Inflected table name wrong for very long model names

[martingregoire]

When having two models with very long model names, and creating a HABTM relation between them, the join table name inflected by Rails is shortened (depending on the underlying database). For PostgreSQL the table name has a maximum length of 63 characters.

For Rails this join table name is shortened automatically. For shoulda-matchers we have to explicitly define the join_table option on the relation, otherwise shoulda-matchers will report an error.

Can the inflection in shoulda-matchers include the table name length constraints used by Rails?

---

Example: these are our models:

module DataProtection
  class ProcessingActivity < ApplicationRecord
    has_and_belongs_to_many :technical_and_organisational_security_measures
  end
end

module DataProtection
  class TechnicalAndOrganisationalSecurityMeasure < ApplicationRecord
    has_and_belongs_to_many :processing_activities
  end
end

The schema.rb contains the shortened join table name for PostgreSQL:

  create_table "data_protection_processing_activities_technical_and_organisatio", force: :cascade do |t|
    t.integer "processing_activity_id", null: false
    t.integer "technical_and_organisational_security_measure_id", null: false
  end

When using these matchers in the model specs:

describe DataProtection::ProcessingActivity do
  it { should have_and_belong_to_many(:technical_and_organisational_security_measures) }
end

shoulda-matchers fails with:

Expected DataProtection::ProcessingActivity to have a has_and_belongs_to_many association called
technical_and_organisational_security_measures (join table
data_protection_processing_activities_technical_and_organisational_security_measures doesn't exist)

We tried adding the correct join table name option to the matcher:

  it { should have_and_belong_to_many(:technical_and_organisational_security_measures).join_table('data_protection_processing_activities_technical_and_organisatio') }

Now shoulda-matchers fails with:

Expected DataProtection::ProcessingActivity to have a has_and_belongs_to_many association called
technical_and_organisational_security_measures (technical_and_organisational_security_measures should use
"data_protection_processing_activities_technical_and_organisatio" for :join_table option)

This forces us to explicitly add the join_table option to the model, which is not necessary:

has_and_belongs_to_many :technical_and_organisational_security_measures, join_table: :data_protection_processing_activities_technical_and_organisatio

Now the matcher does not report an error any longer.