feat: add error check to getHeaderLine()

Author: kenjis

system/HTTP/Message.php

@@ -11,6 +11,8 @@
 
 namespace CodeIgniter\HTTP;
 
+use InvalidArgumentException;
+
 /**
  * An HTTP message
  *
@@ -112,6 +114,13 @@ public function hasHeader(string $name): bool
      */
     public function getHeaderLine(string $name): string
     {
+        if ($this->hasMultipleHeaders($name)) {
+            throw new InvalidArgumentException(
+                'The header "' . $name . '" already has multiple headers.'
+                . ' You cannot use getHeaderLine().'
+            );
+        }
+
         $origName = $this->getHeaderName($name);
 
         if (! array_key_exists($origName, $this->headers)) {

tests/system/HTTP/MessageTest.php

@@ -355,4 +355,23 @@ public function testAppendHeaderWithMultipleHeaders(): void
 
         $this->message->appendHeader('Set-Cookie', 'HttpOnly');
     }
+
+    public function testGetHeaderLineWithMultipleHeaders(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage(
+            'The header "Set-Cookie" already has multiple headers. You cannot use getHeaderLine().'
+        );
+
+        $this->message->addHeader(
+            'Set-Cookie',
+            'logged_in=no; Path=/'
+        );
+        $this->message->addHeader(
+            'Set-Cookie',
+            'sessid=123456; Path=/'
+        );
+
+        $this->message->getHeaderLine('Set-Cookie');
+    }
 }