(" i ")].join(", ")
    else
      ""
    end
  end
end

[rindek]

Oh right, it does!

[rindek]

TIL, I actually did not know that you can omit the parenthesis to properly match multiple array elems
But yes, it match only having one elem when prettier replaces [first] -> first it breaks

[rindek]

Wow, that was fast! Big thanks @kddnewton :)