bug #29741 [VarExporter] fix exporting array indexes (xabbuh)

This PR was merged into the 4.2 branch.

Discussion
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[VarExporter] fix exporting array indexes

| Q             | A
| ------------- | ---
| Branch?       | 4.2
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #29715
| License       | MIT
| Doc PR        |

Commits
-------

3c936f447b [VarExporter] fix exporting array indexes

src/Symfony/Component/VarExporter/Internal/Exporter.php

@@ -232,7 +232,7 @@ class Exporter
                 if (!\is_int($k) || 1 !== $k - $j) {
                     $code .= self::export($k, $subIndent).' => ';
                 }
-                if (\is_int($k)) {
+                if (\is_int($k) && $k > $j) {
                     $j = $k;
                 }
                 $code .= self::export($v, $subIndent).",\n";

src/Symfony/Component/VarExporter/Tests/Fixtures/partially-indexed-array.php

@@ -0,0 +1,8 @@
+<?php
+
+return [
+    5 => true,
+    1 => true,
+    2 => true,
+    true,
+];

src/Symfony/Component/VarExporter/Tests/VarExporterTest.php

@@ -112,6 +112,7 @@ class VarExporterTest extends TestCase
 
         yield array('bool', true, true);
         yield array('simple-array', array(123, array('abc')), true);
+        yield array('partially-indexed-array', array(5 => true, 1 => true, 2 => true, 6 => true), true);
         yield array('datetime', \DateTime::createFromFormat('U', 0));
 
         $value = new \ArrayObject();