Marshmallow field validation for an empty text field

marshmallow.ipynb

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   "cell_type": "code",
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   "source": [
    "import itertools\n",
    "\n",
    "from marshmallow import Schema, fields"
   ]
  },
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   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
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     "text": [
      "(True, undefined, None)\n",
      "(True, None, None)\n",
      "(True, '', None)\n",
      "(True, 'some string', None)\n",
      "(False, undefined, None)\n",
      "(False, None, None)\n",
      "(False, '', None)\n",
      "(False, 'some string', None)\n"
     ]
    }
   ],
   "source": [
    "def test(**kwargs):\n",
    "    class TestSchema(Schema):\n",
    "        name = fields.Str(**kwargs)\n",
    "    s = TestSchema()\n",
    "    return s.load({'name': None})\n",
    "\n",
    "class Undefined:\n",
    "    def __repr__(self):\n",
    "        return 'undefined'\n",
    "\n",
    "undefined = Undefined()\n",
    "required = [True, False]\n",
    "default = missing = [undefined, None, '', 'some string']\n",
    "\n",
    "for p in itertools.product(required, default, missing):\n",
    "    kwargs = dict(zip(['required', 'default', 'missing'], p))\n",
    "    kwargs = {k: v for k, v in kwargs.items() if v is not undefined}\n",
    "    if not test(**kwargs).errors:\n",
    "        print(p)\n"
   ]
  }
 ],
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