Add some safeguards around calling .tenanted

Author: flavorjones

GUIDE.md

@@ -60,21 +60,23 @@ TODO:
 
 - Active Record class methods
   - [ ] `.tenanted`
-    - extends with `Base`
-    - sets `Tenant.base_class=`
-    - must only be set ONCE in the application
+    - [x] mixin `Tenant`
+    - [x] should error if self is not an abstract base class
+  - [x] `tenant_config_name` and `.tenanted?`
   - [ ] `.tenanted_with`
-    - extends with `Sublet`
-    - should error if self is not an abstract base class or if target is not tenanted abstract base class
-    - is the name right? should we have to provide the name of the tenanted class?
-  - [ ] `.tenanted?`
+    - [ ] mixin `Subtenant`
+    - [ ] should error if self is not an abstract base class or if target is not tenanted abstract base class
   - [ ] `.tenanted_class` nil or the abstract base class
   - [ ] all the creation and schema migration complications (we have existing tests for this)
     - think about race conditions here, maybe use a file lock to figure it out
       - running migrations (they are done in a transaction, but the second thread's migration may fail resulting in a 500?)
       - loading schemas (if the first thread loads the schema and inserts data, can the second thread accidentally drop/load causing data loss?)
   - [ ] feature to turn off automatic creation/migration
     - make sure we pay attention to Rails.config.active_record.migration_error when we turn off auto-migrating
+  - thinking
+    - should there be a global singleton `Tenant`? I'm not sure we need it or the limitations of a global.
+    - if we do, though, then `.tenanted` should set `Tenant.base_class=`
+    - and we need to add checks that `.tenanted` is called only ONCE in the application
 
 - database tasks
   - [ ] RootConfig should conditionally re-enable database tasks ... when AR_TENANT is present?

lib/active_record/tenanted.rb

@@ -8,6 +8,7 @@
 
 module ActiveRecord
   module Tenanted
+    class Error < StandardError; end
   end
 end
 

lib/active_record/tenanted/base.rb

@@ -13,6 +13,9 @@ def initialize(...)
         end
 
         def tenanted(config_name = "primary")
+          raise Error, "Class #{self} is already tenanted" if tenanted?
+          raise Error, "Class #{self} is not an abstract connection class" unless abstract_class?
+
           include Tenant
 
           @tenanted_config_name = config_name

test/unit/base_test.rb

@@ -20,6 +20,22 @@
       end
     end
 
+    with_scenario(:vanilla, :tenanted_primary) do
+      test "it can only be called once" do
+        e = assert_raises(ActiveRecord::Tenanted::Error) do
+          TenantedApplicationRecord.tenanted
+        end
+        assert_includes(e.message, "already tenanted")
+      end
+
+      test "it can only be called on abstract classes" do
+        e = assert_raises(ActiveRecord::Tenanted::Error) do
+          Announcement.tenanted
+        end
+        assert_includes(e.message, "not an abstract connection class")
+      end
+    end
+
     with_each_scenario do
       test "it includes the Tenant module" do
         assert_includes(TenantedApplicationRecord.ancestors, ActiveRecord::Tenanted::Tenant)