rules_python.patch

--- a/python/private/toolchain_aliases.bzl
+++ b/python/private/toolchain_aliases.bzl
@@ -43,6 +43,16 @@
             visibility = ["//visibility:private"],
         )

+    # Use a sensible default platform for unsupported target platforms (e.g., WASI).
+    # Prefer x86_64-unknown-linux-gnu as it's the most common CI/exec platform.
+    # This allows builds to proceed when Python is transitively depended on
+    # but not actually used in the target configuration.
+    default_platform = None
+    if "x86_64-unknown-linux-gnu" in platforms:
+        default_platform = "x86_64-unknown-linux-gnu"
+    elif platforms:
+        default_platform = platforms[0]
+
     prefix = name
     for name in [
         "files",
@@ -52,29 +62,39 @@
         "python_headers",
         "python_runtimes",
     ]:
+        select_dict = {
+            ":" + platform: "@{}_{}//:{}".format(prefix, platform, name)
+            for platform in platforms
+        }
+        if default_platform:
+            select_dict["//conditions:default"] = "@{}_{}//:{}".format(prefix, default_platform, name)
         native.alias(
             name = name,
-            actual = select({
-                ":" + platform: "@{}_{}//:{}".format(prefix, platform, name)
-                for platform in platforms
-            }),
+            actual = select(select_dict),
             visibility = visibility,
         )

+    python3_select_dict = {
+        ":" + platform: "@{}_{}//:{}".format(prefix, platform, "python.exe" if "windows" in platform else "bin/python3")
+        for platform in platforms
+    }
+    if default_platform:
+        python3_select_dict["//conditions:default"] = "@{}_{}//:bin/python3".format(prefix, default_platform)
     native.alias(
         name = "python3",
-        actual = select({
-            ":" + platform: "@{}_{}//:{}".format(prefix, platform, "python.exe" if "windows" in platform else "bin/python3")
-            for platform in platforms
-        }),
+        actual = select(python3_select_dict),
         visibility = visibility,
     )
+
+    pip_select_dict = {
+        ":" + platform: "@{}_{}//:python_runtimes".format(prefix, platform)
+        for platform in platforms
+        if "windows" not in platform
+    }
+    if default_platform and "windows" not in default_platform:
+        pip_select_dict["//conditions:default"] = "@{}_{}//:python_runtimes".format(prefix, default_platform)
     native.alias(
         name = "pip",
-        actual = select({
-            ":" + platform: "@{}_{}//:python_runtimes".format(prefix, platform)
-            for platform in platforms
-            if "windows" not in platform
-        }),
+        actual = select(pip_select_dict),
         visibility = visibility,
     )