From 02de62d2c80ede2716275406f96e4727fbebae10 Mon Sep 17 00:00:00 2001
From: Sam Ruby <rubys@intertwingly.net>
Date: Tue, 24 Sep 2024 15:16:06 -0400
Subject: [PATCH] Enable DATABASE_URL to control the placement of all of the
 databases

See: https://discuss.rubyonrails.org/t/brainstorming-approaches-to-reconcile-rails-8s-default-multi-db-setup-with-database-url/86769
---
 lib/generators/dockerfile_generator.rb    |  29 ++++++
 lib/generators/templates/database.yml.erb |   1 +
 test/base.rb                              |  10 +++
 test/results/postgresql/Dockerfile        |   4 +-
 test/results/postgresql/database.yml      | 102 ++++++++++++++++++++++
 test/test_postgres.rb                     |   3 +-
 6 files changed, 146 insertions(+), 3 deletions(-)
 create mode 100644 lib/generators/templates/database.yml.erb
 create mode 100644 test/results/postgresql/database.yml

diff --git a/lib/generators/dockerfile_generator.rb b/lib/generators/dockerfile_generator.rb
index 50249c6..5e0a924 100644
--- a/lib/generators/dockerfile_generator.rb
+++ b/lib/generators/dockerfile_generator.rb
@@ -331,6 +331,8 @@ def generate_app
 
     template "docker-compose.yml.erb", "docker-compose.yml" if options.compose
 
+    template "database.yml.erb", "config/database.yml" if fix_database_config
+
     if using_litefs?
       template "litefs.yml.erb", "config/litefs.yml"
 
@@ -1450,4 +1452,31 @@ def fly_make_toml
 
     toml
   end
+
+  # if there are multiple production databases defined, allow them all to be
+  # configured via DATABASE_URL.
+  def fix_database_config
+    yaml = IO.read("config/database.yml")
+
+    production = YAML.load(yaml, aliases: true)["production"]
+    return unless production.is_a?(Hash) && production.values.all?(Hash)
+    return if production.keys == [ "primary" ]
+
+    section = yaml[/^(production:.*?)(^\S|\z)/m, 1]
+
+    replacement = section.gsub(/(  ).*?\n((\1\s+).*?\n)*/) do |subsection|
+      spaces = $3
+      name = subsection[/\w+/]
+
+      if /^ +url:/.match?(subsection)
+        subsection
+      elsif name == "primary"
+        subsection + spaces + %(url: <%= ENV["DATABASE_URL"] %>\n)
+      else
+        subsection + spaces + %(url: <%= URI.parse(ENV["DATABASE_URL"]).tap { |url| url.path += "_#{name}" } if ENV["DATABASE_URL"] %>\n)
+      end
+    end
+
+    yaml.sub(section, replacement)
+  end
 end
diff --git a/lib/generators/templates/database.yml.erb b/lib/generators/templates/database.yml.erb
new file mode 100644
index 0000000..dc5c170
--- /dev/null
+++ b/lib/generators/templates/database.yml.erb
@@ -0,0 +1 @@
+<%= fix_database_config %>
\ No newline at end of file
diff --git a/test/base.rb b/test/base.rb
index c23a11b..ef7718c 100644
--- a/test/base.rb
+++ b/test/base.rb
@@ -110,6 +110,16 @@ def check_entrypoint
     assert_equal expected, results
   end
 
+  def check_database_config
+    results = IO.read("config/database.yml")
+
+    IO.write("#{@results}/database.yml", results) if @capture
+
+    expected = IO.read("#{@results}/database.yml")
+
+    assert_equal expected, results
+  end
+
   def teardown
     return if ENV["TEST_KEEP"]
     Dir.chdir ".."
diff --git a/test/results/postgresql/Dockerfile b/test/results/postgresql/Dockerfile
index ad69854..9427aa0 100644
--- a/test/results/postgresql/Dockerfile
+++ b/test/results/postgresql/Dockerfile
@@ -65,5 +65,5 @@ USER rails:rails
 ENTRYPOINT ["/rails/bin/docker-entrypoint"]
 
 # Start the server by default, this can be overwritten at runtime
-EXPOSE 3000
-CMD ["./bin/rails", "server"]
+EXPOSE 80
+CMD ["bundle", "exec", "thrust", "./bin/rails", "server"]
diff --git a/test/results/postgresql/database.yml b/test/results/postgresql/database.yml
new file mode 100644
index 0000000..40d1fcd
--- /dev/null
+++ b/test/results/postgresql/database.yml
@@ -0,0 +1,102 @@
+# PostgreSQL. Versions 9.3 and up are supported.
+#
+# Install the pg driver:
+#   gem install pg
+# On macOS with Homebrew:
+#   gem install pg -- --with-pg-config=/usr/local/bin/pg_config
+# On Windows:
+#   gem install pg
+#       Choose the win32 build.
+#       Install PostgreSQL and put its /bin directory on your path.
+#
+# Configure Using Gemfile
+# gem "pg"
+#
+default: &default
+  adapter: postgresql
+  encoding: unicode
+  # For details on connection pooling, see Rails configuration guide
+  # https://guides.rubyonrails.org/configuring.html#database-pooling
+  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+
+
+development:
+  <<: *default
+  database: test_postgresql_development
+
+  # The specified database role being used to connect to PostgreSQL.
+  # To create additional roles in PostgreSQL see `$ createuser --help`.
+  # When left blank, PostgreSQL will use the default role. This is
+  # the same name as the operating system user running Rails.
+  #username: test_postgresql
+
+  # The password associated with the PostgreSQL role (username).
+  #password:
+
+  # Connect on a TCP socket. Omitted by default since the client uses a
+  # domain socket that doesn't need configuration. Windows does not have
+  # domain sockets, so uncomment these lines.
+  #host: localhost
+
+  # The TCP port the server listens on. Defaults to 5432.
+  # If your server runs on a different port number, change accordingly.
+  #port: 5432
+
+  # Schema search path. The server defaults to $user,public
+  #schema_search_path: myapp,sharedapp,public
+
+  # Minimum log levels, in increasing order:
+  #   debug5, debug4, debug3, debug2, debug1,
+  #   log, notice, warning, error, fatal, and panic
+  # Defaults to warning.
+  #min_messages: notice
+
+# Warning: The database defined as "test" will be erased and
+# re-generated from your development database when you run "rake".
+# Do not set this db to the same as development or production.
+test:
+  <<: *default
+  database: test_postgresql_test
+
+# As with config/credentials.yml, you never want to store sensitive information,
+# like your database password, in your source code. If your source code is
+# ever seen by anyone, they now have access to your database.
+#
+# Instead, provide the password or a full connection URL as an environment
+# variable when you boot the app. For example:
+#
+#   DATABASE_URL="postgres://myuser:mypass@localhost/somedatabase"
+#
+# If the connection URL is provided in the special DATABASE_URL environment
+# variable, Rails will automatically merge its configuration values on top of
+# the values provided in this file. Alternatively, you can specify a connection
+# URL environment variable explicitly:
+#
+#   production:
+#     url: <%= ENV["MY_APP_DATABASE_URL"] %>
+#
+# Read https://guides.rubyonrails.org/configuring.html#configuring-a-database
+# for a full overview on how database connection configuration can be specified.
+#
+production:
+  primary: &primary_production
+    <<: *default
+    database: test_postgresql_production
+    username: test_postgresql
+    password: <%= ENV["TEST_POSTGRESQL_DATABASE_PASSWORD"] %>
+    url: <%= ENV["DATABASE_URL"] %>
+  cache:
+    <<: *primary_production
+    database: test_postgresql_production_cache
+    migrations_paths: db/cache_migrate
+    url: <%= URI.parse(ENV["DATABASE_URL"]).tap { |url| url.path += "_cache" } if ENV["DATABASE_URL"] %>
+  queue:
+    <<: *primary_production
+    database: test_postgresql_production_queue
+    migrations_paths: db/queue_migrate
+    url: <%= URI.parse(ENV["DATABASE_URL"]).tap { |url| url.path += "_queue" } if ENV["DATABASE_URL"] %>
+  cable:
+    <<: *primary_production
+    database: test_postgresql_production_cable
+    migrations_paths: db/cable_migrate
+    url: <%= URI.parse(ENV["DATABASE_URL"]).tap { |url| url.path += "_cable" } if ENV["DATABASE_URL"] %>
diff --git a/test/test_postgres.rb b/test/test_postgres.rb
index c19ecf6..944530c 100644
--- a/test/test_postgres.rb
+++ b/test/test_postgres.rb
@@ -3,11 +3,12 @@
 require_relative "base"
 
 class TestPostgresql < TestBase
-  @rails_options = "--database=postgresql"
+  @rails_options = "--database=postgresql --main"
   @generate_options = "--compose"
 
   def test_postgresql
     check_dockerfile
     check_compose
+    check_database_config
   end
 end