Fix local migration run without old private key

It was possible to run migration locally without providing old private
key. This way migration was performed but not dispatched, which obviously
leads to desynchronization of the federation state so let's validate sender
before performing any actual actions.

closes #7558

Changelog.md

@@ -21,6 +21,7 @@
 * Fix recipient prefill on contacts and profile page [#7599](https://github.com/diaspora/diaspora/pull/7599)
 * Display likes and reshares without login [#7583](https://github.com/diaspora/diaspora/pull/7583)
 * Fix invalid data in the database for user data export [#7614](https://github.com/diaspora/diaspora/pull/7614)
+* Fix local migration run without old private key [#7558](https://github.com/diaspora/diaspora/pull/7558)
 
 ## Features
 * Ask for confirmation when leaving a submittable comment field [#7530](https://github.com/diaspora/diaspora/pull/7530)

app/models/account_migration.rb

@@ -28,6 +28,7 @@ class AccountMigration < ApplicationRecord
   # executes a migration plan according to this AccountMigration object
   def perform!
     raise "already performed" if performed?
+    validate_sender if locally_initiated?
 
     ActiveRecord::Base.transaction do
       account_deleter.tombstone_person_and_profile
@@ -115,6 +116,10 @@ class AccountMigration < ApplicationRecord
     EphemeralUser.new(old_person.diaspora_handle, old_private_key)
   end
 
+  def validate_sender
+    sender # sender method raises exception when sender can't be instantiated
+  end
+
   def update_all_references
     update_person_references
     update_user_references if user_changed_id_locally?

spec/models/account_migration_spec.rb

@@ -127,7 +127,7 @@ describe AccountMigration, type: :model do
       include_context "with local new user"
 
       it "dispatches account migration message" do
-        expect(account_migration).to receive(:sender).and_return(old_user)
+        expect(account_migration).to receive(:sender).twice.and_return(old_user)
         dispatcher = double
         expect(dispatcher).to receive(:dispatch)
         expect(Diaspora::Federation::Dispatcher).to receive(:build)
@@ -135,6 +135,14 @@ describe AccountMigration, type: :model do
           .and_return(dispatcher)
         account_migration.perform!
       end
+
+      it "doesn't run migration if old key is not provided" do
+        expect(embedded_account_deleter).not_to receive(:tombstone_person_and_profile)
+
+        expect {
+          account_migration.perform!
+        }.to raise_error "can't build sender without old private key defined"
+      end
     end
 
     context "with local old and new users" do