Add autogate that forces on external python bundle loading

So we can roll it out gradually

Author: hoodmane

Diff for: src/workerd/api/pyodide/pyodide.h

@@ -425,7 +425,8 @@ bool hasPythonModules(capnp::List<server::config::Worker::Module>::Reader module
 template <class Registry>
 void registerPyodideModules(Registry& registry, auto featureFlags) {
   // We add `pyodide:` packages here including python-entrypoint-helper.js.
-  if (!featureFlags.getPythonExternalBundle()) {
+  if (!featureFlags.getPythonExternalBundle() &&
+      !util::Autogate::isEnabled(util::AutogateKey::PYTHON_EXTERNAL_BUNDLE)) {
     registry.addBuiltinBundle(PYODIDE_BUNDLE, kj::none);
   }
   registry.template addBuiltinModule<PackagesTarReader>(
@@ -435,7 +436,8 @@ void registerPyodideModules(Registry& registry, auto featureFlags) {
 kj::Own<jsg::modules::ModuleBundle> getInternalPyodideModuleBundle(auto featureFlags) {
   jsg::modules::ModuleBundle::BuiltinBuilder builder(
       jsg::modules::ModuleBundle::BuiltinBuilder::Type::BUILTIN_ONLY);
-  if (!featureFlags.getPythonExternalBundle()) {
+  if (!featureFlags.getPythonExternalBundle() &&
+      !util::Autogate::isEnabled(util::AutogateKey::PYTHON_EXTERNAL_BUNDLE)) {
     jsg::modules::ModuleBundle::getBuiltInBundleFromCapnp(builder, PYODIDE_BUNDLE);
   }
   return builder.finish();
@@ -444,7 +446,8 @@ kj::Own<jsg::modules::ModuleBundle> getInternalPyodideModuleBundle(auto featureF
 kj::Own<jsg::modules::ModuleBundle> getExternalPyodideModuleBundle(auto featureFlags) {
   jsg::modules::ModuleBundle::BuiltinBuilder builder(
       jsg::modules::ModuleBundle::BuiltinBuilder::Type::BUILTIN);
-  if (!featureFlags.getPythonExternalBundle()) {
+  if (!featureFlags.getPythonExternalBundle() &&
+      !util::Autogate::isEnabled(util::AutogateKey::PYTHON_EXTERNAL_BUNDLE)) {
     jsg::modules::ModuleBundle::getBuiltInBundleFromCapnp(builder, PYODIDE_BUNDLE);
   }
   return builder.finish();

Diff for: src/workerd/server/workerd-api.c++

@@ -511,7 +511,8 @@ void WorkerdApi::compileModules(jsg::Lock& lockParam,
       KJ_REQUIRE(featureFlags.getPythonWorkers(),
           "The python_workers compatibility flag is required to use Python.");
       // Inject Pyodide bundle
-      if (featureFlags.getPythonExternalBundle()) {
+      if (featureFlags.getPythonExternalBundle() ||
+          util::Autogate::isEnabled(util::AutogateKey::PYTHON_EXTERNAL_BUNDLE)) {
         auto pythonRelease = KJ_ASSERT_NONNULL(getPythonSnapshotRelease(featureFlags));
         auto version = getPythonBundleName(pythonRelease);
         auto bundle = KJ_ASSERT_NONNULL(

Diff for: src/workerd/util/autogate.c++

@@ -17,6 +17,8 @@ kj::StringPtr KJ_STRINGIFY(AutogateKey key) {
   switch (key) {
     case AutogateKey::TEST_WORKERD:
       return "test-workerd"_kj;
+    case AutogateKey::PYTHON_EXTERNAL_BUNDLE:
+      return "python-external-bundle"_kj;
     case AutogateKey::NumOfKeys:
       KJ_FAIL_ASSERT("NumOfKeys should not be used in getName");
   }

Diff for: src/workerd/util/autogate.h

@@ -14,6 +14,7 @@ namespace workerd::util {
 // Workerd-specific list of autogate keys (can also be used in internal repo).
 enum class AutogateKey {
   TEST_WORKERD,
+  PYTHON_EXTERNAL_BUNDLE,
   NumOfKeys  // Reserved for iteration.
 };