Add support for models which use non-primary key columns for lookup (i.e. external_id columns)

lib/global_id/identification.rb

@@ -1,3 +1,5 @@
+require "active_support/core_ext/class/attribute"
+
 class GlobalID
   # Mix `GlobalID::Identification` into any model with a `#find(id)` class
   # method. Support is automatically included in Active Record.
@@ -26,6 +28,9 @@ class GlobalID
   #   GlobalID::Locator.locate person_gid
   #   # => #<Person:0x007fae94bf6298 @id="1">
   module Identification
+    def self.included(base)
+      base.class_attribute :global_id_column, default: :id, instance_writer: false
+    end
 
     # Returns the Global ID of the model.
     #

lib/global_id/locator.rb

@@ -162,7 +162,11 @@ def locate(gid, options = {})
           model_class = gid.model_class
           model_class = model_class.includes(options[:includes]) if options[:includes]
 
-          model_class.find gid.model_id
+          if model_class.global_id_column == :id
+            model_class.find gid.model_id
+          else
+            model_class.find_by model_class.global_id_column => gid.model_id
+          end
         end
 
         def locate_many(gids, options = {})

lib/global_id/uri/gid.rb

@@ -72,7 +72,7 @@ def parse(uri)
       #
       #   URI::GID.create('bcx', Person.find(5), database: 'superhumans')
       def create(app, model, params = nil)
-        build app: app, model_name: model.class.name, model_id: model.id, params: params
+        build app: app, model_name: model.class.name, model_id: model.public_send(model.global_id_column), params: params
       end
 
       # Create a new URI::GID from components with argument check.

test/cases/global_id_test.rb

@@ -45,6 +45,8 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     @person_namespaced_gid = GlobalID.create(Person::Child.new(4))
     @person_model_gid = GlobalID.create(PersonModel.new(id: 1))
     @cpk_model_gid = GlobalID.create(CompositePrimaryKeyModel.new(id: ["tenant-key-value", "id-value"]))
+    @ckm_model = ConfigurableKeyModel.new(id: "id-value", external_id: "external-id-value")
+    @ckm_model_gid = GlobalID.create(@ckm_model)
   end
 
   test 'find' do
@@ -53,13 +55,15 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     assert_equal Person::Child.find(@person_namespaced_gid.model_id), @person_namespaced_gid.find
     assert_equal PersonModel.find(@person_model_gid.model_id), @person_model_gid.find
     assert_equal CompositePrimaryKeyModel.find(@cpk_model_gid.model_id), @cpk_model_gid.find
+    assert_equal ConfigurableKeyModel.find_by(external_id: @ckm_model_gid.model_id), @ckm_model_gid.find
   end
 
   test 'find with class' do
     assert_equal Person.find(@person_gid.model_id), @person_gid.find(only: Person)
     assert_equal Person.find(@person_uuid_gid.model_id), @person_uuid_gid.find(only: Person)
     assert_equal PersonModel.find(@person_model_gid.model_id), @person_model_gid.find(only: PersonModel)
     assert_equal CompositePrimaryKeyModel.find(@cpk_model_gid.model_id), @cpk_model_gid.find(only: CompositePrimaryKeyModel)
+    assert_equal ConfigurableKeyModel.find_by(external_id: @ckm_model_gid.model_id), @ckm_model_gid.find(only: ConfigurableKeyModel)
   end
 
   test 'find with class no match' do
@@ -68,6 +72,7 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     assert_nil @person_namespaced_gid.find(only: String)
     assert_nil @person_model_gid.find(only: Float)
     assert_nil @cpk_model_gid.find(only: Hash)
+    assert_nil @ckm_model_gid.find(only: Hash)
   end
 
   test 'find with subclass' do
@@ -140,6 +145,7 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     assert_equal 'gid://bcx/Person::Child/4', @person_namespaced_gid.to_s
     assert_equal 'gid://bcx/PersonModel/1', @person_model_gid.to_s
     assert_equal 'gid://bcx/CompositePrimaryKeyModel/tenant-key-value/id-value', @cpk_model_gid.to_s
+    assert_equal 'gid://bcx/ConfigurableKeyModel/external-id-value', @ckm_model_gid.to_s
   end
 
   test 'as param' do
@@ -166,6 +172,7 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     assert_equal URI('gid://bcx/Person::Child/4'), @person_namespaced_gid.uri
     assert_equal URI('gid://bcx/PersonModel/1'), @person_model_gid.uri
     assert_equal URI('gid://bcx/CompositePrimaryKeyModel/tenant-key-value/id-value'), @cpk_model_gid.uri
+    assert_equal URI('gid://bcx/ConfigurableKeyModel/external-id-value'), @ckm_model_gid.uri
   end
 
   test 'as JSON' do
@@ -183,6 +190,9 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
 
     assert_equal 'gid://bcx/CompositePrimaryKeyModel/tenant-key-value/id-value', @cpk_model_gid.as_json
     assert_equal '"gid://bcx/CompositePrimaryKeyModel/tenant-key-value/id-value"', @cpk_model_gid.to_json
+
+    assert_equal 'gid://bcx/ConfigurableKeyModel/external-id-value', @ckm_model_gid.as_json
+    assert_equal '"gid://bcx/ConfigurableKeyModel/external-id-value"', @ckm_model_gid.to_json
   end
 
   test 'model id' do
@@ -191,6 +201,7 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     assert_equal '4', @person_namespaced_gid.model_id
     assert_equal '1', @person_model_gid.model_id
     assert_equal ['tenant-key-value', 'id-value'], @cpk_model_gid.model_id
+    assert_equal 'external-id-value', @ckm_model_gid.model_id
   end
 
   test 'model name' do
@@ -199,6 +210,7 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     assert_equal 'Person::Child', @person_namespaced_gid.model_name
     assert_equal 'PersonModel', @person_model_gid.model_name
     assert_equal 'CompositePrimaryKeyModel', @cpk_model_gid.model_name
+    assert_equal 'ConfigurableKeyModel', @ckm_model_gid.model_name
   end
 
   test 'model class' do
@@ -207,6 +219,7 @@ class GlobalIDCreationTest < ActiveSupport::TestCase
     assert_equal Person::Child, @person_namespaced_gid.model_class
     assert_equal PersonModel, @person_model_gid.model_class
     assert_equal CompositePrimaryKeyModel, @cpk_model_gid.model_class
+    assert_equal ConfigurableKeyModel, @ckm_model_gid.model_class
     assert_raise ArgumentError do
       GlobalID.find 'gid://bcx/SignedGlobalID/5'
     end

test/cases/uri_gid_test.rb

@@ -6,13 +6,18 @@ class URI::GIDTest <  ActiveSupport::TestCase
     @gid = URI::GID.parse(@gid_string)
     @cpk_gid_string = 'gid://bcx/CompositePrimaryKeyModel/tenant-key-value/id-value'
     @cpk_gid = URI::GID.parse(@cpk_gid_string)
+    @ckm_gid_string = 'gid://bcx/ConfigurableKeyModel/external-id-123'
+    @ckm_gid = URI::GID.parse(@ckm_gid_string)
   end
 
   test 'parsed' do
     assert_equal @gid.app, 'bcx'
     assert_equal @gid.model_name, 'Person'
     assert_equal @gid.model_id, '5'
     assert_equal ["tenant-key-value", "id-value"], @cpk_gid.model_id
+    assert_equal @ckm_gid.app, 'bcx'
+    assert_equal @ckm_gid.model_name, 'ConfigurableKeyModel'
+    assert_equal @ckm_gid.model_id, 'external-id-123'
   end
 
   test 'parsed for non existing model class' do
@@ -39,6 +44,11 @@ class URI::GIDTest <  ActiveSupport::TestCase
     assert_equal @cpk_gid_string, URI::GID.create('bcx', model).to_s
   end
 
+  test 'create from a configurable key model' do
+    model = ConfigurableKeyModel.new(id: 'id-value', external_id: 'external-id-123')
+    assert_equal @ckm_gid_string, URI::GID.create('bcx', model).to_s
+  end
+
   test 'build' do
     array = URI::GID.build(['bcx', 'Person', '5', nil])
     assert array
@@ -65,6 +75,21 @@ class URI::GIDTest <  ActiveSupport::TestCase
     assert_equal("gid://bcx/CompositePrimaryKeyModel/tenant-key-value/id-value", array.to_s)
   end
 
+  # NOTE: I'm not sure if this test is valuable, it's pretty duplicative with the standard
+  #   test path, but with a different value passed in for `model_id:`
+  test 'build with a configurable key model' do
+    array = URI::GID.build(['bcx', 'ConfigurableKeyModel', 'external-id-123', nil])
+    gid = URI::GID.build(
+      app: 'bcx',
+      model_name: 'ConfigurableKeyModel',
+      model_id: 'external-id-123',
+      params: nil
+    )
+
+    assert_equal array, gid
+    assert_equal 'gid://bcx/ConfigurableKeyModel/external-id-123', array.to_s
+  end
+
   test 'build with wrong ordered array creates a wrong ordered gid' do
     assert_not_equal @gid_string, URI::GID.build(['Person', '5', 'bcx', nil]).to_s
   end

test/helper.rb

@@ -8,6 +8,7 @@
 require 'models/person'
 require 'models/person_model'
 require 'models/composite_primary_key_model'
+require 'models/configurable_key_model'
 
 require 'json'
 

test/models/configurable_key_model.rb

@@ -0,0 +1,28 @@
+require 'active_model'
+
+class ConfigurableKeyModel
+  include ActiveModel::Model
+  include GlobalID::Identification
+
+  attr_accessor :id, :external_id
+
+  self.global_id_column = :external_id
+
+  class << self
+    def primary_key
+      :id
+    end
+
+    def find(_id)
+      raise ".find is not supported for ConfigurableKeyModel"
+    end
+
+    def find_by(external_id:)
+      new external_id: external_id, id: "id-value"
+    end
+  end
+
+  def ==(other)
+    external_id == other.try(:external_id)
+  end
+end