fix: validate stage0 version matches release version (#12700)

This PR fixes a CMake scoping bug that made `-DLEAN_VERSION_*` overrides
ineffective.

The version variables (`LEAN_VERSION_MAJOR`, `MINOR`, `PATCH`,
`IS_RELEASE`) were declared with plain `set()`, which creates normal
variables that shadow cache variables set by `-D` on the command line.
The fix changes them to `CACHE STRING ""` to match the existing
`LEAN_SPECIAL_VERSION_DESC` pattern.

However, `CACHE STRING ""` alone isn't sufficient because `project(LEAN
CXX C)` implicitly creates empty `LEAN_VERSION_{MAJOR,MINOR,PATCH}`
normal variables (CMake sets `<PROJECT>_VERSION_*` for the project
name). These shadow the cache values, so we `unset()` them after the
cache declarations to let `${VAR}` fall through to the cache.

Closes https://github.com/leanprover/lean4/issues/12681

🤖 Prepared with Claude Code

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.claude/CLAUDE.md

@@ -40,6 +40,10 @@ When asked to implement new features:
 - ONLY use the project's documented build command: `make -j$(nproc) -C build/release`
 - If a build is broken, ask the user before attempting any manual cleanup
 
+## stage0 Is a Copy of src
+
+**Never manually edit files under `stage0/`.** The `stage0/` directory is a snapshot of `src/` produced by `make update-stage0`. To change anything in stage0 (CMakeLists.txt, C++ source, etc.), edit the corresponding file in `src/` and let `update-stage0` propagate it.
+
 ## LSP and IDE Diagnostics
 
 After rebuilding, LSP diagnostics may be stale until the user interacts with files. Trust command-line test results over IDE diagnostics.

script/release_checklist.py

@@ -311,21 +311,22 @@ def check_cmake_version(repo_url, branch, version_major, version_minor, github_t
         print(f"  ❌ Could not retrieve {cmake_file_path} from {branch}")
         return False
 
-    expected_lines = [
-        f"set(LEAN_VERSION_MAJOR {version_major})",
-        f"set(LEAN_VERSION_MINOR {version_minor})",
-        f"set(LEAN_VERSION_PATCH 0)",
-        f"set(LEAN_VERSION_IS_RELEASE 1)"
+    expected_prefixes = [
+        f"set(LEAN_VERSION_MAJOR {version_major}",
+        f"set(LEAN_VERSION_MINOR {version_minor}",
+        f"set(LEAN_VERSION_PATCH 0",
+        f"set(LEAN_VERSION_IS_RELEASE 1"
     ]
 
-    for line in expected_lines:
-        if not any(l.strip().startswith(line) for l in content.splitlines()):
-            print(f"  ❌ Missing or incorrect line in {cmake_file_path}: {line}")
+    for prefix in expected_prefixes:
+        if not any(l.strip().startswith(prefix) for l in content.splitlines()):
+            print(f"  ❌ Missing or incorrect line in {cmake_file_path}: {prefix}...)")
             return False
 
     print(f"  ✅ CMake version settings are correct in {cmake_file_path}")
     return True
 
+
 def extract_org_repo_from_url(repo_url):
     """Extract the 'org/repo' part from a GitHub URL."""
     if repo_url.startswith("https://github.com/"):

src/CMakeLists.txt

@@ -7,11 +7,17 @@ if(NOT DEFINED STAGE)
 endif()
 include(ExternalProject)
 project(LEAN CXX C)
-set(LEAN_VERSION_MAJOR 4)
-set(LEAN_VERSION_MINOR 30)
-set(LEAN_VERSION_PATCH 0)
-set(LEAN_VERSION_IS_RELEASE 0) # This number is 1 in the release revision, and 0 otherwise.
+set(LEAN_VERSION_MAJOR 4 CACHE STRING "")
+set(LEAN_VERSION_MINOR 30 CACHE STRING "")
+set(LEAN_VERSION_PATCH 0 CACHE STRING "")
+set(LEAN_VERSION_IS_RELEASE 0 CACHE STRING "") # This number is 1 in the release revision, and 0 otherwise.
 set(LEAN_SPECIAL_VERSION_DESC "" CACHE STRING "Additional version description like 'nightly-2018-03-11'")
+# project(LEAN) above implicitly creates empty LEAN_VERSION_{MAJOR,MINOR,PATCH}
+# normal variables (CMake sets <PROJECT>_VERSION_* for the project name). These
+# shadow the cache values. Remove them so ${VAR} falls through to the cache.
+unset(LEAN_VERSION_MAJOR)
+unset(LEAN_VERSION_MINOR)
+unset(LEAN_VERSION_PATCH)
 set(LEAN_VERSION_STRING "${LEAN_VERSION_MAJOR}.${LEAN_VERSION_MINOR}.${LEAN_VERSION_PATCH}")
 if(LEAN_SPECIAL_VERSION_DESC)
   string(APPEND LEAN_VERSION_STRING "-${LEAN_SPECIAL_VERSION_DESC}")