fix: Add libs/python3.lib to libpython target for SABI builds on Windows

CHANGELOG.md

@@ -95,6 +95,9 @@ Other changes:
   ([2169](https://github.com/bazelbuild/rules_python/issues/2169)).
 * (workspace) Corrected protobuf's name to com_google_protobuf, the name is
   hardcoded in Bazel, WORKSPACE mode.
+* (repositories): Add libs/python3.lib and pythonXY.dll to the `libpython` target
+  defined by a repository template. This enables stable ABI builds of Python extensions
+  on Windows (by defining Py_LIMITED_API).
 
 {#v0-0-0-added}
 ### Added

python/private/hermetic_runtime_repo_setup.bzl

@@ -89,6 +89,14 @@ def define_hermetic_runtime_toolchain_impl(
         }),
         system_provided = True,
     )
+    cc_import(
+        name = "abi3_interface",
+        interface_library = select({
+            _IS_FREETHREADED: "libs/python3t.lib",
+            "//conditions:default": "libs/python3.lib",
+        }),
+        system_provided = True,
+    )
 
     native.filegroup(
         name = "includes",
@@ -97,7 +105,7 @@ def define_hermetic_runtime_toolchain_impl(
     cc_library(
         name = "python_headers",
         deps = select({
-            "@bazel_tools//src/conditions:windows": [":interface"],
+            "@bazel_tools//src/conditions:windows": [":interface", ":abi3_interface"],
             "//conditions:default": None,
         }),
         hdrs = [":includes"],
@@ -156,15 +164,22 @@ def define_hermetic_runtime_toolchain_impl(
                 "lib/libpython{major}.{minor}t.dylib".format(**version_dict),
             ],
             ":is_freethreaded_windows": [
-                "python3.dll",
+                "python3t.dll",
+                "python{major}{minor}t.dll".format(**version_dict),
                 "libs/python{major}{minor}t.lib".format(**version_dict),
+                "libs/python3t.lib",
             ],
             "@platforms//os:linux": [
                 "lib/libpython{major}.{minor}.so".format(**version_dict),
                 "lib/libpython{major}.{minor}.so.1.0".format(**version_dict),
             ],
             "@platforms//os:macos": ["lib/libpython{major}.{minor}.dylib".format(**version_dict)],
-            "@platforms//os:windows": ["python3.dll", "libs/python{major}{minor}.lib".format(**version_dict)],
+            "@platforms//os:windows": [
+                "python3.dll",
+                "python{major}{minor}.dll".format(**version_dict),
+                "libs/python{major}{minor}.lib".format(**version_dict),
+                "libs/python3.lib",
+            ],
         }),
     )
 

tests/cc/current_py_cc_libs/BUILD.bazel

@@ -33,3 +33,21 @@ cc_test(
         "@rules_python//python/cc:current_py_cc_libs",
     ],
 )
+
+# This is technically a headers test, but since the pyconfig.h header
+# designates the appropriate lib to link on Win+MSVC, this test verifies that
+# the expected Windows libraries are all present in the expected location.
+# Since we define the Py_LIMITED_API macro, we expect the linker to go search
+# for libs/python3.lib.
+# buildifier: disable=native-cc
+cc_test(
+    name = "python_libs_linking_windows_test",
+    srcs = ["python_libs_linking_test.cc"],
+    defines = ["Py_LIMITED_API=0x030A0000"],
+    env = {"HELLO": "world"},
+    target_compatible_with = ["@platforms//os:windows"],
+    deps = [
+        "@rules_python//python/cc:current_py_cc_headers",
+        "@rules_python//python/cc:current_py_cc_libs",
+    ],
+)

tests/cc/current_py_cc_libs/python_libs_linking_test.cc

@@ -1,8 +1,11 @@
 #include <Python.h>
 
 int main(int argc, char** argv) {
+
+  // PyObject *s = PyUnicode_FromString(argv[0]);
   // Early return to prevent the broken code below from running.
   if (argc >= 1) {
+    // printf("%d\n", (int)s->ob_refcnt);
     return 0;
   }
 
@@ -12,7 +15,7 @@ int main(int argc, char** argv) {
   // To make it actually run, more custom initialization is necessary.
   // See https://docs.python.org/3/c-api/intro.html#embedding-python
   Py_Initialize();
-  PyRun_SimpleString("print('Hello, world')\n");
+  Py_BytesMain(argc, argv);
   Py_Finalize();
   return 0;
 }