fix: treat ignore_root_user_error either ignored or warning

Author: mattem

CHANGELOG.md

@@ -69,6 +69,7 @@ Unreleased changes template.
 * (toolchains) Remove all but `3.8.20` versions of the Python `3.8` interpreter who has
   reached EOL. If users still need other versions of the `3.8` interpreter, please supply
   the URLs manually {bzl:ob}`python.toolchain` or {bzl:obj}`python_register_toolchains` calls.
+* (toolchains) Previously [#2636](https://github.com/bazel-contrib/rules_python/pull/2636) changed the semantics of `ignore_root_user_error` from "ignore" to "warning". This is now flipped back to ignoring the issue, and will only emit a warning when the attribute is set `False`.
 
 [20250317]: https://github.com/astral-sh/python-build-standalone/releases/tag/20250317
 

python/private/python.bzl

@@ -803,8 +803,8 @@ to spurious cache misses or build failures).
 However, if the user is running Bazel as root, this read-onlyness is not
 respected. Bazel will print a warning message when it detects that the runtime
 installation is writable despite being made read only (i.e. it's running with
-root access). If this attribute is set to `False`, Bazel will make it a hard
-error to run with root access instead.
+root access) while this attribute is set `False`, however this messaging can be ignored by setting
+this to `False`.
 """,
             mandatory = False,
         ),

python/private/python_repository.bzl

@@ -137,28 +137,30 @@ def _python_repository_impl(rctx):
             logger = logger,
         )
 
-        fail_or_warn = logger.warn if rctx.attr.ignore_root_user_error else logger.fail
-        exec_result = repo_utils.execute_unchecked(
-            rctx,
-            op = "python_repository.TestReadOnly",
-            arguments = [repo_utils.which_checked(rctx, "touch"), "lib/.test"],
-            logger = logger,
-        )
-
-        # The issue with running as root is the installation is no longer
-        # read-only, so the problems due to pyc can resurface.
-        if exec_result.return_code == 0:
-            stdout = repo_utils.execute_checked_stdout(
+        # If the user is not ignoring the warnings, then proceed to run a check,
+        # otherwise these steps can be skipped, as they both result in some warning.
+        if not rctx.attr.ignore_root_user_error:
+            exec_result = repo_utils.execute_unchecked(
                 rctx,
-                op = "python_repository.GetUserId",
-                arguments = [repo_utils.which_checked(rctx, "id"), "-u"],
+                op = "python_repository.TestReadOnly",
+                arguments = [repo_utils.which_checked(rctx, "touch"), "lib/.test"],
                 logger = logger,
             )
-            uid = int(stdout.strip())
-            if uid == 0:
-                fail_or_warn("The current user is root, which can cause spurious cache misses or build failures with the hermetic Python interpreter. See https://github.com/bazel-contrib/rules_python/pull/713.")
-            else:
-                fail_or_warn("The current user has CAP_DAC_OVERRIDE set, which can cause spurious cache misses or build failures with the hermetic Python interpreter. See https://github.com/bazel-contrib/rules_python/pull/713.")
+
+            # The issue with running as root is the installation is no longer
+            # read-only, so the problems due to pyc can resurface.
+            if exec_result.return_code == 0:
+                stdout = repo_utils.execute_checked_stdout(
+                    rctx,
+                    op = "python_repository.GetUserId",
+                    arguments = [repo_utils.which_checked(rctx, "id"), "-u"],
+                    logger = logger,
+                )
+                uid = int(stdout.strip())
+                if uid == 0:
+                    logger.warn("The current user is root, which can cause spurious cache misses or build failures with the hermetic Python interpreter. See https://github.com/bazel-contrib/rules_python/pull/713.")
+                else:
+                    logger.warn("The current user has CAP_DAC_OVERRIDE set, which can cause spurious cache misses or build failures with the hermetic Python interpreter. See https://github.com/bazel-contrib/rules_python/pull/713.")
 
     python_bin = "python.exe" if ("windows" in platform) else "bin/python3"