From 803523fb932cae1b26fd7aa81ed000f7e8656ea2 Mon Sep 17 00:00:00 2001
From: Reuben Pereira <rpereira@gitlab.com>
Date: Mon, 2 Aug 2021 11:28:37 +0530
Subject: [PATCH] Do not overwrite the database default value

When a new database record has a column that is set to its database
default value, the "#{attribute}_changed?" method returns false,
which causes default_value_for to overwrite the database default.

This commit changes this behavior to not overwrite when the column
is being set by the initialization attributes.
---
 lib/default_value_for.rb | 14 ++++++++++++++
 test.rb                  | 16 ++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/lib/default_value_for.rb b/lib/default_value_for.rb
index fc5b573..3aa6ad7 100644
--- a/lib/default_value_for.rb
+++ b/lib/default_value_for.rb
@@ -171,6 +171,20 @@ def set_default_values
                           end
         next unless connection_default_value_defined || attribute_blank
 
+        is_present = -> (value) do
+          if [true, false].include?(value)
+            !value.nil?
+          else
+            value.present?
+          end
+        end
+
+        attribute_init_value_defined = @initialization_attributes.is_a?(Hash) &&
+                                        @initialization_attributes.has_key?(attribute) &&
+                                        is_present.call(@initialization_attributes[attribute])
+
+        next if attribute_init_value_defined
+
         # allow explicitly setting nil through allow nil option
         next if @initialization_attributes.is_a?(Hash) &&
                 (
diff --git a/test.rb b/test.rb
index 361c6a3..4d73f35 100644
--- a/test.rb
+++ b/test.rb
@@ -90,6 +90,7 @@ class ToSql < (Arel::VERSION[/\A\d+/].to_i >= 6 ? Arel::Visitors::Reduce : Arel:
   t.string :type
   t.integer :number
   t.integer :count, :null => false, :default => 1
+  t.boolean :flag2, :null => false, :default => false
   t.integer :user_id
   t.timestamp :timestamp
   t.text :stuff
@@ -168,6 +169,16 @@ def test_overwrites_db_default
     assert_equal 1234, Book.new.count
   end
 
+  def test_does_not_overwrite_db_default_if_provided_by_mass_assignment
+    Book.default_value_for(:count, :allows_nil => false) { 1234 }
+    assert_equal Book.column_defaults['count'], Book.new(count: Book.column_defaults['count']).count
+  end
+
+  def test_does_not_overwrite_db_default_boolean_value_if_provided_by_mass_assignment
+    Book.default_value_for(:flag2, :allows_nil => false) { true }
+    assert_equal Book.column_defaults['flag2'], Book.new(flag2: Book.column_defaults['flag2']).flag2
+  end
+
   def test_doesnt_overwrite_values_provided_by_mass_assignment
     Book.default_value_for :number, 1234
     assert_equal 1, Book.new(:number => 1, :count => 2).number
@@ -199,6 +210,11 @@ def test_overwrites_explicitly_provided_nil_values_in_mass_assignment
     assert_equal 1234, Book.new(:number => nil).number
   end
 
+  def test_overwrites_string_blank_value_in_mass_assignment
+    Book.default_value_for(:type, :allows_nil => false) { 'string' }
+    assert_equal 'string', Book.new(type: '').type
+  end
+
   def test_default_values_are_inherited
     Book.default_value_for :number, 1234
     assert_equal 1234, Novel.new.number