fix(config): Throw PreconditionException always when it didn't matchbackport/47933/stable30

Previously even when the precondition did not match, the call "passed"
when the after value was the expected one. This however can lead to
race conditions, duplicate code excutions and other things.

Signed-off-by: Joas Schilling <coding@schilljs.com>

2 files changed, 39 insertions, 3 deletions

diff --git a/lib/private/AllConfig.php b/lib/private/AllConfig.php
index 58eee772fbf..d48de298fad 100644
--- a/lib/private/AllConfig.php
+++ b/lib/private/AllConfig.php
@@ -242,10 +242,10 @@ class AllConfig implements IConfig {
 		$prevValue = $this->getUserValue($userId, $appName, $key, null);
 
 		if ($prevValue !== null) {
-			if ($prevValue === (string)$value) {
-				return;
-			} elseif ($preCondition !== null && $prevValue !== (string)$preCondition) {
+			if ($preCondition !== null && $prevValue !== (string)$preCondition) {
 				throw new PreConditionNotMetException();
+			} elseif ($prevValue === (string)$value) {
+				return;
 			} else {
 				$qb = $this->connection->getQueryBuilder();
 				$qb->update('preferences')
diff --git a/tests/lib/AllConfigTest.php b/tests/lib/AllConfigTest.php
index c703c47c94e..48df3416df1 100644
--- a/tests/lib/AllConfigTest.php
+++ b/tests/lib/AllConfigTest.php
@@ -182,6 +182,42 @@ class AllConfigTest extends \Test\TestCase {
 		$config->deleteUserValue('userPreCond1', 'appPreCond', 'keyPreCond');
 	}
 
+	public function testSetUserValueWithPreConditionFailureWhenResultStillMatches(): void {
+		$this->expectException(\OCP\PreConditionNotMetException::class);
+
+		$config = $this->getConfig();
+
+		$selectAllSQL = 'SELECT `userid`, `appid`, `configkey`, `configvalue` FROM `*PREFIX*preferences` WHERE `userid` = ?';
+
+		$config->setUserValue('userPreCond1', 'appPreCond', 'keyPreCond', 'valuePreCond');
+
+		$result = $this->connection->executeQuery($selectAllSQL, ['userPreCond1'])->fetchAll();
+
+		$this->assertCount(1, $result);
+		$this->assertEquals([
+			'userid' => 'userPreCond1',
+			'appid' => 'appPreCond',
+			'configkey' => 'keyPreCond',
+			'configvalue' => 'valuePreCond'
+		], $result[0]);
+
+		// test if the method throws with invalid precondition when the value is the same
+		$config->setUserValue('userPreCond1', 'appPreCond', 'keyPreCond', 'valuePreCond', 'valuePreCond3');
+
+		$result = $this->connection->executeQuery($selectAllSQL, ['userPreCond1'])->fetchAll();
+
+		$this->assertCount(1, $result);
+		$this->assertEquals([
+			'userid' => 'userPreCond1',
+			'appid' => 'appPreCond',
+			'configkey' => 'keyPreCond',
+			'configvalue' => 'valuePreCond'
+		], $result[0]);
+
+		// cleanup
+		$config->deleteUserValue('userPreCond1', 'appPreCond', 'keyPreCond');
+	}
+
 	public function testSetUserValueUnchanged() {
 		// TODO - FIXME until the dependency injection is handled properly (in AllConfig)
 		$this->markTestSkipped('Skipped because this is just testable if database connection can be injected');