From 04443b2408c3f71a099afda203de0d40ff94cc0c Mon Sep 17 00:00:00 2001
From: Guo Xiang Tan <gxtan1990@gmail.com>
Date: Mon, 6 Jul 2020 17:24:05 +0800
Subject: [PATCH] Prioritize db_config for current env when resolving config.

---
 .../active_record/database_configurations.rb   | 10 ++++++----
 .../test/cases/database_configurations_test.rb | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/activerecord/lib/active_record/database_configurations.rb b/activerecord/lib/active_record/database_configurations.rb
index 2b69304788..0c4f478876 100644
--- a/activerecord/lib/active_record/database_configurations.rb
+++ b/activerecord/lib/active_record/database_configurations.rb
@@ -79,10 +79,12 @@ module ActiveRecord
     # If the application has multiple databases +find_db_config+ will return
     # the first DatabaseConfig for the environment.
     def find_db_config(env)
-      configurations.find do |db_config|
-        db_config.env_name == env.to_s ||
-          (db_config.for_current_env? && db_config.name == env.to_s)
-      end
+      configurations
+        .sort_by { |db_config| db_config.for_current_env? ? 0 : 1 }
+        .find do |db_config|
+          db_config.env_name == env.to_s ||
+            (db_config.for_current_env? && db_config.name == env.to_s)
+        end
     end
 
     # Returns the DatabaseConfigurations object as a Hash.
diff --git a/activerecord/test/cases/database_configurations_test.rb b/activerecord/test/cases/database_configurations_test.rb
index 3de9618a1f..527a18bc57 100644
--- a/activerecord/test/cases/database_configurations_test.rb
+++ b/activerecord/test/cases/database_configurations_test.rb
@@ -61,6 +61,24 @@ class DatabaseConfigurationsTest < ActiveRecord::TestCase
     assert_equal "primary", config.name
   end
 
+  def test_find_db_config_prioritize_db_config_object_for_the_current_env
+    config = ActiveRecord::DatabaseConfigurations.new({
+      "primary" => {
+        "adapter" => "randomadapter"
+      },
+      ActiveRecord::ConnectionHandling::DEFAULT_ENV.call => {
+        "primary" => {
+          "adapter" => "sqlite3",
+          "database" => ":memory:"
+        }
+      }
+    }).find_db_config("primary")
+
+    assert_equal "primary", config.name
+    assert_equal ActiveRecord::ConnectionHandling::DEFAULT_ENV.call, config.env_name
+    assert_equal ":memory:", config.database
+  end
+
   def test_to_h_turns_db_config_object_back_into_a_hash_and_is_deprecated
     configs = ActiveRecord::Base.configurations
     assert_equal "ActiveRecord::DatabaseConfigurations", configs.class.name