txn: Fire a trigger after a transaction finalization

Fire transaction trigger after a transaction finalization. This allows
to not to view the transaction dismissed changes in case of rollback.

Fixes: #4276

src/box/txn.c

@@ -427,6 +427,12 @@ txn_commit(struct txn *txn)
 		if (txn->signature < 0)
 			goto fail;
 	}
+	/*
+	 * Engine can be NULL if transaction contains IPROTO_NOP
+	 * statements only.
+	 */
+	if (txn->engine != NULL)
+		engine_commit(txn->engine, txn);
 	/*
 	 * The transaction is in the binary log. No action below
 	 * may throw. In case an error has happened, there is
@@ -438,12 +444,6 @@ txn_commit(struct txn *txn)
 		unreachable();
 		panic("commit trigger failed");
 	}
-	/*
-	 * Engine can be NULL if transaction contains IPROTO_NOP
-	 * statements only.
-	 */
-	if (txn->engine != NULL)
-		engine_commit(txn->engine, txn);
 
 	struct txn_stmt *stmt;
 	stailq_foreach_entry(stmt, &txn->stmts, next)
@@ -475,6 +475,8 @@ txn_rollback()
 	struct txn *txn = in_txn();
 	if (txn == NULL)
 		return;
+	if (txn->engine)
+		engine_rollback(txn->engine, txn);
 	/* Rollback triggers must not throw. */
 	if (txn->has_triggers &&
 	    trigger_run(&txn->on_rollback, txn) != 0) {
@@ -482,8 +484,6 @@ txn_rollback()
 		unreachable();
 		panic("rollback trigger failed");
 	}
-	if (txn->engine)
-		engine_rollback(txn->engine, txn);
 
 	struct txn_stmt *stmt;
 	stailq_foreach_entry(stmt, &txn->stmts, next)

test/box/errinj.result

@@ -1686,3 +1686,40 @@ fio = require('fio')
 box.space.test:drop()
 ---
 ...
+-- gh-4276 - check grant privilege rollback
+_ = box.schema.user.create('testg')
+---
+...
+_ = box.schema.space.create('testg'):create_index('pk')
+---
+...
+box.error.injection.set('ERRINJ_WAL_IO', true)
+---
+- ok
+...
+-- the grant operation above fails and test hasn't any space test permissions
+box.schema.user.grant('testg', 'read,write', 'space', 'testg')
+---
+- error: Failed to write to disk
+...
+-- switch user and check they couldn't select
+box.session.su('testg')
+---
+...
+box.space.testg:select()
+---
+- error: Read access to space 'testg' is denied for user 'testg'
+...
+box.session.su('admin')
+---
+...
+box.error.injection.set('ERRINJ_WAL_IO', false)
+---
+- ok
+...
+box.schema.user.drop('testg')
+---
+...
+box.space.testg:drop()
+---
+...

test/box/errinj.test.lua

@@ -587,3 +587,18 @@ fio = require('fio')
 #fio.glob(fio.pathjoin(box.cfg.vinyl_dir, box.space.test.id, 0, '*.index.inprogress')) == 0
 
 box.space.test:drop()
+
+-- gh-4276 - check grant privilege rollback
+_ = box.schema.user.create('testg')
+_ = box.schema.space.create('testg'):create_index('pk')
+
+box.error.injection.set('ERRINJ_WAL_IO', true)
+-- the grant operation above fails and test hasn't any space test permissions
+box.schema.user.grant('testg', 'read,write', 'space', 'testg')
+-- switch user and check they couldn't select
+box.session.su('testg')
+box.space.testg:select()
+box.session.su('admin')
+box.error.injection.set('ERRINJ_WAL_IO', false)
+box.schema.user.drop('testg')
+box.space.testg:drop()