From 0401f50d645b8cb30c1221099141393a5d570422 Mon Sep 17 00:00:00 2001
From: Hartley McGuire <skipkayhil@gmail.com>
Date: Sat, 18 Feb 2023 17:28:22 -0500
Subject: [PATCH] Allow 3-tier shared config in database.yml

Previously, the shared config hash would be merged with all database
configurations defined in database.yml.

This commit makes the shared hash 3-tier aware so that it can be used
to share configuration across environments but only with matching
configuration names.

For example:

```yaml
shared:
  one:
    migrations_path: "db/one"
  two:
    migrations_path: "db/two"

development:
  one:
    adapter: sqlite3
  two:
    adapter: sqlite3

production:
  one:
    adapter: mysql2
  two:
    adapter: mysql2
```

Will now properly set the migration_path for the one and two
configurations in both development and production.
---
 .../lib/rails/application/configuration.rb    | 10 +++++++--
 .../test/application/configuration_test.rb    | 22 +++++++++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index b7d458ae8753f..d8603ff78709c 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -417,8 +417,14 @@ def database_configuration
           if (shared = loaded_yaml.delete("shared"))
             loaded_yaml.each do |env, config|
               if config.is_a?(Hash) && config.values.all?(Hash)
-                config.map do |name, sub_config|
-                  sub_config.reverse_merge!(shared)
+                if shared.is_a?(Hash) && shared.values.all?(Hash)
+                  config.map do |name, sub_config|
+                    sub_config.reverse_merge!(shared[name])
+                  end
+                else
+                  config.map do |name, sub_config|
+                    sub_config.reverse_merge!(shared)
+                  end
                 end
               else
                 config.reverse_merge!(shared)
diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index d988b9c0233cb..d8cf199f58b49 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -2180,6 +2180,28 @@ def index
       assert_equal "dev_db",  ar_config["development"]["primary"]["database"]
     end
 
+    test "loads database.yml using 3-tier shared keys with a 3-tier config" do
+      app_file "config/database.yml", <<-YAML
+        shared:
+          one:
+            migrations_path: "db/one"
+          two:
+            migrations_path: "db/two"
+
+        development:
+          one:
+            adapter: sqlite3
+          two:
+            adapter: sqlite3
+      YAML
+
+      app "development"
+
+      ar_config = Rails.configuration.database_configuration
+      assert_equal "db/one", ar_config["development"]["one"]["migrations_path"]
+      assert_equal "db/two", ar_config["development"]["two"]["migrations_path"]
+    end
+
     test "config.action_mailer.show_previews defaults to true in development" do
       app "development"