fix header encode run into iconv Unknown error (7)

src/Header/HeaderWrap.php

@@ -116,7 +116,21 @@ public static function mimeDecodeValue($value)
      */
     public static function canBeEncoded($value)
     {
-        $encoded = iconv_mime_encode('x-test', $value, ['scheme' => 'Q']);
+        // avoid any wrapping by specifying line length long enough
+        // "test" -> 4
+        // "x-test: =?ISO-8859-1?B?dGVzdA==?=" -> 33
+        //  8       +2          +3         +3  -> 16
+        $charset = 'UTF-8';
+        $line_length = strlen($value) * 4 + strlen($charset) + 16;
+
+        $preferences = [
+            'scheme' => 'Q',
+            'input-charset' => $charset,
+            'output-charset' => $charset,
+            'line-length' => $line_length,
+        ];
+
+        $encoded = iconv_mime_encode('x-test', $value, $preferences);
 
         return (false !== $encoded);
     }

test/Header/HeaderWrapTest.php

@@ -9,6 +9,7 @@
 
 namespace ZendTest\Mail\Header;
 
+use Zend\Mail\Header\GenericHeader;
 use Zend\Mail\Header\HeaderWrap;
 
 /**
@@ -70,4 +71,24 @@ public function testMimeDecoding()
 
         $this->assertEquals($expected, $decoded);
     }
+
+    /**
+     * Test that fails with HeaderWrap::canBeEncoded at lowest level:
+     *   iconv_mime_encode(): Unknown error (7)
+     *
+     * which can be triggered as:
+     *   $header = new GenericHeader($name, $value);
+     */
+    public function testCanBeEncoded()
+    {
+        $name = 'Subject';
+        $value = "[#77675] New Issue:xxxxxxxxx xxxxxxx xxxxxxxx xxxxxxxxxxxxx xxxxxxxxxx xxxxxxxx, tähtaeg xx.xx, xxxx";
+        $encoded = "Subject: =?UTF-8?Q?[#77675]=20New=20Issue:xxxxxxxxx=20xxxxxxx=20xxxxxxxx=20?=\r\n =?UTF-8?Q?xxxxxxxxxxxxx=20xxxxxxxxxx=20xxxxxxxx,=20t=C3=A4htaeg=20xx.xx,=20xxxx?=";
+        $res = HeaderWrap::canBeEncoded($value);
+        $this->assertTrue($res);
+
+        $header = new GenericHeader($name, $value);
+        $res = $header->toString();
+        $this->assertEquals($encoded, $res);
+    }
 }