RuntimeError: can't modify frozen Array (Rollbar, Rails 5.1 upgrade)

Question

Unable to use rspec and rollbar after upgrading to rails 5.

Create a Rails 4 app
Upgrade gemfile to use rails 5
Try adding rollbar gem/support

Standard config/environment.rb:

 # Load the Rails application.
require_relative 'application'

# Initialize the Rails application.
Rails.application.initialize!

Error when running rspec:

An error occurred while loading {path to specific spec file}
Failure/Error: require File.expand_path('../../config/environment', __FILE__)

RuntimeError:
  can't modify frozen Array
# ./config/environment.rb:6:in `<top (required)>'
# ./spec/rails_helper.rb:5:in `<top (required)>'
...
No examples found.

score 29 · Accepted Answer · edited Jun 20 '20 at 09:12

29

In most cases, that error is a red herring for something else.

When encountering it, don't get overwhelmed with the recurrent can't modify frozen Array error messages, and instead check the very first error that appears when running a spec.

For example:

Failure/Error: validate :uniqueness, if: 'should_be_unique?'

ArgumentError: Passing string to be evaluated in :if and :unless conditional options is not supported. Pass a symbol for an instance method, or a lambda, proc or block, instead.

edited Jun 20 '20 at 09:12

Community

1
1

answered May 16 '18 at 13:00

Maximo Mussini

1,030
11
19

1

Thanks for posting the answer. How did you find the first error. I am seeing the same error but can't see any other errors. – DickieBoy May 07 '20 at 18:11
Thank you, you saved me likely hours of head-desk interactions. – Greg Jackson Jun 18 '20 at 21:27
Bless you. :raised_hands: – jeffdill2 Sep 29 '20 at 17:40
Thank you. Upvote for you. FWIW rspec `--fail-early` didn't show the first error. I ran `rspec > output.txt` and viewed the top of the txt file to see the first error – hummmingbear May 04 '22 at 23:20

score 6 · Answer 2 · answered May 20 '20 at 05:27

6

Just to add one tip on top of Maxximo Mussini's answer.

If anyone can't find the first error on the terminal, please try to run RSpec on one file, i.e. rspec spec/models/user_spec.rb

You should be able to find the root case.

In my case, I haven't updated my local .env variables that is required by User model

Hope it helps

answered May 20 '20 at 05:27

Andre Suchitra

143
2
8

This is helpful, but should probably be a comment on the answer you're referring to, not its own answer. – Greg Jackson Jun 18 '20 at 21:35
1

Thanks for the comment @GregJackson but I don't have 50 reputation to comment on Maximo answer. Really sorry for this – Andre Suchitra Jun 19 '20 at 10:06

Pierre-Francoys Brousseau · Answer 3 · 2020-05-16T05:09:40.073

Debugging this is not easy but one possible solution is simple. It could be a naming conflict with Rollbar, possibly something getting monkey-patched. If you're seeing this RuntimeError but not using Rollbar, see other answer.

Add a Module ("namespace" of your choice) around your app class definition in config/application.rb.

The module won't affect much. The only difference I could find is when printing out your app it will now appear as (that's how we found the fix vs a new working app):

<MyTestAPP::Application ...> instead of <Application ...>

Change:

class Application < Rails::Application
    # Initialize configuration defaults for originally generated Rails version.
    config.load_defaults 5.1
  end

To:

Module MyTestApp
  class Application < Rails::Application
    # Initialize configuration defaults for originally generated Rails version.
    config.load_defaults 5.1
  end
end

RuntimeError: can't modify frozen Array (Rollbar, Rails 5.1 upgrade)

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