Rails/RelativeDateConstant errors on constants defined with conditional assignment operator

[timrogers]

Constants defined with a conditional assignment operator (we do this to prevent specs from trying to redefine constants if a file is required more than once) caused the Rails/RelativeDateConstant cop to error.

Expected behavior

The cop should allow code like the following, because it doesn't contain a relative date:

DEFAULT_SUBJECT ||= "My Default Subject"

Actual behavior

Rubocop errors like this:

ndefined method `lambda_or_proc?' for nil:NilClass
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/rails/relative_date_constant.rb:30:in `on_casgn'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:43:in `block (2 levels) in on_casgn'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:106:in `with_cop_error_handling'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:42:in `block in on_casgn'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:41:in `each'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:41:in `on_casgn'
(eval):2:in `block in on_or_asgn'
(eval):2:in `each'
(eval):2:in `on_or_asgn'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:47:in `on_or_asgn'
(eval):2:in `block in on_begin'
(eval):2:in `each'
(eval):2:in `on_begin'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:47:in `on_begin'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/ast/traversal.rb:88:in `on_class'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:47:in `on_class'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/ast/traversal.rb:141:in `on_while'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:47:in `on_module'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/ast/traversal.rb:12:in `walk'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/commissioner.rb:60:in `investigate'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/team.rb:124:in `investigate'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/team.rb:112:in `offenses'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cop/team.rb:54:in `inspect_file'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:248:in `inspect_file'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:195:in `block in do_inspection_loop'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:227:in `block in iterate_until_no_changes'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:220:in `loop'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:220:in `iterate_until_no_changes'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:191:in `do_inspection_loop'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:101:in `block in file_offenses'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:111:in `file_offense_cache'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:99:in `file_offenses'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:90:in `process_file'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:68:in `block in each_inspected_file'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:65:in `each'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:65:in `reduce'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:65:in `each_inspected_file'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:57:in `inspect_files'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/runner.rb:36:in `run'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cli.rb:72:in `execute_runner'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/lib/rubocop/cli.rb:27:in `run'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/bin/rubocop:13:in `block in <top (required)>'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/2.3.0/benchmark.rb:308:in `realtime'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/rubocop-0.48.1/bin/rubocop:12:in `<top (required)>'
/Users/timrogers/.rbenv/versions/2.3.3/bin/rubocop:22:in `load'
/Users/timrogers/.rbenv/versions/2.3.3/bin/rubocop:22:in `<top (required)>'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/cli/exec.rb:74:in `load'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/cli/exec.rb:74:in `kernel_load'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/cli/exec.rb:27:in `run'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/cli.rb:335:in `exec'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in `invoke_command'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/vendor/thor/lib/thor.rb:359:in `dispatch'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/cli.rb:20:in `dispatch'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/vendor/thor/lib/thor/base.rb:440:in `start'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/cli.rb:11:in `start'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/exe/bundle:32:in `block in <top (required)>'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/lib/bundler/friendly_errors.rb:121:in `with_friendly_errors'
/Users/timrogers/.rbenv/versions/2.3.3/lib/ruby/gems/2.3.0/gems/bundler-1.14.6/exe/bundle:24:in `<top (required)>'
/Users/timrogers/.rbenv/versions/2.3.3/bin/bundle:22:in `load'
/Users/timrogers/.rbenv/versions/2.3.3/bin/bundle:22:in `<main>'

Steps to reproduce the problem

Use the conditional assignment operator (||=) to define a constant

RuboCop version

$ bundle exec rubocop -V
0.48.1 (using Parser 2.4.0.0, running on ruby 2.3.3 x86_64-darwin16)

[timrogers]

@bbatsov Thanks ❤️ (I wasn't planning a drive-by issue and was going to look at fixing this myself, but am very thankful that you got a chance before me!)

[bbatsov]

Well, it turned out this cop wasn't even supporting ||=. :-) Thought the problem was a missing nil check, turned out it it was more complex, but it was fun to fix it.