Tighten vendored ExternalData smoke coverage

Author: AnastaZIuk

.github/workflows/smoke.yml

@@ -61,4 +61,5 @@ jobs:
           python smoke/ci/verify_materialization.py `
             --build-dir $env:SMOKE_BUILD_DIR `
             --cache-root $env:NAM_CACHE_ROOT `
-            --expected-mode ${{ matrix.link_mode }}
+            --expected-mode ${{ matrix.link_mode }} `
+            --forbid-tree .nam/media/assets

cmake/README.md

@@ -206,6 +206,7 @@ consumer to verify:
 - Windows and Linux runners
 - explicit `symlink`, `hardlink`, and `copy` modes
 - shared cache reuse via `${{ github.workspace }}/.nam-cache`
+- absence of the legacy vendored payload staging tree under `.nam/<target>/assets`
 - post-build size and materialization statistics
 
 Typical local smoke runs are:

cmake/vendor/ExternalData-NAM.cmake

@@ -1,10 +1,5 @@
 # Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
 # file LICENSE.rst or https://cmake.org/licensing for details.
-#
-# Vendored by Nabla Asset Manifests from CMake 4.2 `ExternalData.cmake`.
-# NAM patch scope is intentionally narrow:
-# - on Windows prefer hardlinks, then symlinks, then copies when exposing
-#   objects from the content-addressed store
 
 #[=======================================================================[.rst:
 ExternalData
@@ -184,12 +179,16 @@ calling any of the functions provided by this module.
   host. The default order is ``hardlink -> symlink -> copy`` on Windows and
   ``symlink -> hardlink -> copy`` elsewhere.
 
+  When ``ExternalData_NO_SYMLINKS`` is set, the ``symlink`` mode is removed
+  from automatic selection and cannot be requested explicitly.
+
 .. variable:: ExternalData_STATE_ROOT
 
   The ``ExternalData_STATE_ROOT`` variable may be set to place module-managed
   metadata outside ``ExternalData_BINARY_ROOT``. When set, ``ExternalData``
   stores its hash records and build driver stamps under this directory while
   still materializing real data files under ``ExternalData_BINARY_ROOT``.
+  By default, these files continue to be placed next to the materialized data.
 
 .. variable:: ExternalData_OBJECT_STORES
 
@@ -576,7 +575,8 @@ function(ExternalData_add_target target)
           # Users care about the data file, so hide the hash/timestamp file.
           COMMENT "Generating ${file}"
           # Use a dedicated build stamp as the primary output so IDE
-          # generators keep an explicit build step for each materialized file.
+          # generators keep an explicit build step for each materialized file
+          # even when metadata is redirected outside the data tree.
           # List the hash record and real file as secondary outputs.
           # The files must be listed in this order so CMake can hide from the
           # make tool that a symlink target may not be newer than the input.

smoke/ci/verify_materialization.py

@@ -14,6 +14,12 @@ def parse_args() -> argparse.Namespace:
     parser.add_argument("--build-dir", required=True)
     parser.add_argument("--cache-root", required=True)
     parser.add_argument("--expected-mode", required=True, choices=("symlink", "hardlink", "copy"))
+    parser.add_argument(
+        "--forbid-tree",
+        action="append",
+        default=[],
+        help="Path relative to --build-dir that must not exist after materialization.",
+    )
     return parser.parse_args()
 
 
@@ -57,6 +63,19 @@ def main() -> int:
     if not media_root.exists():
         raise SystemExit(f"Missing materialized tree: {media_root}")
 
+    forbidden_trees: list[str] = []
+    for relative_path in args.forbid_tree:
+        forbidden_path = (build_dir / relative_path).resolve()
+        if forbidden_path.exists():
+            forbidden_trees.append(str(forbidden_path))
+
+    if forbidden_trees:
+        preview = ", ".join(forbidden_trees[:5])
+        raise SystemExit(
+            f"Expected the following paths to stay absent after materialization, "
+            f"but found {len(forbidden_trees)} present. First entries: {preview}"
+        )
+
     files = sorted(iter_files(media_root))
     if not files:
         raise SystemExit(f"No files found under {media_root}")
@@ -110,6 +129,7 @@ def main() -> int:
         "build_dir": str(build_dir),
         "cache_root": str(cache_root),
         "expected_mode": args.expected_mode,
+        "forbid_tree": args.forbid_tree,
         "file_count": len(files),
         "counts": counts,
         "logical_size_bytes": logical_size,