fix(migrations): don't run with foreign keys activated

This PR deactivates and reactivates the foreign_keys in the DB for the duration of all migrations.
This prevents a cascade of deletion, when table columns are changed and tables get recreated by sequelize.

Fixes #2809

Signed-off-by: Philip Molares <philip.molares@udo.edu>

lib/models/index.js

@@ -9,6 +9,7 @@ const Umzug = require('umzug')
 // core
 const config = require('../config')
 const logger = require('../logger')
+const {isSQLite} = require("../utils");
 
 const dbconfig = cloneDeep(config.db)
 dbconfig.logging = config.debug
@@ -80,14 +81,38 @@ const umzug = new Umzug({
 db.runMigrations = async function runMigrations () {
   // checks migrations and run them if they are not already applied
   // exit in case of unsuccessful migrations
-  await umzug.up().catch(error => {
+  const savepointName = 'migration';
+  try {
+    if (isSQLite(sequelize)) {
+      // Deactivate foreign_keys for sqlite, so that sequelize does not accidentally delete data when recreating tables via cascading delete.
+      // See https://github.com/hedgedoc/hedgedoc/issues/2809
+      await sequelize.query('PRAGMA foreign_keys = OFF;')
+      await this.sequelize.query(`SAVEPOINT ${savepointName};`);
+    }
+    await umzug.up()
+    if (isSQLite(sequelize)) {
+      // Run a foreign keys integrity check
+      const foreignKeyCheckResult = await sequelize.query('PRAGMA foreign_key_check;')
+      if (foreignKeyCheckResult.length > 0) {
+        throw Error(`Foreign key violations detected: ${JSON.stringify(foreignKeyCheckResult, null, 2)}`);
+      }
+      await this.sequelize.query(`RELEASE ${savepointName};`, options);
+    }
+  } catch(error) {
+    if (isSQLite(sequelize)) {
+      await this.sequelize.query(`ROLLBACK TO ${savepointName};`)
+    }
     logger.error(error)
     logger.error(`Database migration failed.
 This can be the result of upgrading from quite old versions and requires manual database intervention.
 See https://docs.hedgedoc.org/guides/migration-troubleshooting/ for help.
 Exiting…`)
     process.exit(1)
-  })
+  } finally {
+    if (isSQLite(sequelize)) {
+      await sequelize.query('PRAGMA foreign_keys = ON;')
+    }
+  }
   logger.info('All migrations performed successfully')
 }