Support readonly option in SQLite3Adapter

Readonly sqlite database files are very useful as a data format for
storing configuration/lookup data that is too complicated for YAML
files.  But since such files would typically be committed to a source
control repository, it's important to ensure that they are truly safe
from being inadvertently modified.  Unfortunately using unix permissions
isn't enough, as sqlite will "helpfully" add the write bit to a database
file whenever it's written to.

sqlite3-ruby has supported a `:readonly` option since version 1.3.2 (see
https://github.com/sparklemotion/sqlite3-ruby/commit/c20c9f5dd2990042)

This simply passes that option through to the adapter if present in the
config hash.  I think this is best considered an adapter-specific option
since no other supported database has an identical concept.

2 files changed, 36 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index 544374586c..5c9912b366 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -29,9 +29,11 @@ module ActiveRecord
         Dir.mkdir(dirname) unless File.directory?(dirname)
       end
 
+      db_opts = config.symbolize_keys.merge(results_as_hash: true)
+
       db = SQLite3::Database.new(
         config[:database].to_s,
-        results_as_hash: true
+        db_opts
       )
 
       db.busy_timeout(ConnectionAdapters::SQLite3Adapter.type_cast_config_to_integer(config[:timeout])) if config[:timeout]
diff --git a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
index ad155c7492..86cbe530a0 100644
--- a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
@@ -504,6 +504,39 @@ module ActiveRecord
         assert_deprecated { @conn.valid_alter_table_type?(:string) }
       end
 
+      def test_db_is_not_readonly_when_readonly_option_is_false
+        @conn = Base.sqlite3_connection database: ":memory:",
+                                        adapter: "sqlite3",
+                                        readonly: false
+
+        assert_not_predicate(@conn.raw_connection, :readonly?)
+      end
+
+      def test_db_is_not_readonly_when_readonly_option_is_unspecified
+        @conn = Base.sqlite3_connection database: ":memory:",
+                                        adapter: "sqlite3"
+
+        assert_not_predicate(@conn.raw_connection, :readonly?)
+      end
+
+      def test_db_is_readonly_when_readonly_option_is_true
+        @conn = Base.sqlite3_connection database: ":memory:",
+                                        adapter: "sqlite3",
+                                        readonly: true
+
+        assert_predicate(@conn.raw_connection, :readonly?)
+      end
+
+      def test_writes_are_not_permitted_to_readonly_databases
+        @conn = Base.sqlite3_connection database: ":memory:",
+                                        adapter: "sqlite3",
+                                        readonly: true
+
+        assert_raises(ActiveRecord::StatementInvalid, /SQLite3::ReadOnlyException/) do
+          @conn.execute("CREATE TABLE test(id integer)")
+        end
+      end
+
       private
 
         def assert_logged(logs)