Deprecate check_pending! in favor of check_all_pending!

`check_pending!` takes a connection that defaults to `Base.connection`
(or migration_connection but right now that's always Base.connection).
This means that we aren't able to loop through all the configs for an
environment because this is a public API that accepts a single
connection. To fix this I've deprecated `check_pending!` in favor of
`check_all_pending!` which will loop through the configs and check for
pending migrations on all the connections.

Example results:

```
Migrations are pending. To resolve this issue, run:

        bin/rails db:migrate

You have 3 pending migrations:

db/migrate/20221213152217_create_posts.rb
db/migrate/20230503150812_add_active_column_to_posts.rb
db/secondary_migrate/20230503173111_create_dogs.rb
```

Before this change, only migrations in `db/migrate` or
`db/secondary_migrate` would be output by `ActiveRecord::Migration.check_pending!`.
I chose not to accept a connection or db_config argument for this new
method because it's not super useful. It's more useful to know all
pending migrations. If it becomes problematic, we can reimplement the
connection option on this method (or reintroduce `check_pending!`.

Author: eileencodes

activerecord/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Deprecate `check_pending!` in favor of `check_pending_migrations!`.
+
+    `check_pending!` will only check for pending migrations on the current database connection or the one passed in. This has been deprecated in favor of `check_pending_migrations!` which will find all pending migrations for the database configurations in a given environment.
+
+    *Eileen M. Uchitelle*
+
 *   Make `increment_counter`/`decrement_counter` accept an amount argument
 
     ```ruby

activerecord/lib/active_record/migration.rb

@@ -643,8 +643,38 @@ def nearest_delegate # :nodoc:
       end
 
       # Raises <tt>ActiveRecord::PendingMigrationError</tt> error if any migrations are pending.
+      #
+      # This is deprecated in favor of +check_pending_migrations!+
       def check_pending!(connection = ActiveRecord::Tasks::DatabaseTasks.migration_connection)
-        raise ActiveRecord::PendingMigrationError if connection.migration_context.needs_migration?
+        ActiveRecord.deprecator.warn(<<-MSG.squish)
+          The `check_pending!` method is deprecated in favor of `check_pending_migrations!`. The
+          new implementation will loop through all available database configurations and find
+          pending migrations. The prior implementation did not permit this.
+        MSG
+
+        pending_migrations = connection.migration_context.open.pending_migrations
+
+        if pending_migrations.any?
+          raise ActiveRecord::PendingMigrationError.new(pending_migrations: pending_migrations)
+        end
+      end
+
+      # Raises <tt>ActiveRecord::PendingMigrationError</tt> error if any migrations are pending
+      # for all database configurations in an environment.
+      def check_all_pending!
+        pending_migrations = []
+
+        ActiveRecord::Tasks::DatabaseTasks.with_temporary_connection_for_each(env: env) do |connection|
+          if pending = connection.migration_context.open.pending_migrations
+            pending_migrations << pending
+          end
+        end
+
+        migrations = pending_migrations.flatten
+
+        if migrations.any?
+          raise ActiveRecord::PendingMigrationError.new(pending_migrations: migrations)
+        end
       end
 
       def load_schema_if_pending!

activerecord/test/cases/migration/pending_migrations_test.rb

@@ -44,6 +44,11 @@ def test_errors_if_pending
           assert_pending_migrations("01_create_foo.rb")
         end
 
+        def test_errors_if_pending_with_deprecated_method
+          create_migration "01", "create_foo"
+          assert_deprecated_check_pending("01_create_foo.rb")
+        end
+
         def test_checks_if_supported
           run_migrations
           assert_no_pending_migrations
@@ -87,10 +92,29 @@ def test_with_stdlib_logger
         end
 
         private
+          def assert_deprecated_check_pending(*expected_migrations)
+            2.times do
+              assert_raises ActiveRecord::PendingMigrationError do
+                assert_deprecated(ActiveRecord.deprecator) do
+                  ActiveRecord::Migration.check_pending!
+                end
+              end
+
+              error = assert_raises ActiveRecord::PendingMigrationError do
+                CheckPending.new(proc { flunk }).call({})
+              end
+
+              assert_includes error.message, "Migrations are pending."
+              expected_migrations.each do |migration|
+                assert_includes error.message, migration
+              end
+            end
+          end
+
           def assert_pending_migrations(*expected_migrations)
             2.times do
               assert_raises ActiveRecord::PendingMigrationError do
-                ActiveRecord::Migration.check_pending!
+                ActiveRecord::Migration.check_all_pending!
               end
 
               error = assert_raises ActiveRecord::PendingMigrationError do
@@ -110,7 +134,7 @@ def assert_no_pending_migrations
 
             2.times do
               assert_nothing_raised do
-                ActiveRecord::Migration.check_pending!
+                ActiveRecord::Migration.check_all_pending!
               end
 
               app.expect :call, nil, [{}]