`dump_schema_after_migration` applies migration tasks other than db:migrate

Closes #20743.

The task `db:_dump` now only dumps the schema if
`ActiveRecord::Base.dump_schema_after_migration` is true. This has
effects:

- `db:migrate:up`
- `db:migrate:down`
- `db:forward`
- `db:rollback`

3 files changed, 27 insertions, 15 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 794bb779fa..109f6f3cd4 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   `ActiveRecord::Base.dump_schema_after_migration` applies migration tasks
+    other than `db:migrate`. (eg. `db:rollback`, `db:migrate:dup`, ...)
+
+    Fixes #20743.
+
+    *Yves Senn*
+
 *   Add alternate syntax to make `change_column_default` reversible.
 
     User can pass in `:from` and `:to` to make `change_column_default` command
diff --git a/activerecord/lib/active_record/railties/databases.rake b/activerecord/lib/active_record/railties/databases.rake
index 66fb3ae44b..85734aea90 100644
--- a/activerecord/lib/active_record/railties/databases.rake
+++ b/activerecord/lib/active_record/railties/databases.rake
@@ -42,19 +42,22 @@ db_namespace = namespace :db do
   desc "Migrate the database (options: VERSION=x, VERBOSE=false, SCOPE=blog)."
   task :migrate => [:environment, :load_config] do
     ActiveRecord::Tasks::DatabaseTasks.migrate
-    db_namespace['_dump'].invoke if ActiveRecord::Base.dump_schema_after_migration
+    db_namespace['_dump'].invoke
   end
 
+  # IMPORTANT: This task won't dump the schema if ActiveRecord::Base.dump_schema_after_migration is set to false
   task :_dump do
-    case ActiveRecord::Base.schema_format
-    when :ruby then db_namespace["schema:dump"].invoke
-    when :sql  then db_namespace["structure:dump"].invoke
-    else
-      raise "unknown schema format #{ActiveRecord::Base.schema_format}"
+    if ActiveRecord::Base.dump_schema_after_migration
+      case ActiveRecord::Base.schema_format
+      when :ruby then db_namespace["schema:dump"].invoke
+      when :sql  then db_namespace["structure:dump"].invoke
+      else
+        raise "unknown schema format #{ActiveRecord::Base.schema_format}"
+      end
+      # Allow this task to be called as many times as required. An example is the
+      # migrate:redo task, which calls other two internally that depend on this one.
+      db_namespace['_dump'].reenable
     end
-    # Allow this task to be called as many times as required. An example is the
-    # migrate:redo task, which calls other two internally that depend on this one.
-    db_namespace['_dump'].reenable
   end
 
   namespace :migrate do
diff --git a/railties/test/application/rake/migrations_test.rb b/railties/test/application/rake/migrations_test.rb
index 70e8908a46..2d8bd7c571 100644
--- a/railties/test/application/rake/migrations_test.rb
+++ b/railties/test/application/rake/migrations_test.rb
@@ -158,20 +158,22 @@ module ApplicationTests
         add_to_config('config.active_record.dump_schema_after_migration = false')
 
         Dir.chdir(app_path) do
-          `bin/rails generate model book title:string;
-           bin/rake db:migrate`
+          `bin/rails generate model book title:string`
+          output = `bin/rails generate model author name:string`
+          version = output =~ %r{[^/]+db/migrate/(\d+)_create_authors\.rb} && $1
 
-          assert !File.exist?("db/schema.rb")
+          `bin/rake db:migrate db:rollback db:forward db:migrate:up db:migrate:down VERSION=#{version}`
+          assert !File.exist?("db/schema.rb"), "should not dump schema when configured not to"
         end
 
         add_to_config('config.active_record.dump_schema_after_migration = true')
 
         Dir.chdir(app_path) do
-          `bin/rails generate model author name:string;
-           bin/rake db:migrate`
+          `bin/rails generate model reviews book_id:integer`
+          `bin/rake db:migrate`
 
           structure_dump = File.read("db/schema.rb")
-          assert_match(/create_table "authors"/, structure_dump)
+          assert_match(/create_table "reviews"/, structure_dump)
         end
       end