Using Wrapt to alter a method signature

wrapt_type_munging_example.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "98e1a19f",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Collecting wrapt\n",
      "  Using cached wrapt-1.14.0-cp39-cp39-macosx_10_9_x86_64.whl (35 kB)\n",
      "Installing collected packages: wrapt\n",
      "Successfully installed wrapt-1.14.0\n",
      "\u001b[33mWARNING: You are using pip version 21.2.4; however, version 22.0.4 is available.\n",
      "You should consider upgrading via the '/Users/lucaswiman/personal/private-stuff/work/20220402--etl-blog-post/.venv/bin/python -m pip install --upgrade pip' command.\u001b[0m\n"
     ]
    }
   ],
   "source": [
    "!pip install wrapt"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "881d2fc1",
   "metadata": {},
   "outputs": [],
   "source": [
    "import wrapt\n",
    "import uuid\n",
    "import inspect\n",
    "from typing import *\n",
    "\n",
    "def get_argspec_including_annotations(\n",
    "    func: Callable,\n",
    "    added_annotations: Dict[str, type],\n",
    "    removed_args: Sequence[str] = (),\n",
    "    validate=False,\n",
    ") -> inspect.FullArgSpec:\n",
    "    signature = inspect.signature(func)\n",
    "    spec = inspect.getfullargspec(func)._asdict()\n",
    "    for name, annotation in added_annotations.items():\n",
    "        if name not in signature.parameters:\n",
    "            spec[\"kwonlyargs\"].append(name)\n",
    "        spec[\"annotations\"][name] = annotation\n",
    "    for name in removed_args:\n",
    "        if name in signature.parameters:\n",
    "            if name in spec[\"args\"]:\n",
    "                spec[\"args\"].remove(name)\n",
    "            if name in spec[\"kwonlyargs\"]:\n",
    "                spec[\"kwonlyargs\"].remove(name)\n",
    "            spec[\"annotations\"].pop(name, None)\n",
    "\n",
    "    return inspect.FullArgSpec(**spec)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "76a5f833",
   "metadata": {},
   "outputs": [],
   "source": [
    "def get_fastapi_method_argspec(func: Callable) -> inspect.ArgSpec:\n",
    "    return get_argspec_including_annotations(func, {\"client_token\": uuid.UUID}, [\"job_context\"])\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "id": "39d7e9a3",
   "metadata": {},
   "outputs": [],
   "source": [
    "@wrapt.decorator(adapter=wrapt.adapter_factory(get_fastapi_method_argspec))\n",
    "def munge_types(wrapped, instance, args, kwargs):\n",
    "    client_token = kwargs.pop(\"client_token\", None)\n",
    "    if not client_token:\n",
    "        client_token = uuid.uuid4()\n",
    "    job_context = {\"client_token\": client_token}\n",
    "    signature = inspect.signature(wrapped)\n",
    "    bound = signature.bind(*args, **kwargs)\n",
    "    bound.apply_defaults()\n",
    "    \n",
    "    # Note: job_context can be positional or kwarg and it will do the right thing\n",
    "    bound.arguments[\"job_context\"] = job_context\n",
    "    print(f\"calling with {bound.args=}, {bound.kwargs=}\")\n",
    "    return wrapped(*bound.args, **bound.kwargs)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "id": "c10658d6",
   "metadata": {},
   "outputs": [],
   "source": [
    "@munge_types\n",
    "def add(\n",
    "    x: int,\n",
    "    *,\n",
    "    y: int = 1,\n",
    "    job_context: Optional[\"JobContext\"] = None,\n",
    ") -> int:\n",
    "    print(f\"got {job_context=} for {x=}\")\n",
    "    return x + 1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "id": "47a9e0f0",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "calling with bound.args=(1,), bound.kwargs={'y': 2, 'job_context': {'client_token': UUID('2f2a15e5-9b9d-4b2e-a434-46d9c3e2e9ae')}}\n",
      "got job_context={'client_token': UUID('2f2a15e5-9b9d-4b2e-a434-46d9c3e2e9ae')} for x=1\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "2"
      ]
     },
     "execution_count": 32,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "add(1, y=2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "id": "4959bf47",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "calling with bound.args=(1,), bound.kwargs={'y': 1, 'job_context': {'client_token': UUID('84476126-2c91-4f31-a6c0-b5924816d172')}}\n",
      "got job_context={'client_token': UUID('84476126-2c91-4f31-a6c0-b5924816d172')} for x=1\n"
     ]
    },
    {
     "data": {
      "text/plain": [
       "2"
      ]
     },
     "execution_count": 33,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "add(1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "id": "f8f5b4d4",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'x': int,\n",
       " 'y': int,\n",
       " 'job_context': typing.Optional[ForwardRef('JobContext')],\n",
       " 'return': int}"
      ]
     },
     "execution_count": 35,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "add.__annotations__"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "id": "4f3786f7",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "FullArgSpec(args=['x'], varargs=None, varkw=None, defaults=None, kwonlyargs=['y', 'client_token'], kwonlydefaults={'y': 1}, annotations={'return': <class 'int'>, 'x': <class 'int'>, 'y': <class 'int'>, 'client_token': <class 'uuid.UUID'>})"
      ]
     },
     "execution_count": 36,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "inspect.getfullargspec(add)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "f56442cb",
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3 (ipykernel)",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.9.1"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 5
}