fix: [Validation] JSON data may cause "Array to string conversion" error

system/Validation/Validation.php

@@ -328,7 +328,9 @@ protected function processRules(
  if ($passed === false) {
  // if the $value is an array, convert it to as string representation
  if (is_array($value)) {
- $value = '[' . implode(', ', $value) . ']';
+ $value = $this->isStringList($value)
+ ? '[' . implode(', ', $value) . ']'
+ : json_encode($value);
  } elseif (is_object($value)) {
  $value = json_encode($value);
  }
@@ -351,6 +353,32 @@ protected function processRules(
  return true;
  }
 
+ /**
+ * Is the array a string list `list<string>`?
+ */
+ private function isStringList(array $array): bool
+ {
+ $expectedKey = 0;
+
+ foreach ($array as $key => $val) {
+ // Note: also covers PHP array key conversion, e.g. '5' and 5.1 both become 5
+ if (! is_int($key)) {
+ return false;
+ }
+
+ if ($key !== $expectedKey) {
+ return false;
+ }
+ $expectedKey++;
+
+ if (! is_string($val)) {
+ return false;
+ }
+ }
+
+ return true;
+ }
+
  /**
  * Takes a Request object and grabs the input data to use from its
  * array values.

tests/_support/Validation/TestRules.php

@@ -32,4 +32,9 @@ public function check_object_rule(object $value, ?string $fields, array $data =
 
  return $find;
  }
+
+ public function array_count($value, $count): bool
+ {
+ return is_array($value) && count($value) === (int) $count;
+ }
 }

tests/system/Validation/ValidationTest.php

@@ -641,6 +641,42 @@ public function testJsonInput(): void
  unset($_SERVER['CONTENT_TYPE']);
  }
 
+ /**
+ * @see https://github.com/codeigniter4/CodeIgniter4/issues/6466
+ */
+ public function testJsonInputObjectArray(): void
+ {
+ $json = <<<'EOL'
+ {
+ "p": [
+ {
+ "id": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+ }
+ ]
+ }
+ EOL;
+
+ $_SERVER['CONTENT_TYPE'] = 'application/json';
+
+ $config = new App();
+ $config->baseURL = 'http://example.com/';
+
+ $request = new IncomingRequest($config, new URI(), $json, new UserAgent());
+
+ $rules = [
+ 'p' => 'required|array_count[2]',
+ ];
+ $validated = $this->validation
+ ->withRequest($request->withMethod('patch'))
+ ->setRules($rules)
+ ->run();
+
+ $this->assertFalse($validated);
+ $this->assertSame(['p' => 'Validation.array_count'], $this->validation->getErrors());
+
+ unset($_SERVER['CONTENT_TYPE']);
+ }
+
  public function testHasRule(): void
  {
  $this->validation->setRuleGroup('groupA');