FrozenError when calling `.new` on STI model with state_machine in Rails 6.1

[kreintjes]

Calling .new on an ActiveRecord Single Table Inheritance model with a state_machine defined results in a "FrozenError: can't modify frozen Hash" since Rails 6.1.

Example, suppose we have the following model:

class Car < ApplicationRecord
  state_machine do
  end
end

which has a state and type column (the latter enabling STI) and some subclasses extending from Car. We would expect Car.new to return a new Car instance, but instead it crashes with "FrozenError: can't modify frozen Hash:".

Rails version: 6.1.4.1
Ruby version: 2.7.3
State machine version: 1.2.0

This did work in Rails 6.0 and before.

[slgriffiths]

I'm also hitting the "can't modify Frozen Hash" on Rails 6.1.4.4.

My annotate gem actually triggered the error and adding some tracing to the call links it back to state_machine. We also did not have this issue until we updated rails.

[t56k]

Same here from Rails 6.0.5 to 6.1.6. Any advice here?

[joshuapinter]

Seeing the same thing here. We make use of column_defaults and you can see that as of Rails 6.1, it was changed to freeze the returned Hash:

rails/rails@c9c293e

A number of Hashes were frozen in this commit. Still not sure of a workaround yet but at least we know where it came from and maybe even why.

[joshuapinter]

FYI, since this gem hasn't been updated in 10 years, we updated to the state_machines gem (notice the plural "s" there). Specifically, we used the ActiveRecord integration gem called state_machines-activerecord.

What's super nice is that it's a drop-in replacement.

We're still conducting testing but it seems to fix our issue on Rails 6.1.

[johnnyicon]

Seeing the same thing here. We make use of column_defaults and you can see that as of Rails 6.1, it was changed to freeze the returned Hash:

rails/rails@c9c293e

A number of Hashes were frozen in this commit. Still not sure of a workaround yet but at least we know where it came from and maybe even why.

Just tried this. Swapped in state_machines-activerecord. All my tests that were failing due to this issue are now passing.