PHPLIB-445: Leave key as-is if ChangeStream::next() fails to extract resume token

Author: jmikola

src/ChangeStream.php

@@ -104,11 +104,11 @@ public function next()
         try {
             $this->csIt->next();
             if ($this->valid()) {
+                $this->resumeToken = $this->extractResumeToken($this->csIt->current());
                 if ($this->hasAdvanced) {
                     $this->key++;
                 }
                 $this->hasAdvanced = true;
-                $this->resumeToken = $this->extractResumeToken($this->csIt->current());
             }
             /* If the cursorId is 0, the server has invalidated the cursor so we
              * will never perform another getMore. This means that we cannot

tests/Operation/WatchFunctionalTest.php

@@ -642,7 +642,7 @@ public function testNextAdvancesKey()
         $this->assertSame(1, $changeStream->key());
     }
 
-    public function testResumeTokenNotFoundAdvancesKey()
+    public function testResumeTokenNotFoundDoesNotAdvanceKey()
     {
         if (version_compare($this->getServerVersion(), '4.1.8', '>=')) {
             $this->markTestSkipped('Server rejects change streams that modify resume token (SERVER-37786)');
@@ -653,8 +653,6 @@ public function testResumeTokenNotFoundAdvancesKey()
         $operation = new Watch($this->manager, $this->getDatabaseName(), $this->getCollectionName(), $pipeline, $this->defaultOptions);
         $changeStream = $operation->execute($this->getPrimaryServer());
 
-        /* Note: we intentionally do not start iteration with rewind() to ensure
-         * that we test extraction functionality within next(). */
         $this->insertDocument(['x' => 1]);
         $this->insertDocument(['x' => 2]);
         $this->insertDocument(['x' => 3]);
@@ -671,14 +669,14 @@ public function testResumeTokenNotFoundAdvancesKey()
             $this->fail('ResumeTokenException was not thrown');
         } catch (ResumeTokenException $e) {}
 
-        $this->assertSame(1, $changeStream->key());
+        $this->assertSame(0, $changeStream->key());
 
         try {
             $changeStream->next();
             $this->fail('ResumeTokenException was not thrown');
         } catch (ResumeTokenException $e) {}
 
-        $this->assertSame(2, $changeStream->key());
+        $this->assertSame(0, $changeStream->key());
     }
 
     public function testSessionPersistsAfterResume()