enable windows symlinks, cleanup error handling

Author: rickeylev

.bazelrc

@@ -21,8 +21,14 @@ common --incompatible_disallow_struct_provider_syntax
 # Makes Bazel 7 act more like Bazel 8
 common --incompatible_use_plus_in_repo_names
 
-# Windows makes use of runfiles for some rules
+# Windows has enable_runfiles disabled by default, so explicitly enable it.
+# We're heavily reliant on runfile trees.
 build --enable_runfiles
+# Have Windows create symlinks instead of junctions. This requires permissions
+# to create symlinks (Developer mode, Administrator, or certain registry keys).
+# This is required because runfiles create file->file entries, but junctions
+# only work for directory->directory entries.
+startup --windows_enable_symlinks
 
 # Make Bazel 7 use bzlmod by default
 common --enable_bzlmod
@@ -45,4 +51,3 @@ build --lockfile_mode=update
 # See issue 3567. Disable implicit python zip creation.
 common --build_python_zip=false
 common --@rules_python//python/config_settings:build_python_zip=false
-startup --windows_enable_symlinks

python/private/stage2_bootstrap_template.py

@@ -70,39 +70,29 @@ def get_build_data(self):
         if is_windows():
             path = os.path.normpath(path)
         try:
-            path = os.path.dirname(__file__)
-            path = os.path.join(path, "print_build_data.build_data.txt")
-            # Use utf-8-sig to handle Windows BOM
             with open(path, 'rb') as fp:
                 data = fp.read()
+            # Use utf-8-sig to handle Windows BOM, just in case; it's easy
+            # for it to sneak in on Windows.
             return data.decode('utf-8-sig')
         except Exception as exc:
             if hasattr(exc, "add_note"):
-                exc.add_note(f"version: {sys.version}")
-                exc.add_note(f"path: {path}")
+                exc.add_note(f"python version: {sys.version}")
+                exc.add_note(f"attempted path: {path}")
                 exc.add_note(f"runfiles lookup path: {rlocation_path}")
                 exc.add_note(f"exists: {os.path.exists(path)}")
                 exc.add_note(f"lexists: {os.path.lexists(path)}")
                 exc.add_note(f"islink: {os.path.islink(path)}")
                 exc.add_note(f"isfile: {os.path.isfile(path)}")
                 if hasattr(os.path, "isjunction"):
-                    exc.add_note(f"isjunction: {os.path.isjunction(path)}")
+                    is_junction = os.path.isjunction(path)
+                else:
+                    import stat
+                    st = os.lstat(path)
+                    is_junction = bool(st.st_reparse_tag == stat.IO_REPARSE_TAG_MOUNT_POINT)
+                exc.add_note(f"isjunction: {is_junction}")
                 can_read = os.access(path, os.R_OK)
                 exc.add_note(f"readable: {can_read}")
-                try:
-                    exc.add_note(f"stat: {os.stat(path)}")
-                except Exception as e:
-                    exc.add_note(f"stat error: {e}")
-                try:
-                    exc.add_note(f"lstat: {os.lstat(path)}")
-                except Exception as e:
-                    exc.add_note(f"lstat error: {e}")
-                try:
-                    import subprocess
-                    out = subprocess.check_output(f'dir "{os.path.dirname(path)}"', shell=True)
-                    exc.add_note(f"dir: {out.decode('utf-8', 'replace')}")
-                except Exception as e:
-                    exc.add_note(f"dir error: {e}")
             raise