Merge pull request #11014 from senny/10936_inspect_does_not_crash_without_connection

`inspect` for AR model classes does not initiate a new connection.

activerecord/CHANGELOG.md

+*   `inspect` on Active Record model classes does not initiate a
+    new connection. This means that calling `inspect`, when the
+    database is missing, will no longer raise an exception.
+    Fixes #10936.
+
+    Example:
+
+        Author.inspect # => "Author(no database connection)"
+
+    *Yves Senn*
+
 *   Handle single quotes in PostgreSQL default column values.
     Fixes #10881.
 

activerecord/lib/active_record/core.rb

@@ -123,6 +123,8 @@ def inspect
           super
         elsif abstract_class?
           "#{super}(abstract)"
+        elsif !connected?
+          "#{super}(no database connection)"
         elsif table_exists?
           attr_list = columns.map { |c| "#{c.name}: #{c.type}" } * ', '
           "#{super}(#{attr_list})"

activerecord/test/cases/invalid_connection_test.rb

+require "cases/helper"
+require "models/bird"
+
+class TestAdapterWithInvalidConnection < ActiveRecord::TestCase
+  self.use_transactional_fixtures = false
+
+  def setup
+    @spec = ActiveRecord::Base.connection_config
+    non_existing_spec = {adapter: @spec[:adapter], database: "i_do_not_exist"}
+    ActiveRecord::Base.establish_connection(non_existing_spec)
+  end
+
+  def teardown
+    ActiveRecord::Base.establish_connection(@spec)
+  end
+
+  test "inspect on Model class does not raise" do
+    assert_equal "Bird(no database connection)", Bird.inspect
+  end
+end