test.rb

require "active_record"
require "logger"

puts ActiveRecord::VERSION::STRING

# ActiveRecord::Base.logger = Logger.new(STDERR)
ActiveRecord::Base.establish_connection adapter: 'sqlite3', database: ':memory:'

ActiveRecord::Schema.define do
  create_table :people

  connection.create_table :accesses do |t|
    t.integer :person_id
    t.integer :project_id
  end

  connection.create_table :projects do |t|
    t.boolean :trashed
  end
end

class Person < ActiveRecord::Base
  has_many :accesses
  has_many :projects, -> { where trashed: false }, through: :accesses
  # has_many :projects, conditions: { trashed: false }, through: :accesses # <-- uncomment for 3.2
end

class Access < ActiveRecord::Base
  belongs_to :person
  belongs_to :project, -> { where trashed: [ true, false ] }
  # belongs_to :project, conditions: { trashed: [ true, false ] } # <-- uncomment for 3.2
end

class Project < ActiveRecord::Base
end

person = Person.create
puts person.projects.to_sql