stack level too deep

Dockerfile

FROM alpine:3.7

# skip installing gem documentation
RUN mkdir -p /usr/local/etc \
	&& { \
		echo 'install: --no-document'; \
		echo 'update: --no-document'; \
	} >> /usr/local/etc/gemrc

ENV RUBY_MAJOR 2.5
ENV RUBY_VERSION 2.5.0
ENV RUBY_DOWNLOAD_SHA256 1da0afed833a0dab94075221a615c14487b05d0c407f991c8080d576d985b49b
ENV RUBYGEMS_VERSION 2.7.4
ENV BUNDLER_VERSION 1.16.1

# some of ruby's build scripts are written in ruby
#   we purge system ruby later to make sure our final image uses what we just built
# readline-dev vs libedit-dev: https://bugs.ruby-lang.org/issues/11869 and https://github.com/docker-library/ruby/issues/75
RUN set -ex \
	\
	&& apk add --no-cache --virtual .ruby-builddeps \
		autoconf \
		bison \
		bzip2 \
		bzip2-dev \
		ca-certificates \
		coreutils \
		dpkg-dev dpkg \
		gcc \
		gdbm-dev \
		glib-dev \
		libc-dev \
		libffi-dev \
		libressl \
		libressl-dev \
		libxml2-dev \
		libxslt-dev \
		linux-headers \
		make \
		ncurses-dev \
		procps \
		readline-dev \
		ruby \
		tar \
		xz \
		yaml-dev \
		zlib-dev \
                git \
	\
	&& git clone https://github.com/ruby/ruby.git \
	&& cd ruby \
	\
# hack in "ENABLE_PATH_CHECK" disabling to suppress:
#   warning: Insecure world writable dir
	&& { \
		echo '#define ENABLE_PATH_CHECK 0'; \
		echo; \
		cat file.c; \
	} > file.c.new \
	&& mv file.c.new file.c \
	\
	&& autoconf \
	&& gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)" \
# the configure script does not detect isnan/isinf as macros
	&& export ac_cv_func_isnan=yes ac_cv_func_isinf=yes \
	&& ./configure \
		--build="$gnuArch" \
		--disable-install-doc \
		--enable-shared \
	&& make -j "$(nproc)" \
	&& make install \
	\
	&& runDeps="$( \
		scanelf --needed --nobanner --format '%n#p' --recursive /usr/local \
			| tr ',' '\n' \
			| sort -u \
			| awk 'system("[ -e /usr/local/lib/" $1 " ]") == 0 { next } { print "so:" $1 }' \
	)" \
	&& apk add --virtual .ruby-rundeps $runDeps \
		bzip2 \
		ca-certificates \
		libffi-dev \
		libressl-dev \
		procps \
		yaml-dev \
		zlib-dev \
	&& apk del .ruby-builddeps \
	&& cd / \
	&& gem update --system "$RUBYGEMS_VERSION" \
	&& gem install bundler --version "$BUNDLER_VERSION" --force

# install things globally, for great justice
# and don't create ".bundle" in all our apps
ENV GEM_HOME /usr/local/bundle
ENV BUNDLE_PATH="$GEM_HOME" \
	BUNDLE_BIN="$GEM_HOME/bin" \
	BUNDLE_SILENCE_ROOT_WARNING=1 \
	BUNDLE_APP_CONFIG="$GEM_HOME"
ENV PATH $BUNDLE_BIN:$PATH
RUN mkdir -p "$GEM_HOME" "$BUNDLE_BIN" \
	&& chmod 777 "$GEM_HOME" "$BUNDLE_BIN"

CMD [ "irb" ]

sample.rb

require 'rails_helper'

RSpec.describe MyClass do
  describe '#my_method' do
    subject { MyClass.new.my_method(arg) }

    context 'when ...' do
      context 'when ...' do
        context 'when ...' do
          context 'when ...' do
            let(:arg) { create(:arg, :trait, attr: x) }

            it 'should be ...' do
              YourClass.new(
                x: X.x(
                  y: Y.y(
                    z: Z.z(
                      a: A.a(
                        b: B.b
                      )
                    )
                  )
                )
              )
            end
          end
        end
      end
    end
  end
end

step.txt

[docker-for-mac]% docker build -t ruby:trunk-alpine3.7 -f Dockerfile .
[docker-for-mac]% docker container run --rm -it ruby:trunk-alpine3.7 sh

/# gem install rubocop
/ # rubocop sample.rb
Inspecting 1 file


0 files inspected, no offenses detected
Traceback (most recent call last):
        142: from /usr/local/bundle/bin/rubocop:23:in `<main>'
        141: from /usr/local/bundle/bin/rubocop:23:in `load'
        140: from /usr/local/bundle/gems/rubocop-0.52.1/bin/rubocop:12:in `<top (required)>'
        139: from /usr/local/lib/ruby/2.6.0/benchmark.rb:308:in `realtime'
        138: from /usr/local/bundle/gems/rubocop-0.52.1/bin/rubocop:13:in `block in <top (required)>'
        137: from /usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/cli.rb:38:in `run'
        136: from /usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/cli.rb:78:in `execute_runners'
        135: from /usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/cli.rb:150:in `execute_runner'
         ... 130 levels...
          4: from /usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/ast/node.rb:172:in `each'
          3: from /usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/ast/node.rb:174:in `block in each_child_node'
          2: from /usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/ast/node.rb:87:in `complete!'
          1: from /usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/ast/node.rb:172:in `each_child_node'
/usr/local/bundle/gems/rubocop-0.52.1/lib/rubocop/ast/node.rb:172:in `each': stack level too deep (SystemStackError)