make multiarch origin a fallback

Author: rickeylev

python/private/get_local_runtime_info.py

@@ -35,7 +35,15 @@
     # of settings.
     # https://stackoverflow.com/questions/47423246/get-pythons-lib-path
     # For now, it seems LIBDIR has what is needed, so just use that.
+    # See also: MULTIARCH
     "LIBDIR",
+    # On Debian, with multiarch enabled, prior to Python 3.10, `LIBDIR` didn't
+    # tell the location of the libs, just the base directory. The `MULTIARCH`
+    # sysconfig variable tells the subdirectory within it with the libs.
+    # See:
+    # https://wiki.debian.org/Python/MultiArch
+    # https://git.launchpad.net/ubuntu/+source/python3.12/tree/debian/changelog#n842
+    "MULTIARCH",
     # The versioned libpythonX.Y.so.N file. Usually?
     # It might be a static archive (.a) file instead.
     "INSTSONAME",
@@ -45,11 +53,6 @@
     # The platform-specific filename suffix for library files.
     # Includes the dot, e.g. `.so`
     "SHLIB_SUFFIX",
-    # Debian has a "multiarch" layout that has libs for different archs
-    # in slightly other locations. The MULTIARCH sysconfig varible tells
-    # which directory under `LIBDIR` these exist in, if any.
-    # See https://wiki.debian.org/Python/MultiArch
-    "MULTIARCH",
 ]
 data.update(zip(config_vars, sysconfig.get_config_vars(*config_vars)))
 print(json.dumps(data))

python/private/local_runtime_repo.bzl

@@ -136,17 +136,16 @@ def _local_runtime_repo_impl(rctx):
     for name in shared_lib_names:
         origin = rctx.path("{}/{}".format(shared_lib_dir, name))
 
+        # If the origin doesn't exist, try the multiarch location
+        if not origin.exists and multiarch:
+            origin = rctx.path("{}/{}/{}".format(shared_lib_dir, multiarch, name))
+
         # The reported names don't always exist; it depends on the particulars
         # of the runtime installation.
         if origin.exists:
             repo_utils.watch(rctx, origin)
             rctx.symlink(origin, "lib/" + name)
 
-        origin_multiarch = rctx.path("{}/{}/{}".format(shared_lib_dir, multiarch, name))
-        if origin_multiarch.exists:
-            repo_utils.watch(rctx, origin)
-            rctx.symlink(origin, "lib/{}/{}".format(multiarch, name))
-
     rctx.file("WORKSPACE", "")
     rctx.file("MODULE.bazel", "")
     rctx.file("REPO.bazel", "")