Merge pull request rails#46605 from ghiculescu/compute_class_error

More detailed error message for `compute_class` errors

Author: rafaelfranca

activerecord/lib/active_record/reflection.rb

@@ -423,22 +423,16 @@ def compute_class(name)
           raise ArgumentError, "Polymorphic associations do not support computing the class."
         end
 
-        msg = <<-MSG.squish
-          Rails couldn't find a valid model for #{name} association.
-          Please provide the :class_name option on the association declaration.
-          If :class_name is already provided, make sure it's an ActiveRecord::Base subclass.
-        MSG
-
         begin
           klass = active_record.send(:compute_type, name)
 
           unless klass < ActiveRecord::Base
-            raise ArgumentError, msg
+            raise ArgumentError, compute_class_error_message(klass)
           end
 
           klass
         rescue NameError
-          raise NameError, msg
+          raise ArgumentError, compute_class_error_message
         end
       end
 
@@ -605,6 +599,16 @@ def extensions
       end
 
       private
+        def compute_class_error_message(klass = nil)
+          msg = +"Rails couldn't find a valid model for the #{name} association. "
+          if !options[:class_name]
+            msg << "Use the :class_name option on the association declaration to tell Rails which model to use."
+          else
+            msg << "Ensure the class provided to :class_name exists and is an ActiveRecord::Base subclass."
+          end
+          msg
+        end
+
         # Attempts to find the inverse association name automatically.
         # If it cannot find a suitable inverse association name, it returns
         # +nil+.

activerecord/test/cases/associations_test.rb

@@ -417,15 +417,15 @@ class ModelAssociatedToClassesThatDoNotExist < ActiveRecord::Base
   end
 
   def test_associations_raise_with_name_error_if_associated_to_classes_that_do_not_exist
-    assert_raises NameError do
+    assert_raises ArgumentError do
       ModelAssociatedToClassesThatDoNotExist.new.non_existent_has_one_class
     end
 
-    assert_raises NameError do
+    assert_raises ArgumentError do
       ModelAssociatedToClassesThatDoNotExist.new.non_existent_belongs_to_class
     end
 
-    assert_raises NameError do
+    assert_raises ArgumentError do
       ModelAssociatedToClassesThatDoNotExist.new.non_existent_has_many_classes
     end
   end

activerecord/test/cases/reflection_test.rb

@@ -138,16 +138,51 @@ def test_irregular_reflection_class_name
     assert_equal "PluralIrregular", reflection.class_name
   end
 
-  def test_reflection_klass_is_not_ar_subclass
-    [:account_invalid,
-     :account_class_name,
+  def test_reflection_klass_not_found_with_no_class_name_option
+    [:account_invalid_no_class_name_option,
      :info_invalids,
+    ].each do |rel|
+      expected = <<-MSG.squish
+        Rails couldn't find a valid model for the #{rel} association.
+        Use the :class_name option on the association declaration to tell Rails which model to use.
+      MSG
+
+      err = assert_raise(ArgumentError) do
+        UserWithInvalidRelation.reflect_on_association(rel).klass
+      end
+
+      assert_includes err.message, expected
+    end
+  end
+
+  def test_reflection_klass_not_found_with_pointer_to_non_existent_class_name
+    expected = <<-MSG.squish
+      Rails couldn't find a valid model for the class_name_provided_not_a_class association.
+      Ensure the class provided to :class_name exists and is an ActiveRecord::Base subclass.
+    MSG
+
+    err = assert_raise(ArgumentError) do
+      UserWithInvalidRelation.reflect_on_association(:class_name_provided_not_a_class).klass
+    end
+
+    assert_includes err.message, expected
+  end
+
+  def test_reflection_klass_requires_ar_subclass
+    [:account_class_name,
      :infos_class_name,
      :infos_through_class_name,
     ].each do |rel|
-      assert_raise(ArgumentError) do
+      expected = <<-MSG.squish
+        Rails couldn't find a valid model for the #{rel} association.
+        Ensure the class provided to :class_name exists and is an ActiveRecord::Base subclass.
+      MSG
+
+      err = assert_raise(ArgumentError) do
         UserWithInvalidRelation.reflect_on_association(rel).klass
       end
+
+      assert_includes err.message, expected
     end
   end
 

activerecord/test/models/user_with_invalid_relation.rb

@@ -1,10 +1,12 @@
 # frozen_string_literal: true
 
 class UserWithInvalidRelation < ActiveRecord::Base
-  has_one :account_invalid
+  has_one :account_invalid_no_class_name_option
 
   has_one :account_class_name, class_name: "AccountInvalid"
 
+  has_one :class_name_provided_not_a_class, class_name: "NotAClass"
+
   has_many :user_info_invalid
   has_many :info_invalids, through: :user_info_invalid