diff --git a/src/Symfony/Component/Yaml/Dumper.php b/src/Symfony/Component/Yaml/Dumper.php
index 52db38c3b032b..67102ed62c03b 100644
--- a/src/Symfony/Component/Yaml/Dumper.php
+++ b/src/Symfony/Component/Yaml/Dumper.php
@@ -29,6 +29,13 @@ class Dumper
      */
     protected $indentation;
 
+    /**
+     * String of spaces with length equal to $this->indentation.
+     *
+     * @var string
+     */
+    private $indentStr;
+
     public function __construct(int $indentation = 4)
     {
         if ($indentation < 1) {
@@ -36,6 +43,7 @@ public function __construct(int $indentation = 4)
         }
 
         $this->indentation = $indentation;
+        $this->indentStr = str_repeat(' ', $indentation);
     }
 
     /**
@@ -50,93 +58,106 @@ public function __construct(int $indentation = 4)
      */
     public function dump($input, int $inline = 0, int $indent = 0, int $flags = 0): string
     {
-        $output = '';
         $prefix = $indent ? str_repeat(' ', $indent) : '';
-        $dumpObjectAsInlineMap = true;
 
-        if (Yaml::DUMP_OBJECT_AS_MAP & $flags && ($input instanceof \ArrayObject || $input instanceof \stdClass)) {
-            $dumpObjectAsInlineMap = empty((array) $input);
+        $tag = null;
+        if ($input instanceof TaggedValue) {
+            $tag = $input->getTag();
+            $input = $input->getValue();
+            if ($input instanceof TaggedValue) {
+                throw new \InvalidArgumentException('Nested tags are not supported.');
+            }
         }
 
-        if ($inline <= 0 || (!\is_array($input) && !$input instanceof TaggedValue && $dumpObjectAsInlineMap) || empty($input)) {
-            $output .= $prefix.Inline::dump($input, $flags);
-        } else {
-            $dumpAsMap = Inline::isHash($input);
-
-            foreach ($input as $key => $value) {
-                if ('' !== $output && "\n" !== $output[-1]) {
-                    $output .= "\n";
-                }
-
-                if (Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK & $flags && \is_string($value) && false !== strpos($value, "\n") && false === strpos($value, "\r")) {
-                    // If the first line starts with a space character, the spec requires a blockIndicationIndicator
-                    // http://www.yaml.org/spec/1.2/spec.html#id2793979
-                    $blockIndentationIndicator = (' ' === substr($value, 0, 1)) ? (string) $this->indentation : '';
-
-                    if (isset($value[-2]) && "\n" === $value[-2] && "\n" === $value[-1]) {
-                        $blockChompingIndicator = '+';
-                    } elseif ("\n" === $value[-1]) {
-                        $blockChompingIndicator = '';
-                    } else {
-                        $blockChompingIndicator = '-';
-                    }
+        if ($this->shouldDumpAsInline($inline, $input, $flags)) {
+            return $prefix
+                .(null !== $tag ? '!'.$tag.' ' : '')
+                .Inline::dump($input, $flags)
+            ;
+        }
 
-                    $output .= sprintf('%s%s%s |%s%s', $prefix, $dumpAsMap ? Inline::dump($key, $flags).':' : '-', '', $blockIndentationIndicator, $blockChompingIndicator);
+        $dumpAsMap = Inline::isHash($input);
 
-                    foreach (explode("\n", $value) as $row) {
-                        if ('' === $row) {
-                            $output .= "\n";
-                        } else {
-                            $output .= sprintf("\n%s%s%s", $prefix, str_repeat(' ', $this->indentation), $row);
-                        }
-                    }
-
-                    continue;
-                }
+        $output = '';
+        foreach ($input as $key => $value) {
+            if ('' !== $output && "\n" !== $output[-1]) {
+                $output .= "\n";
+            }
+            $output .= $prefix;
+            $output .= $dumpAsMap ? Inline::dump($key, $flags).':' : '-';
 
+            $tagged = false;
+            if ($value instanceof TaggedValue) {
+                $output .= ' !'.$value->getTag();
+                $value = $value->getValue();
                 if ($value instanceof TaggedValue) {
-                    $output .= sprintf('%s%s !%s', $prefix, $dumpAsMap ? Inline::dump($key, $flags).':' : '-', $value->getTag());
+                    throw new \InvalidArgumentException('Nested tags are not supported.');
+                }
+                $tagged = true;
+            }
 
-                    if (Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK & $flags && \is_string($value->getValue()) && false !== strpos($value->getValue(), "\n") && false === strpos($value->getValue(), "\r\n")) {
-                        // If the first line starts with a space character, the spec requires a blockIndicationIndicator
-                        // http://www.yaml.org/spec/1.2/spec.html#id2793979
-                        $blockIndentationIndicator = (' ' === substr($value->getValue(), 0, 1)) ? (string) $this->indentation : '';
-                        $output .= sprintf(' |%s', $blockIndentationIndicator);
+            if (Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK & $flags && \is_string($value) && false !== strpos($value, "\n") && false === strpos($value, "\r")) {
+                $output .= ' |';
+                // If the first line starts with a space character, the spec requires a blockIndicationIndicator
+                // http://www.yaml.org/spec/1.2/spec.html#id2793979
+                if (' ' === substr($value, 0, 1)) {
+                    $output .= $this->indentation;
+                }
 
-                        foreach (explode("\n", $value->getValue()) as $row) {
-                            $output .= sprintf("\n%s%s%s", $prefix, str_repeat(' ', $this->indentation), $row);
-                        }
+                if (isset($value[-2]) && "\n" === $value[-2] && "\n" === $value[-1]) {
+                    $output .= '+';
+                } elseif ("\n" !== $value[-1]) {
+                    $output .= '-';
+                }
 
-                        continue;
+                foreach (explode("\n", $value) as $row) {
+                    $output .= "\n";
+                    if ('' !== $row) {
+                        $output .= $prefix.$this->indentStr.$row;
                     }
+                }
 
-                    if ($inline - 1 <= 0 || null === $value->getValue() || \is_scalar($value->getValue())) {
-                        $output .= ' '.$this->dump($value->getValue(), $inline - 1, 0, $flags)."\n";
-                    } else {
-                        $output .= "\n";
-                        $output .= $this->dump($value->getValue(), $inline - 1, $dumpAsMap ? $indent + $this->indentation : $indent + 2, $flags);
-                    }
+                continue;
+            }
 
-                    continue;
-                }
+            $willBeInlined = $this->shouldDumpAsInline($inline - 1, $value, $flags);
+
+            $output .= ($willBeInlined ? ' ' : "\n")
+                .$this->dump(
+                    $value,
+                    $inline - 1,
+                    $willBeInlined
+                        ? 0
+                        : $indent + ($tagged && !$dumpAsMap ? 2 : $this->indentation),
+                    $flags)
+                .($willBeInlined ? "\n" : '')
+            ;
+        }
+
+        if (null !== $tag) {
+            $output = '!'.$tag."\n".$output;
+        }
 
-                $dumpObjectAsInlineMap = true;
+        return $output;
+    }
 
-                if (Yaml::DUMP_OBJECT_AS_MAP & $flags && ($value instanceof \ArrayObject || $value instanceof \stdClass)) {
-                    $dumpObjectAsInlineMap = empty((array) $value);
-                }
+    private function shouldDumpAsInline(int $inline, $value, int $flags): bool
+    {
+        if ($inline <= 0 || empty($value)) {
+            return true;
+        }
 
-                $willBeInlined = $inline - 1 <= 0 || !\is_array($value) && $dumpObjectAsInlineMap || empty($value);
+        if (\is_array($value)) {
+            return false;
+        }
 
-                $output .= sprintf('%s%s%s%s',
-                    $prefix,
-                    $dumpAsMap ? Inline::dump($key, $flags).':' : '-',
-                    $willBeInlined ? ' ' : "\n",
-                    $this->dump($value, $inline - 1, $willBeInlined ? 0 : $indent + $this->indentation, $flags)
-                ).($willBeInlined ? "\n" : '');
-            }
+        if (Yaml::DUMP_OBJECT_AS_MAP & $flags
+            && ($value instanceof \ArrayObject || $value instanceof \stdClass)
+            && !empty((array) $value)
+        ) {
+            return false;
         }
 
-        return $output;
+        return true;
     }
 }
diff --git a/src/Symfony/Component/Yaml/Tests/DumperTest.php b/src/Symfony/Component/Yaml/Tests/DumperTest.php
index 59a47a8130f31..164b01c7e74b9 100644
--- a/src/Symfony/Component/Yaml/Tests/DumperTest.php
+++ b/src/Symfony/Component/Yaml/Tests/DumperTest.php
@@ -443,20 +443,20 @@ public function testDumpingTaggedValueTopLevelAssocInline()
     public function testDumpingTaggedValueTopLevelAssoc()
     {
         $data = new TaggedValue('user', ['name' => 'jane']);
+        $expected = <<<'YAML'
+!user
+name: jane
 
-        // @todo Fix the dumper, the output should not be ''.
-        $expected = '';
-        $yaml = $this->dumper->dump($data, 2);
-        $this->assertSame($expected, $yaml);
+YAML;
+        $this->assertSame($expected, $this->dumper->dump($data, 2));
     }
 
     public function testDumpingTaggedValueTopLevelMultiLine()
     {
         $data = new TaggedValue('text', "a\nb\n");
-
-        // @todo Fix the dumper, the output should not be ''.
-        $expected = '';
+        $expected = '!text "a\\nb\\n"';
         $this->assertSame($expected, $this->dumper->dump($data, 2, 0, Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK));
+        $this->assertEquals($data, $this->parser->parse($expected, Yaml::PARSE_CUSTOM_TAGS));
     }
 
     public function testDumpingTaggedValueSpecialCharsInTag()
@@ -588,7 +588,7 @@ public function testDumpingMultiLineStringAsScalarBlockTaggedValue()
         $data = [
             'foo' => new TaggedValue('bar', "foo\nline with trailing spaces:\n  \nbar\ninteger like line:\n123456789\nempty line:\n\nbaz"),
         ];
-        $expected = "foo: !bar |\n".
+        $expected = "foo: !bar |-\n".
             "    foo\n".
             "    line with trailing spaces:\n".
             "      \n".
@@ -596,7 +596,7 @@ public function testDumpingMultiLineStringAsScalarBlockTaggedValue()
             "    integer like line:\n".
             "    123456789\n".
             "    empty line:\n".
-            "    \n".
+            "\n".
             '    baz';
 
         $this->assertSame($expected, $this->dumper->dump($data, 2, 0, Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK));
@@ -608,12 +608,12 @@ public function testDumpingTaggedMultiLineInList()
         $data = [
             new TaggedValue('bar', "a\nb"),
         ];
-        $expected = "- !bar |\n    a\n    b";
+        $expected = "- !bar |-\n    a\n    b";
         $this->assertSame($expected, $this->dumper->dump($data, 2, 0, Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK));
 
         // @todo Fix the parser, eliminate these exceptions.
         $this->expectException(ParseException::class);
-        $this->expectExceptionMessage('Unable to parse at line 3 (near "!bar |").');
+        $this->expectExceptionMessage('Unable to parse at line 3 (near "!bar |-").');
 
         $this->parser->parse($expected, Yaml::PARSE_CUSTOM_TAGS);
     }
@@ -623,14 +623,11 @@ public function testDumpingTaggedMultiLineTrailingNewlinesInMap()
         $data = [
             'foo' => new TaggedValue('bar', "a\nb\n\n\n"),
         ];
-        $expected = "foo: !bar |\n    a\n    b\n    \n    \n    ";
+        $expected = "foo: !bar |+\n    a\n    b\n\n\n";
         $this->assertSame($expected, $this->dumper->dump($data, 2, 0, Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK));
 
-        // @todo Fix the parser, the result should be identical to $data.
         $this->assertSameData(
-            [
-                'foo' => new TaggedValue('bar', "a\nb\n"),
-            ],
+            $data,
             $this->parser->parse($expected, Yaml::PARSE_CUSTOM_TAGS));
     }
 
@@ -639,12 +636,12 @@ public function testDumpingTaggedMultiLineTrailingNewlinesInList()
         $data = [
             new TaggedValue('bar', "a\nb\n\n\n"),
         ];
-        $expected = "- !bar |\n    a\n    b\n    \n    \n    ";
+        $expected = "- !bar |+\n    a\n    b\n\n\n";
         $this->assertSame($expected, $this->dumper->dump($data, 2, 0, Yaml::DUMP_MULTI_LINE_LITERAL_BLOCK));
 
         // @todo Fix the parser, eliminate these exceptions.
         $this->expectException(ParseException::class);
-        $this->expectExceptionMessage('Unable to parse at line 6 (near "!bar |").');
+        $this->expectExceptionMessage('Unable to parse at line 6 (near "!bar |+").');
 
         $this->parser->parse($expected, Yaml::PARSE_CUSTOM_TAGS);
     }
@@ -696,7 +693,7 @@ public function testDumpMultiLineStringAsScalarBlock()
     nested_inlined_multi_line_string: { inlined_multi_line: "foo\nbar\r\nempty line:\n\nbaz" }
 
 YAML
-);
+        );
         $this->assertSame($expected, $yml);
         $this->assertSame($data, $this->parser->parse($yml));
     }