False positive for Rails/NotNullColumn when adding not null constraint to text column ?

[j-miyake]

Rails/NotNullColumn warns against adding the not null constraint to text column without the default value, however the default value can't be set for text column in MySQL. I'm not sure if this is a bug, but it made me confused. Should we fix this behavior?

C: Rails/NotNullColumn: Do not add a NOT NULL column without a default value.
    add_column :users, :bio, :text, null: false
                                    ^^^^^^^^^^^

Expected behavior

No warnings.

Actual behavior

Get a warning for Rails/NotNullColumn.

Steps to reproduce the problem

Run rubocop against to this migration code.

class AddBioToUsers < ActiveRecord::Migration[7.0]
  def change
    add_column :users, :bio, :text, null: false
  end
end

RuboCop version

$ rubocop -V
1.48.0 (using Parser 3.2.1.1, rubocop-ast 1.27.0, running on ruby 3.2.1) [aarch64-linux]
  - rubocop-performance 1.16.0
  - rubocop-rails 2.18.0
  - rubocop-rake 0.6.0
  - rubocop-rspec 2.19.0

[vlad-pisanov]

Yeah, this issue has come up before; see: #237

It's a database-specific problem. TEXT can have default values in Postgres, but not in MySQL. Since this cop doesn't know which database this migration is for, it simply always enforces a default value.

I suppose we could add a configurable "ignore list" of datatypes, but it might be easier to just disable the cop for that one line.

add_column :users, :bio, :text, null: false # rubocop:disable Rails/NotNullColumn