From 1fc1379028a2fb2e6675fcfbcaa2000e3e9f414b Mon Sep 17 00:00:00 2001
From: Alexandre Daubois <alex.daubois@gmail.com>
Date: Wed, 11 Sep 2024 11:49:35 +0200
Subject: [PATCH] [Yaml] Add support for dumping `null` as an empty value by
 using the `Yaml::DUMP_NULL_AS_EMPTY` flag

---
 src/Symfony/Component/Yaml/CHANGELOG.md       |  1 +
 src/Symfony/Component/Yaml/Dumper.php         | 25 +++++---
 src/Symfony/Component/Yaml/Inline.php         | 10 +++-
 .../Component/Yaml/Tests/DumperTest.php       | 57 +++++++++++++++++++
 .../Component/Yaml/Tests/ParserTest.php       | 27 +++++++++
 src/Symfony/Component/Yaml/Yaml.php           |  1 +
 6 files changed, 110 insertions(+), 11 deletions(-)

diff --git a/src/Symfony/Component/Yaml/CHANGELOG.md b/src/Symfony/Component/Yaml/CHANGELOG.md
index 05b23cd7b06fe..284c49ed0ab62 100644
--- a/src/Symfony/Component/Yaml/CHANGELOG.md
+++ b/src/Symfony/Component/Yaml/CHANGELOG.md
@@ -5,6 +5,7 @@ CHANGELOG
 ---
 
  * Deprecate parsing duplicate mapping keys whose value is `null`
+ * Add support for dumping `null` as an empty value by using the `Yaml::DUMP_NULL_AS_EMPTY` flag
 
 7.1
 ---
diff --git a/src/Symfony/Component/Yaml/Dumper.php b/src/Symfony/Component/Yaml/Dumper.php
index f8ea205a62e03..91b2ec29d5255 100644
--- a/src/Symfony/Component/Yaml/Dumper.php
+++ b/src/Symfony/Component/Yaml/Dumper.php
@@ -41,6 +41,15 @@ public function __construct(private int $indentation = 4)
      * @param int-mask-of<Yaml::DUMP_*> $flags  A bit field of Yaml::DUMP_* constants to customize the dumped YAML string
      */
     public function dump(mixed $input, int $inline = 0, int $indent = 0, int $flags = 0): string
+    {
+        if ($flags & Yaml::DUMP_NULL_AS_EMPTY && $flags & Yaml::DUMP_NULL_AS_TILDE) {
+            throw new \InvalidArgumentException('The Yaml::DUMP_NULL_AS_EMPTY and Yaml::DUMP_NULL_AS_TILDE flags cannot be used together.');
+        }
+
+        return $this->doDump($input, $inline, $indent, $flags);
+    }
+
+    private function doDump(mixed $input, int $inline = 0, int $indent = 0, int $flags = 0, int $nestingLevel = 0): string
     {
         $output = '';
         $prefix = $indent ? str_repeat(' ', $indent) : '';
@@ -51,9 +60,9 @@ public function dump(mixed $input, int $inline = 0, int $indent = 0, int $flags
         }
 
         if ($inline <= 0 || (!\is_array($input) && !$input instanceof TaggedValue && $dumpObjectAsInlineMap) || !$input) {
-            $output .= $prefix.Inline::dump($input, $flags);
+            $output .= $prefix.Inline::dump($input, $flags, 0 === $nestingLevel);
         } elseif ($input instanceof TaggedValue) {
-            $output .= $this->dumpTaggedValue($input, $inline, $indent, $flags, $prefix);
+            $output .= $this->dumpTaggedValue($input, $inline, $indent, $flags, $prefix, $nestingLevel);
         } else {
             $dumpAsMap = Inline::isHash($input);
 
@@ -105,10 +114,10 @@ public function dump(mixed $input, int $inline = 0, int $indent = 0, int $flags
                     }
 
                     if ($inline - 1 <= 0 || null === $value->getValue() || \is_scalar($value->getValue())) {
-                        $output .= ' '.$this->dump($value->getValue(), $inline - 1, 0, $flags)."\n";
+                        $output .= ' '.$this->doDump($value->getValue(), $inline - 1, 0, $flags, $nestingLevel + 1)."\n";
                     } else {
                         $output .= "\n";
-                        $output .= $this->dump($value->getValue(), $inline - 1, $dumpAsMap ? $indent + $this->indentation : $indent + 2, $flags);
+                        $output .= $this->doDump($value->getValue(), $inline - 1, $dumpAsMap ? $indent + $this->indentation : $indent + 2, $flags, $nestingLevel + 1);
                     }
 
                     continue;
@@ -126,7 +135,7 @@ public function dump(mixed $input, int $inline = 0, int $indent = 0, int $flags
                     $prefix,
                     $dumpAsMap ? Inline::dump($key, $flags).':' : '-',
                     $willBeInlined ? ' ' : "\n",
-                    $this->dump($value, $inline - 1, $willBeInlined ? 0 : $indent + $this->indentation, $flags)
+                    $this->doDump($value, $inline - 1, $willBeInlined ? 0 : $indent + $this->indentation, $flags, $nestingLevel + 1)
                 ).($willBeInlined ? "\n" : '');
             }
         }
@@ -134,7 +143,7 @@ public function dump(mixed $input, int $inline = 0, int $indent = 0, int $flags
         return $output;
     }
 
-    private function dumpTaggedValue(TaggedValue $value, int $inline, int $indent, int $flags, string $prefix): string
+    private function dumpTaggedValue(TaggedValue $value, int $inline, int $indent, int $flags, string $prefix, int $nestingLevel): string
     {
         $output = \sprintf('%s!%s', $prefix ? $prefix.' ' : '', $value->getTag());
 
@@ -150,10 +159,10 @@ private function dumpTaggedValue(TaggedValue $value, int $inline, int $indent, i
         }
 
         if ($inline - 1 <= 0 || null === $value->getValue() || \is_scalar($value->getValue())) {
-            return $output.' '.$this->dump($value->getValue(), $inline - 1, 0, $flags)."\n";
+            return $output.' '.$this->doDump($value->getValue(), $inline - 1, 0, $flags, $nestingLevel + 1)."\n";
         }
 
-        return $output."\n".$this->dump($value->getValue(), $inline - 1, $indent, $flags);
+        return $output."\n".$this->doDump($value->getValue(), $inline - 1, $indent, $flags, $nestingLevel + 1);
     }
 
     private function getBlockIndentationIndicator(string $value): string
diff --git a/src/Symfony/Component/Yaml/Inline.php b/src/Symfony/Component/Yaml/Inline.php
index 34ef66e654c5b..c310fe12b2829 100644
--- a/src/Symfony/Component/Yaml/Inline.php
+++ b/src/Symfony/Component/Yaml/Inline.php
@@ -100,7 +100,7 @@ public static function parse(string $value, int $flags = 0, array &$references =
      *
      * @throws DumpException When trying to dump PHP resource
      */
-    public static function dump(mixed $value, int $flags = 0): string
+    public static function dump(mixed $value, int $flags = 0, bool $rootLevel = false): string
     {
         switch (true) {
             case \is_resource($value):
@@ -138,7 +138,7 @@ public static function dump(mixed $value, int $flags = 0): string
             case \is_array($value):
                 return self::dumpArray($value, $flags);
             case null === $value:
-                return self::dumpNull($flags);
+                return self::dumpNull($flags, $rootLevel);
             case true === $value:
                 return 'true';
             case false === $value:
@@ -253,12 +253,16 @@ private static function dumpHashArray(array|\ArrayObject|\stdClass $value, int $
         return \sprintf('{ %s }', implode(', ', $output));
     }
 
-    private static function dumpNull(int $flags): string
+    private static function dumpNull(int $flags, bool $rootLevel = false): string
     {
         if (Yaml::DUMP_NULL_AS_TILDE & $flags) {
             return '~';
         }
 
+        if (Yaml::DUMP_NULL_AS_EMPTY & $flags && !$rootLevel) {
+            return '';
+        }
+
         return 'null';
     }
 
diff --git a/src/Symfony/Component/Yaml/Tests/DumperTest.php b/src/Symfony/Component/Yaml/Tests/DumperTest.php
index 24758b810445b..bb3ba62fa778a 100644
--- a/src/Symfony/Component/Yaml/Tests/DumperTest.php
+++ b/src/Symfony/Component/Yaml/Tests/DumperTest.php
@@ -216,6 +216,63 @@ public function testObjectSupportDisabledWithExceptions()
         $this->dumper->dump(['foo' => new A(), 'bar' => 1], 0, 0, Yaml::DUMP_EXCEPTION_ON_INVALID_TYPE);
     }
 
+    public function testDumpWithMultipleNullFlagsFormatsThrows()
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('The Yaml::DUMP_NULL_AS_EMPTY and Yaml::DUMP_NULL_AS_TILDE flags cannot be used together.');
+
+        $this->dumper->dump(['foo' => 'bar'], 0, 0, Yaml::DUMP_NULL_AS_EMPTY | Yaml::DUMP_NULL_AS_TILDE);
+    }
+
+    public function testDumpNullAsEmptyInExpandedMapping()
+    {
+        $expected = "qux:\n    foo: bar\n    baz: \n";
+
+        $this->assertSame($expected, $this->dumper->dump(['qux' => ['foo' => 'bar', 'baz' => null]], 2, flags: Yaml::DUMP_NULL_AS_EMPTY));
+    }
+
+    public function testDumpNullAsEmptyWithObject()
+    {
+        $class = new \stdClass();
+        $class->foo = 'bar';
+        $class->baz = null;
+
+        $this->assertSame("foo: bar\nbaz: \n", $this->dumper->dump($class, 2, flags: Yaml::DUMP_NULL_AS_EMPTY | Yaml::DUMP_OBJECT_AS_MAP));
+    }
+
+    public function testDumpNullAsEmptyDumpsWhenInInlineMapping()
+    {
+        $expected = "foo: \nqux: { foo: bar, baz:  }\n";
+
+        $this->assertSame($expected, $this->dumper->dump(['foo' => null, 'qux' => ['foo' => 'bar', 'baz' => null]], 1, flags: Yaml::DUMP_NULL_AS_EMPTY));
+    }
+
+    public function testDumpNullAsEmptyDumpsNestedMaps()
+    {
+        $expected = "foo: \nqux:\n    foo: bar\n    baz: \n";
+
+        $this->assertSame($expected, $this->dumper->dump(['foo' => null, 'qux' => ['foo' => 'bar', 'baz' => null]], 10, flags: Yaml::DUMP_NULL_AS_EMPTY));
+    }
+
+    public function testDumpNullAsEmptyInExpandedSequence()
+    {
+        $expected = "qux:\n    - foo\n    - \n    - bar\n";
+
+        $this->assertSame($expected, $this->dumper->dump(['qux' => ['foo', null, 'bar']], 2, flags: Yaml::DUMP_NULL_AS_EMPTY));
+    }
+
+    public function testDumpNullAsEmptyWhenInInlineSequence()
+    {
+        $expected = "foo: \nqux: [foo, , bar]\n";
+
+        $this->assertSame($expected, $this->dumper->dump(['foo' => null, 'qux' => ['foo', null, 'bar']], 1, flags: Yaml::DUMP_NULL_AS_EMPTY));
+    }
+
+    public function testDumpNullAsEmptyAtRoot()
+    {
+        $this->assertSame('null', $this->dumper->dump(null, 2, flags: Yaml::DUMP_NULL_AS_EMPTY));
+    }
+
     /**
      * @dataProvider getEscapeSequences
      */
diff --git a/src/Symfony/Component/Yaml/Tests/ParserTest.php b/src/Symfony/Component/Yaml/Tests/ParserTest.php
index fad946946b503..3850f041042f3 100644
--- a/src/Symfony/Component/Yaml/Tests/ParserTest.php
+++ b/src/Symfony/Component/Yaml/Tests/ParserTest.php
@@ -52,6 +52,33 @@ public function testTopLevelNull()
         $this->assertSameData($expected, $data);
     }
 
+    public function testEmptyValueInExpandedMappingIsSupported()
+    {
+        $yml = <<<'YAML'
+foo:
+    bar:
+    baz: qux
+YAML;
+
+        $data = $this->parser->parse($yml);
+        $expected = ['foo' => ['bar' => null, 'baz' => 'qux']];
+        $this->assertSameData($expected, $data);
+    }
+
+    public function testEmptyValueInExpandedSequenceIsSupported()
+    {
+        $yml = <<<'YAML'
+foo:
+    - bar
+    -
+    - baz
+YAML;
+
+        $data = $this->parser->parse($yml);
+        $expected = ['foo' => ['bar', null, 'baz']];
+        $this->assertSameData($expected, $data);
+    }
+
     public function testTaggedValueTopLevelNumber()
     {
         $yml = '!number 5';
diff --git a/src/Symfony/Component/Yaml/Yaml.php b/src/Symfony/Component/Yaml/Yaml.php
index 36b451988017a..03395b9770f3e 100644
--- a/src/Symfony/Component/Yaml/Yaml.php
+++ b/src/Symfony/Component/Yaml/Yaml.php
@@ -35,6 +35,7 @@ class Yaml
     public const DUMP_EMPTY_ARRAY_AS_SEQUENCE = 1024;
     public const DUMP_NULL_AS_TILDE = 2048;
     public const DUMP_NUMERIC_KEY_AS_STRING = 4096;
+    public const DUMP_NULL_AS_EMPTY = 8192;
 
     /**
      * Parses a YAML file into a PHP value.