[CI] Speed up dependency install: dual-ABI Rust ext cache and prevalidation pruning (#33619)

scripts/ci/check_rust_ext_cache_prefix.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+"""Check that the rust-ext cache_key_prefix defaults stay in sync.
+
+The build workflow saves cache entries under its default; the download action
+restores with its own. Neither file can reference the other, and a mismatch
+makes every pool silently fall back to source builds at install time.
+"""
+
+import sys
+
+import yaml
+
+BUILD_WORKFLOW = ".github/workflows/_pr-test-rust-ext-build.yml"
+DOWNLOAD_ACTION = ".github/actions/download-rust-ext/action.yml"
+
+
+def main() -> int:
+    with open(BUILD_WORKFLOW, encoding="utf-8") as f:
+        workflow = yaml.safe_load(f)
+    with open(DOWNLOAD_ACTION, encoding="utf-8") as f:
+        action = yaml.safe_load(f)
+
+    # yaml 1.1 parses the `on:` key as boolean True
+    triggers = workflow.get("on", workflow.get(True))
+    save_prefix = triggers["workflow_call"]["inputs"]["cache_key_prefix"]["default"]
+    restore_prefix = action["inputs"]["cache_key_prefix"]["default"]
+
+    if save_prefix != restore_prefix:
+        print("ERROR: rust-ext cache_key_prefix defaults do not match.")
+        print(f"  {BUILD_WORKFLOW} saves under:    {save_prefix}")
+        print(f"  {DOWNLOAD_ACTION} restores with: {restore_prefix}")
+        print("Bump both together, or every pool falls back to source builds.")
+        return 1
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())