incorrect_length_validation-check: Consider check constraints with column lenght limits

lib/active_record_doctor/detectors/incorrect_length_validation.rb

@@ -33,14 +33,16 @@ def message(model:, attribute:, table:, database_maximum:, model_maximum:)
       def detect
         each_model(except: config(:ignore_models), existing_tables_only: true) do |model|
           each_attribute(model, except: config(:ignore_attributes), type: [:string, :text]) do |column|
+            table = model.table_name
             model_maximum = maximum_allowed_by_validations(model, column.name.to_sym)
-            next if model_maximum == column.limit
+            database_maximum = [column.limit, check_constraint_length_limit(table, column)].compact.min
+            next if model_maximum == database_maximum
 
             problem!(
               model: model.name,
               attribute: column.name,
-              table: model.table_name,
-              database_maximum: column.limit,
+              table: table,
+              database_maximum: database_maximum,
               model_maximum: model_maximum
             )
           end
@@ -55,6 +57,22 @@ def maximum_allowed_by_validations(model, column)
         end
         length_validator ? length_validator.options[:maximum] : nil
       end
+
+      def check_constraint_length_limit(table, column)
+        # Example: char_length(name::text) <= 64
+        pattern = /(char_|character_)?length\(['"`]?#{column.name}(::text)?['"`]?\)\s*(?<op><=?)\s*(?<limit>\d+)/i
+
+        check_constraints(table).each do |definition|
+          match = definition.match(pattern)
+          next unless match
+
+          limit = match[:limit].to_i
+          limit -= 1 if match[:op] == "<"
+          return limit
+        end
+
+        nil
+      end
     end
   end
 end

test/active_record_doctor/detectors/incorrect_length_validation_test.rb

@@ -13,9 +13,70 @@ def test_validation_and_limit_equal_is_ok
     refute_problems
   end
 
+  def test_validation_and_lteq_check_constraint_limit_equal_is_ok
+    Context.create_table(:users) do |t|
+      t.string :email
+      t.check_constraint "length(email) <= 64"
+    end.define_model do
+      validates :email, length: { maximum: 64 }
+    end
+
+    refute_problems
+  end
+
+  def test_validation_and_lt_check_constraint_limit_equal_is_ok
+    Context.create_table(:users) do |t|
+      t.string :email
+      t.check_constraint "length(email) < 65"
+    end.define_model do
+      validates :email, length: { maximum: 64 }
+    end
+
+    refute_problems
+  end
+
   def test_validation_and_limit_different_is_error
     Context.create_table(:users) do |t|
       t.string :email, limit: 64
+    end.define_model do
+      validates :email, length: { maximum: 63 }
+    end
+
+    assert_problems(<<~OUTPUT)
+      the schema limits users.email to 64 characters but the length validator on Context::User.email enforces a maximum of 63 characters - set both limits to the same value or remove both
+    OUTPUT
+  end
+
+  def test_validation_and_check_lteq_constraint_limit_different_is_error
+    Context.create_table(:users) do |t|
+      t.string :email
+      t.check_constraint "length(email) <= 33"
+    end.define_model do
+      validates :email, length: { maximum: 32 }
+    end
+
+    assert_problems(<<~OUTPUT)
+      the schema limits users.email to 33 characters but the length validator on Context::User.email enforces a maximum of 32 characters - set both limits to the same value or remove both
+    OUTPUT
+  end
+
+  def test_validation_and_check_lt_constraint_limit_different_is_error
+    Context.create_table(:users) do |t|
+      t.string :email
+      t.check_constraint "length(email) < 32"
+    end.define_model do
+      validates :email, length: { maximum: 32 }
+    end
+
+    assert_problems(<<~OUTPUT)
+      the schema limits users.email to 31 characters but the length validator on Context::User.email enforces a maximum of 32 characters - set both limits to the same value or remove both
+    OUTPUT
+  end
+
+  def test_validation_and_check_constraint_limit_and_column_limit_different_is_error
+    Context.create_table(:users) do |t|
+      t.string :email, limit: 128
+      t.check_constraint "length(email) <= 64"
     end.define_model do
       validates :email, length: { maximum: 32 }
     end
@@ -50,6 +111,18 @@ def test_no_validation_and_limit_is_error
     OUTPUT
   end
 
+  def test_no_validation_and_check_constraint_limit_is_error
+    Context.create_table(:users) do |t|
+      t.string :email
+      t.check_constraint "length(email) <= 64"
+    end.define_model do
+    end
+
+    assert_problems(<<~OUTPUT)
+      the schema limits users.email to 64 characters but there's no length validator on Context::User.email - remove the database limit or add the validator
+    OUTPUT
+  end
+
   def test_no_validation_and_no_limit_is_ok
     require_arbitrary_long_text_columns!