Python: Pass the env parameter into handlers (#1610)

This adds a relaxed_call function taken from
pyodide/pyodide#4392
and uses it to pass the env argument to the fetch/test handlers

samples/pyodide-secret/config.capnp

@@ -0,0 +1,37 @@
+using Workerd = import "/workerd/workerd.capnp";
+
+const config :Workerd.Config = (
+  services = [
+    (name = "main", worker = .mainWorker),
+  ],
+
+  sockets = [
+    # Serve HTTP on port 8080.
+    ( name = "http",
+      address = "*:8080",
+      http = (),
+      service = "main"
+    ),
+  ],
+  autogates = [
+    # Pyodide is included as a builtin wasm module so it requires the
+    # corresponding autogate flag.
+    "workerd-autogate-builtin-wasm-modules",
+  ]
+);
+
+const mainWorker :Workerd.Worker = (
+  modules = [
+    (name = "worker.py", pythonModule = embed "./worker.py"),
+  ],
+  compatibilityDate = "2023-12-18",
+  compatibilityFlags = ["experimental"],
+  bindings = [
+    (
+      name = "secret",
+      text = "thisisasecret"
+    ),
+  ],
+  # Learn more about compatibility dates at:
+  # https://developers.cloudflare.com/workers/platform/compatibility-dates/
+);

samples/pyodide-secret/worker.py

@@ -0,0 +1,11 @@
+from js import Response
+
+
+def fetch(request, env):
+    print(env.secret)
+    return Response.new("hello world")
+
+
+def test(ctx, env):
+    print(env.secret)
+    print("Hi there, this is a test")

src/pyodide/internal/relaxed_call.py

@@ -0,0 +1,88 @@
+"""
+Allow calling functions with more arguments than they want
+
+Copied from
+https://github.com/pyodide/pyodide/pull/4392/
+"""
+
+from collections.abc import Callable
+from functools import lru_cache, wraps
+from inspect import Parameter, Signature, signature
+from typing import Any, ParamSpec, TypeVar
+
+
+def _relaxed_call_sig(func: Callable[..., Any]) -> Signature | None:
+    try:
+        sig = signature(func)
+    except (TypeError, ValueError):
+        return None
+    new_params = list(sig.parameters.values())
+    idx: int | None = -1
+    for idx, param in enumerate(new_params):
+        if param.kind in (Parameter.KEYWORD_ONLY, Parameter.VAR_KEYWORD):
+            break
+        if param.kind == Parameter.VAR_POSITIONAL:
+            idx = None
+            break
+    else:
+        idx += 1
+    if idx is not None:
+        new_params.insert(idx, Parameter("__var_positional", Parameter.VAR_POSITIONAL))
+
+    for param in new_params:
+        if param.kind == Parameter.VAR_KEYWORD:
+            break
+    else:
+        new_params.append(Parameter("__var_keyword", Parameter.VAR_KEYWORD))
+    new_sig = sig.replace(parameters=new_params)
+    return new_sig
+
+
+@lru_cache
+def _relaxed_call_sig_cached(func: Callable[..., Any]) -> Signature | None:
+    return _relaxed_call_sig(func)
+
+
+def _do_call(
+    func: Callable[..., Any], sig: Signature, args: Any, kwargs: dict[str, Any]
+) -> Any:
+    bound = sig.bind(*args, **kwargs)
+    bound.arguments.pop("__var_positional", None)
+    bound.arguments.pop("__var_keyword", None)
+    return func(*bound.args, **bound.kwargs)
+
+
+Param = ParamSpec("Param")
+Param2 = ParamSpec("Param2")
+RetType = TypeVar("RetType")
+
+
+def relaxed_wrap(func: Callable[Param, RetType]) -> Callable[..., RetType]:
+    """Decorator which creates a function that ignores extra arguments
+
+    If extra positional or keyword arguments are provided they will be
+    discarded.
+    """
+    sig = _relaxed_call_sig(func)
+    if sig is None:
+        raise TypeError("Cannot wrap function")
+    else:
+        sig2 = sig
+
+    @wraps(func)
+    def wrapper(*args: Param.args, **kwargs: Param.kwargs) -> RetType:
+        return _do_call(func, sig2, args, kwargs)
+
+    return wrapper
+
+
+def relaxed_call(func: Callable[..., RetType], *args: Any, **kwargs: Any) -> RetType:
+    """Call the function ignoring extra arguments
+
+    If extra positional or keyword arguments are provided they will be
+    discarded.
+    """
+    sig = _relaxed_call_sig_cached(func)
+    if sig is None:
+        return func(*args, **kwargs)
+    return _do_call(func, sig, args, kwargs)

src/pyodide/python-entrypoint-helper.js

@@ -9,7 +9,7 @@ import { default as MetadataReader } from "pyodide-internal:runtime-generated/me
 function initializePackageIndex(pyodide) {
   if (!lockfile.packages) {
     throw new Error(
-      "Loaded pyodide lock file does not contain the expected key 'packages'."
+      "Loaded pyodide lock file does not contain the expected key 'packages'.",
     );
   }
   const API = pyodide._api;
@@ -101,6 +101,15 @@ async function setupPackages(pyodide) {
   const isWorkerd = MetadataReader.isWorkerd();
 
   initializePackageIndex(pyodide);
+  {
+    const mod = await import("pyodide-internal:relaxed_call.py");
+    pyodide.FS.writeFile(
+      "/lib/python3.11/site-packages/relaxed_call.py",
+      new Uint8Array(mod.default),
+      { canOwn: true },
+    );
+  }
+
   const requirements = MetadataReader.getRequirements();
   const pythonRequirements = isWorkerd ? requirements : requirements.filter(req => !EMBEDDED_PYTHON_PACKAGES.has(req));
 
@@ -122,16 +131,16 @@ async function setupPackages(pyodide) {
     pyodide.FS.writeFile(
       "/lib/python3.11/site-packages/aiohttp_fetch_patch.py",
       new Uint8Array(mod.default),
-      { canOwn: true }
+      { canOwn: true },
     );
     pyodide.pyimport("aiohttp_fetch_patch");
   }
-  if (requirements.some(req => req.startsWith("fastapi"))) {
+  if (requirements.some((req) => req.startsWith("fastapi"))) {
     const mod = await import("pyodide-internal:asgi.py");
     pyodide.FS.writeFile(
       "/lib/python3.11/site-packages/asgi.py",
       new Uint8Array(mod.default),
-      { canOwn: true }
+      { canOwn: true },
     );
   }
   let mainModuleName = MetadataReader.getMainModule();
@@ -142,28 +151,30 @@ async function setupPackages(pyodide) {
 }
 
 let mainModulePromise;
-function getMainModule() {
+function getPyodide() {
   if (mainModulePromise !== undefined) {
     return mainModulePromise;
   }
   mainModulePromise = (async function() {
     // TODO: investigate whether it is possible to run part of loadPyodide in top level scope
     // When we do it in top level scope we seem to get a broken file system.
     const pyodide = await loadPyodide();
-    return await setupPackages(pyodide);
+    const mainModule = await setupPackages(pyodide);
+    const relaxed_call = pyodide.pyimport("relaxed_call").relaxed_call;
+    return { mainModule, relaxed_call };
   })();
   return mainModulePromise;
 }
 
 export default {
-  async fetch(request, env) {
-    const mainModule = await getMainModule();
-    return await mainModule.fetch(request);
+  async fetch(request, env, ctx) {
+    const { relaxed_call, mainModule } = await getPyodide();
+    return await relaxed_call(mainModule.fetch, request, env, ctx);
   },
-  async test() {
+  async test(ctrl, env, ctx) {
     try {
-      const mainModule = await getMainModule();
-      return await mainModule.test();
+      const { relaxed_call, mainModule } = await getPyodide();
+      return await relaxed_call(mainModule.test, ctrl, env, ctx);
     } catch (e) {
       console.warn(e);
     }