[BE][setup] gracefully handle envvars representing a boolean in setup.py (#156040)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/156040
Approved by: https://github.com/malfet

setup.py

@@ -221,6 +221,8 @@
 #   BUILD_PYTHON_ONLY
 #      Builds pytorch as a wheel using libtorch.so from a separate wheel
 
+from __future__ import annotations
+
 import os
 import sys
 
@@ -234,9 +236,6 @@ if sys.platform == "win32" and sys.maxsize.bit_length() == 31:
 import platform
 
 
-BUILD_LIBTORCH_WHL = os.getenv("BUILD_LIBTORCH_WHL", "0") == "1"
-BUILD_PYTHON_ONLY = os.getenv("BUILD_PYTHON_ONLY", "0") == "1"
-
 python_min_version = (3, 9, 0)
 python_min_version_str = ".".join(map(str, python_min_version))
 if sys.version_info < python_min_version:
@@ -268,6 +267,47 @@ from tools.setup_helpers.env import build_type, IS_DARWIN, IS_LINUX, IS_WINDOWS
 from tools.setup_helpers.generate_linker_script import gen_linker_script
 
 
+def str2bool(value: str | None) -> bool:
+    """Convert environment variables to boolean values."""
+    if not value:
+        return False
+    if not isinstance(value, str):
+        raise ValueError(
+            f"Expected a string value for boolean conversion, got {type(value)}"
+        )
+    value = value.strip().lower()
+    if value in (
+        "1",
+        "true",
+        "t",
+        "yes",
+        "y",
+        "on",
+        "enable",
+        "enabled",
+        "found",
+    ):
+        return True
+    if value in (
+        "0",
+        "false",
+        "f",
+        "no",
+        "n",
+        "off",
+        "disable",
+        "disabled",
+        "notfound",
+        "none",
+        "null",
+        "nil",
+        "undefined",
+        "n/a",
+    ):
+        return False
+    raise ValueError(f"Invalid string value for boolean conversion: {value}")
+
+
 def _get_package_path(package_name):
     spec = importlib.util.find_spec(package_name)
     if spec:
@@ -282,13 +322,15 @@ def _get_package_path(package_name):
     return None
 
 
+BUILD_LIBTORCH_WHL = str2bool(os.getenv("BUILD_LIBTORCH_WHL"))
+BUILD_PYTHON_ONLY = str2bool(os.getenv("BUILD_PYTHON_ONLY"))
+
 # set up appropriate env variables
 if BUILD_LIBTORCH_WHL:
     # Set up environment variables for ONLY building libtorch.so and not libtorch_python.so
     # functorch is not supported without python
     os.environ["BUILD_FUNCTORCH"] = "OFF"
 
-
 if BUILD_PYTHON_ONLY:
     os.environ["BUILD_LIBTORCHLESS"] = "ON"
     os.environ["LIBTORCH_LIB_PATH"] = f"{_get_package_path('torch')}/lib"
@@ -413,7 +455,7 @@ def check_submodules():
             os.path.isdir(folder) and len(os.listdir(folder)) == 0
         )
 
-    if bool(os.getenv("USE_SYSTEM_LIBS", False)):
+    if str2bool(os.getenv("USE_SYSTEM_LIBS")):
         return
     folders = get_submodule_folders()
     # If none of the submodule folders exists, try to initialize them
@@ -748,8 +790,7 @@ class build_ext(setuptools.command.build_ext.build_ext):
 
             # In ROCm on Windows case copy rocblas and hipblaslt files into
             # torch/lib/rocblas/library and torch/lib/hipblaslt/library
-            use_rocm = os.environ.get("USE_ROCM")
+            if str2bool(os.getenv("USE_ROCM")):
-            if use_rocm:
                 rocm_dir_path = os.environ.get("ROCM_DIR")
                 rocm_bin_path = os.path.join(rocm_dir_path, "bin")
 
@@ -1146,19 +1187,7 @@ def main():
     if BUILD_PYTHON_ONLY:
         install_requires.append(f"{LIBTORCH_PKG_NAME}=={get_torch_version()}")
 
-    use_prioritized_text = str(os.getenv("USE_PRIORITIZED_TEXT_FOR_LD", ""))
+    if str2bool(os.getenv("USE_PRIORITIZED_TEXT_FOR_LD")):
-    if (
-        use_prioritized_text == ""
-        and platform.system() == "Linux"
-        and platform.processor() == "aarch64"
-    ):
-        print_box(
-            """
-            WARNING: we strongly recommend enabling linker script optimization for ARM + CUDA.
-            To do so please export USE_PRIORITIZED_TEXT_FOR_LD=1
-            """
-        )
-    if use_prioritized_text == "1" or use_prioritized_text == "True":
         gen_linker_script(
             filein="cmake/prioritized_text.txt", fout="cmake/linker_script.ld"
         )
@@ -1170,6 +1199,13 @@ def main():
         os.environ["CXXFLAGS"] = (
             os.getenv("CXXFLAGS", "") + " -ffunction-sections -fdata-sections"
         )
+    elif platform.system() == "Linux" and platform.processor() == "aarch64":
+        print_box(
+            """
+            WARNING: we strongly recommend enabling linker script optimization for ARM + CUDA.
+            To do so please export USE_PRIORITIZED_TEXT_FOR_LD=1
+            """
+        )
 
     # Parse the command line and check the arguments before we proceed with
     # building deps and setup. We need to set values so `--help` works.