Merge branch '3.4' into 4.3

* 3.4:
  Update GitHub PR template
  don't dump a scalar tag value on its own line

.github/PULL_REQUEST_TEMPLATE.md

@@ -3,20 +3,19 @@
 | Branch?       | 4.4 for features / 3.4 or 4.3 for bug fixes <!-- see below -->
 | Bug fix?      | yes/no
 | New feature?  | yes/no <!-- please update src/**/CHANGELOG.md files -->
-| BC breaks?    | no     <!-- see https://symfony.com/bc -->
 | Deprecations? | yes/no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
-| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
+| Tickets       | Fix #... <!-- prefix each issue number with "Fix #", if any -->
-| Fixed tickets | #...   <!-- #-prefixed issue number(s), if any -->
 | License       | MIT
 | Doc PR        | symfony/symfony-docs#... <!-- required for new features -->
-
 <!--
 Replace this notice by a short README for your feature/bugfix. This will help people
 understand your PR and can be used as a start for the documentation.
 
 Additionally (see https://symfony.com/roadmap):
+ - Always add tests and ensure they pass.
+ - Never break backward compatibility (see https://symfony.com/bc).
  - Bug fixes must be submitted against the lowest maintained branch where they apply
-   (lowest branches are regularly merged to upper ones so they get the fixes too).
+   (lowest branches are regularly merged to upper ones so they get the fixes too.)
  - Features and deprecations must be submitted against branch 4.4.
  - Legacy code removals go to the master branch.
 -->

src/Symfony/Component/Yaml/Dumper.php

@@ -80,15 +80,11 @@ class Dumper
                 if ($value instanceof TaggedValue) {
                     $output .= sprintf('%s%s !%s', $prefix, $dumpAsMap ? Inline::dump($key, $flags).':' : '-', $value->getTag());
 
-                    if ($inline - 1 <= 0) {
+                    if ($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, $flags);
-
-                        if (is_scalar($value->getValue())) {
-                            $output .= "\n";
-                        }
                     }
 
                     continue;

src/Symfony/Component/Yaml/Tests/DumperTest.php

@@ -466,10 +466,21 @@ YAML;
             'user2' => new TaggedValue('user', 'john'),
         ];
         $expected = <<<YAML
-user1: !user
+user1: !user jane
-    jane
+user2: !user john
-user2: !user
+
-    john
+YAML;
+
+        $this->assertSame($expected, $this->dumper->dump($data, 2));
+    }
+
+    public function testDumpingNotInlinedNullTaggedValue()
+    {
+        $data = [
+            'foo' => new TaggedValue('bar', null),
+        ];
+        $expected = <<<YAML
+foo: !bar null
 
 YAML;