diff --git a/src/Symfony/Component/EventDispatcher/Tests/Debug/TraceableEventDispatcherTest.php b/src/Symfony/Component/EventDispatcher/Tests/Debug/TraceableEventDispatcherTest.php
index b2437dc1fc..4462519196 100644
--- a/src/Symfony/Component/EventDispatcher/Tests/Debug/TraceableEventDispatcherTest.php
+++ b/src/Symfony/Component/EventDispatcher/Tests/Debug/TraceableEventDispatcherTest.php
@@ -12,6 +12,7 @@
 namespace Symfony\Component\EventDispatcher\Tests\Debug;
 
 use PHPUnit\Framework\TestCase;
+use Symfony\Component\Debug\BufferingLogger;
 use Symfony\Component\EventDispatcher\Debug\TraceableEventDispatcher;
 use Symfony\Component\EventDispatcher\Event;
 use Symfony\Component\EventDispatcher\EventDispatcher;
@@ -206,41 +207,57 @@ class TraceableEventDispatcherTest extends TestCase
 
     public function testLogger()
     {
-        $logger = $this->getMockBuilder('Psr\Log\LoggerInterface')->getMock();
+        $logger = new BufferingLogger();
 
         $dispatcher = new EventDispatcher();
         $tdispatcher = new TraceableEventDispatcher($dispatcher, new Stopwatch(), $logger);
         $tdispatcher->addListener('foo', $listener1 = function () {});
         $tdispatcher->addListener('foo', $listener2 = function () {});
 
-        $logger->expects($this->exactly(2))
-            ->method('debug')
-            ->withConsecutive(
-                ['Notified event "{event}" to listener "{listener}".', ['event' => 'foo', 'listener' => 'closure']],
-                ['Notified event "{event}" to listener "{listener}".', ['event' => 'foo', 'listener' => 'closure']]
-            );
-
         $tdispatcher->dispatch(new Event(), 'foo');
+
+        $this->assertSame([
+            [
+                'debug',
+                'Notified event "{event}" to listener "{listener}".',
+                ['event' => 'foo', 'listener' => 'closure'],
+            ],
+            [
+                'debug',
+                'Notified event "{event}" to listener "{listener}".',
+                ['event' => 'foo', 'listener' => 'closure'],
+            ],
+        ], $logger->cleanLogs());
     }
 
     public function testLoggerWithStoppedEvent()
     {
-        $logger = $this->getMockBuilder('Psr\Log\LoggerInterface')->getMock();
+        $logger = new BufferingLogger();
 
         $dispatcher = new EventDispatcher();
         $tdispatcher = new TraceableEventDispatcher($dispatcher, new Stopwatch(), $logger);
         $tdispatcher->addListener('foo', $listener1 = function (Event $event) { $event->stopPropagation(); });
         $tdispatcher->addListener('foo', $listener2 = function () {});
 
-        $logger->expects($this->exactly(3))
-            ->method('debug')
-            ->withConsecutive(
-                ['Notified event "{event}" to listener "{listener}".', ['event' => 'foo', 'listener' => 'closure']],
-                ['Listener "{listener}" stopped propagation of the event "{event}".', ['event' => 'foo', 'listener' => 'closure']],
-                ['Listener "{listener}" was not called for event "{event}".', ['event' => 'foo', 'listener' => 'closure']]
-            );
-
         $tdispatcher->dispatch(new Event(), 'foo');
+
+        $this->assertSame([
+            [
+                'debug',
+                'Notified event "{event}" to listener "{listener}".',
+                ['event' => 'foo', 'listener' => 'closure'],
+            ],
+            [
+                'debug',
+                'Listener "{listener}" stopped propagation of the event "{event}".',
+                ['event' => 'foo', 'listener' => 'closure'],
+            ],
+            [
+                'debug',
+                'Listener "{listener}" was not called for event "{event}".',
+                ['event' => 'foo', 'listener' => 'closure'],
+            ],
+        ], $logger->cleanLogs());
     }
 
     public function testDispatchCallListeners()
diff --git a/src/Symfony/Component/EventDispatcher/composer.json b/src/Symfony/Component/EventDispatcher/composer.json
index 62bea6cb11..16c35a156c 100644
--- a/src/Symfony/Component/EventDispatcher/composer.json
+++ b/src/Symfony/Component/EventDispatcher/composer.json
@@ -23,6 +23,7 @@
         "symfony/dependency-injection": "^3.4|^4.0|^5.0",
         "symfony/expression-language": "^3.4|^4.0|^5.0",
         "symfony/config": "^3.4|^4.0|^5.0",
+        "symfony/debug": "~3.4|~4.4",
         "symfony/http-foundation": "^3.4|^4.0|^5.0",
         "symfony/service-contracts": "^1.1|^2",
         "symfony/stopwatch": "^3.4|^4.0|^5.0",
diff --git a/src/Symfony/Component/Yaml/Inline.php b/src/Symfony/Component/Yaml/Inline.php
index bb1e1f1590..3875144dc1 100644
--- a/src/Symfony/Component/Yaml/Inline.php
+++ b/src/Symfony/Component/Yaml/Inline.php
@@ -90,7 +90,7 @@ class Inline
             }
 
             // some comments are allowed at the end
-            if (preg_replace('/\s+#.*$/A', '', substr($value, $i))) {
+            if (preg_replace('/\s*#.*$/A', '', substr($value, $i))) {
                 throw new ParseException(sprintf('Unexpected characters near "%s".', substr($value, $i)), self::$parsedLineNumber + 1, $value, self::$parsedFilename);
             }
 
diff --git a/src/Symfony/Component/Yaml/Parser.php b/src/Symfony/Component/Yaml/Parser.php
index b5e19dd692..997de27965 100644
--- a/src/Symfony/Component/Yaml/Parser.php
+++ b/src/Symfony/Component/Yaml/Parser.php
@@ -102,6 +102,7 @@ class Parser
             $this->refs = [];
             $this->skippedLineNumbers = [];
             $this->locallySkippedLineNumbers = [];
+            $this->totalNumberOfLines = null;
         }
 
         return $data;
diff --git a/src/Symfony/Component/Yaml/Tests/InlineTest.php b/src/Symfony/Component/Yaml/Tests/InlineTest.php
index c2f79c8530..b4143b9c17 100644
--- a/src/Symfony/Component/Yaml/Tests/InlineTest.php
+++ b/src/Symfony/Component/Yaml/Tests/InlineTest.php
@@ -799,6 +799,16 @@ class InlineTest extends TestCase
         self::assertSame('-0123456789', Inline::parse('-0123456789'));
     }
 
+    public function testParseCommentNotPrefixedBySpaces()
+    {
+        self::assertSame('foo', Inline::parse('"foo"#comment'));
+    }
+
+    public function testParseUnquotedStringContainingHashTagNotPrefixedBySpace()
+    {
+        self::assertSame('foo#nocomment', Inline::parse('foo#nocomment'));
+    }
+
     /**
      * @dataProvider unquotedExclamationMarkThrowsProvider
      */
diff --git a/src/Symfony/Component/Yaml/Tests/ParserTest.php b/src/Symfony/Component/Yaml/Tests/ParserTest.php
index 2c19375c25..ce682228ac 100644
--- a/src/Symfony/Component/Yaml/Tests/ParserTest.php
+++ b/src/Symfony/Component/Yaml/Tests/ParserTest.php
@@ -2438,6 +2438,39 @@ YAML;
             $this->parser->parse($yaml)
         );
     }
+
+    /**
+     * This is a regression test for a bug where a YAML block with a nested multiline string using | was parsed without
+     * a trailing \n when a shorter YAML document was parsed before.
+     *
+     * When a shorter document was parsed before, the nested string did not have a \n at the end of the string, because
+     * the Parser thought it was the end of the file, even though it is not.
+     */
+    public function testParsingMultipleDocuments()
+    {
+        $shortDocument = 'foo: bar';
+        $longDocument = <<<YAML
+a:
+    b: |
+        row
+        row2
+c: d
+YAML;
+
+        $expected = ['a' => ['b' => "row\nrow2\n"], 'c' => 'd'];
+
+        // The parser was not used before, so there is a new line after row2
+        $this->assertSame($expected, $this->parser->parse($longDocument));
+
+        $parser = new Parser();
+        // The first parsing set and fixed the totalNumberOfLines in the Parser before, so parsing the short document here
+        // to reproduce the issue. If the issue would not have been fixed, the next assertion will fail
+        $parser->parse($shortDocument);
+
+        // After the total number of lines has been rset the result will be the same as if a new parser was used
+        // (before, there was no \n after row2)
+        $this->assertSame($expected, $parser->parse($longDocument));
+    }
 }
 
 class B