feature symfony#60730 [JsonStreamer] Add include_null_properties option (mtarld)

This PR was merged into the 7.4 branch.

Discussion
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 [JsonStreamer] Add `include_null_properties` option

| Q             | A
| ------------- | ---
| Branch?       | 7.4
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Issues        |
| License       | MIT

A really common use case in APIs is to be able to skip properties with `null` value (for instance, this use case is required to make the JsonStreamer component working with API Platform).

~This PR adds the option `skip_null_properties` that allow to skip `null` properties during stream writing.~
~This PR skips properties with `nulln` values during stream writing.~
This PR adds the option `include_null_properties` that allow to encode `null` properties during stream writing.

This requires to define dynamic object prefixes (such as `''` and `','`). That's why the PHP generated code has been updated to merge as many prefixes as possible in raw strings and therefore yield a bit bigger chunks.

Commits
-------

d662f85  [JsonStreamer] Add `include_null_properties` option

Author: nicolas-grekas

src/Symfony/Component/JsonStreamer/CHANGELOG.md

@@ -6,6 +6,7 @@ CHANGELOG
 
  * Remove `nikic/php-parser` dependency
  * Add `_current_object` to the context passed to value transformers during write operations
+ * Add `include_null_properties` option to encode the properties with `null` value
 
 7.3
 ---

src/Symfony/Component/JsonStreamer/JsonStreamWriter.php

@@ -29,7 +29,10 @@
 /**
  * @author Mathias Arlaud <mathias.arlaud@gmail.com>
  *
- * @implements StreamWriterInterface<array<string, mixed>>
+ * @implements StreamWriterInterface<array{
+ *     include_null_properties?: bool,
+ *     ...<string, mixed>,
+ * }>
  *
  * @experimental
  */

src/Symfony/Component/JsonStreamer/Tests/Fixtures/Model/DummyWithDollarNamedProperties.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Symfony\Component\JsonStreamer\Tests\Fixtures\Model;
+
+use Symfony\Component\JsonStreamer\Attribute\StreamedName;
+
+class DummyWithDollarNamedProperties
+{
+    #[StreamedName('$foo')]
+    public bool $foo = true;
+
+    #[StreamedName('{$foo->bar}')]
+    public bool $bar = true;
+}