Add global defaults support (#82)

* Add global defaults support

You can now set up default attributes that's applied to created/inserted records, like this:

```ruby
Oaken.prepare do
  # Assign broad global defaults for every type.
  defaults name: -> { Faker::Name.name }, public_key: -> { SecureRandom.hex }

  # Assign a more specific default on one type, which overrides the global default above.
  accounts.defaults name: -> { Faker::Business.name }
end
```

* Fix Ruby 3.0 support

README.md

@@ -64,6 +64,22 @@ Oaken has some chosen directory conventions to help strengthen your understandin
 - `db/seeds/data` for any data tables, like the plans a SaaS app has.
 - `db/seeds/tests/cases` for any specific cases that are only used in some tests, like `pagination.rb`.
 
+### Using default attributes
+
+You can set up default attributes that's applied to created/inserted records at different levels, like this:
+
+```ruby
+Oaken.prepare do
+  # Assign broad global defaults for every type.
+  defaults name: -> { Faker::Name.name }, public_key: -> { SecureRandom.hex }
+
+  # Assign a more specific default on one type, which overrides the global default above.
+  accounts.defaults name: -> { Faker::Business.name }
+end
+```
+
+[!TIP] `defaults` are particularly well suited for assigning generated data with [Faker](https://github.com/faker-ruby/faker).
+
 ### Reusing data in tests
 
 With the setup above, Oaken can reuse the same data in tests like this:

lib/oaken/seeds.rb

@@ -1,6 +1,11 @@
 module Oaken::Seeds
   extend self
 
+  # Allow assigning defaults across different types.
+  def self.defaults(**defaults) = attributes.merge!(**defaults)
+  def self.defaults_for(*keys) = attributes.slice(*keys)
+  def self.attributes = @attributes ||= {}.with_indifferent_access
+
   def self.method_missing(name, ...)
     if type = name.to_s.classify.safe_constantize
       register type

lib/oaken/stored/active_record.rb

@@ -1,7 +1,7 @@
 class Oaken::Stored::ActiveRecord
   def initialize(type)
     @type, @key = type, type.table_name
-    @attributes = {}
+    @attributes = Oaken::Seeds.defaults_for(*type.column_names)
   end
   attr_reader :type, :key
   delegate :transaction, to: :type # For multi-db setups to help open a transaction on secondary connections.

test/dummy/db/seeds.rb

@@ -1,4 +1,6 @@
 Oaken.prepare do
+  defaults name: -> { "Shouldn't be used for users.name" }, title: -> { "Global Default Title" }
+
   section :registrations
   register Menu::Item
 

test/dummy/test/models/oaken_test.rb

@@ -22,7 +22,13 @@ class OakenTest < ActiveSupport::TestCase
     assert menus.basic
   end
 
-  test "default attributes" do
+  test "global attributes" do
+    plan = plans.upsert price_cents: 10_00
+
+    assert_equal "Global Default Title", plan.reload.title
+  end
+
+  test "per-type default attributes" do
     names = users.pluck(:name)
 
     (1..10).each do