Fixup importing built-ins from module "subdirectories"

src/workerd/api/tests/module-test.js

@@ -0,0 +1,11 @@
+import * as assert from 'a/b/c';
+import * as assert3 from 'node:assert';
+
+export const abortcontroller = {
+  async test() {
+    const assert2 = await import('a/b/c');
+    if (assert !== assert2 && assert !== assert3) {
+      throw new Error('bad things happened');
+    }
+  }
+};

src/workerd/api/tests/module-test.wd-test

@@ -0,0 +1,17 @@
+using Workerd = import "/workerd/workerd.capnp";
+
+const unitTests :Workerd.Config = (
+  services = [
+    ( name = "module-test",
+      worker = (
+        modules = [
+          (name = "worker", esModule = embed "module-test.js"),
+          (name = "a/b/c",
+           esModule = "import * as assert from 'node:assert'; await import('node:buffer'); export default assert;"),
+        ],
+        compatibilityDate = "2023-01-15",
+        compatibilityFlags = ["nodejs_compat"]
+      )
+    ),
+  ],
+);

src/workerd/jsg/modules.c++

@@ -65,9 +65,18 @@ v8::MaybeLocal<v8::Module> resolveCallback(v8::Local<v8::Context> context,
     bool internalOnly = ref.type == ModuleRegistry::Type::BUILTIN ||
                         ref.type == ModuleRegistry::Type::INTERNAL;
 
-    kj::Path targetPath = !internalOnly ?
-        ref.specifier.parent().eval(spec) :
-        kj::Path::parse(spec);
+    kj::Path targetPath = ([&] {
+      // If the specifier begins with one of our known prefixes, let's not resolve
+      // it against the referrer.
+      auto spec = kj::str(specifier);
+      if (internalOnly ||
+          spec.startsWith("node:") ||
+          spec.startsWith("cloudflare:") ||
+          spec.startsWith("workerd:")) {
+        return kj::Path::parse(spec);
+      }
+      return ref.specifier.parent().eval(spec);
+    })();
 
     KJ_IF_SOME(resolved, registry->resolve(js, targetPath, ref.specifier,
         internalOnly ?
@@ -245,7 +254,16 @@ v8::Local<v8::Value> CommonJsModuleContext::require(jsg::Lock& js, kj::String sp
   auto modulesForResolveCallback = getModulesForResolveCallback(js.v8Isolate);
   KJ_REQUIRE(modulesForResolveCallback != nullptr, "didn't expect resolveCallback() now");
 
-  kj::Path targetPath = path.parent().eval(specifier);
+  kj::Path targetPath = ([&] {
+    // If the specifier begins with one of our known prefixes, let's not resolve
+    // it against the referrer.
+    if (specifier.startsWith("node:") ||
+        specifier.startsWith("cloudflare:") ||
+        specifier.startsWith("workerd:")) {
+      return kj::Path::parse(specifier);
+    }
+    return path.parent().eval(specifier);
+  })();
 
   // require() is only exposed to worker bundle modules so the resolve here is only
   // permitted to require worker bundle or built-in modules. Internal modules are
@@ -587,7 +605,16 @@ v8::Local<v8::Value> NodeJsModuleContext::require(jsg::Lock& js, kj::String spec
   auto modulesForResolveCallback = jsg::getModulesForResolveCallback(js.v8Isolate);
   KJ_REQUIRE(modulesForResolveCallback != nullptr, "didn't expect resolveCallback() now");
 
-  kj::Path targetPath = path.parent().eval(specifier);
+  kj::Path targetPath = ([&] {
+    // If the specifier begins with one of our known prefixes, let's not resolve
+    // it against the referrer.
+    if (specifier.startsWith("node:") ||
+        specifier.startsWith("cloudflare:") ||
+        specifier.startsWith("workerd:")) {
+      return kj::Path::parse(specifier);
+    }
+    return path.parent().eval(specifier);
+  })();
 
   // require() is only exposed to worker bundle modules so the resolve here is only
   // permitted to require worker bundle or built-in modules. Internal modules are

src/workerd/jsg/modules.h

@@ -825,9 +825,17 @@ v8::MaybeLocal<v8::Promise> dynamicImportCallback(v8::Local<v8::Context> context
   })();
 
   auto maybeSpecifierPath = ([&]() -> kj::Maybe<kj::Path> {
+    // If the specifier begins with one of our known prefixes, let's not resolve
+    // it against the referrer.
+    auto spec = kj::str(specifier);
+    if (spec.startsWith("node:") ||
+        spec.startsWith("cloudflare:") ||
+        spec.startsWith("workerd:")) {
+      return kj::Path::parse(spec);
+    }
     KJ_IF_SOME(referrerPath, maybeReferrerPath) {
       try {
-        return referrerPath.parent().eval(kj::str(specifier));
+        return referrerPath.parent().eval(spec);
       } catch (kj::Exception& ex) {
         return kj::none;
       }