tools: Add lint for CONSTEXPR (#94089)

Adds a lint for CONSTEXPR to have us prefer to use macros for cuda files to support VS2017 compilations on windows internally (Meta)

Follow up to https://github.com/pytorch/pytorch/pull/94091

Signed-off-by: Eli Uriegas <eliuriegas@meta.com>

Pull Request resolved: https://github.com/pytorch/pytorch/pull/94089
Approved by: https://github.com/malfet

.lintrunner.toml

@@ -345,6 +345,17 @@ command = [
 ]
 is_formatter = true
 
+[[linter]]
+code = 'CONSTEXPR'
+include_patterns=['aten/src/ATen/native/cuda/*.cu']
+command = [
+    'python3',
+    'tools/linter/adapters/constexpr_linter.py',
+    '--',
+    '@{{PATHSFILE}}',
+]
+is_formatter = true
+
 [[linter]]
 code = 'SPACES'
 include_patterns = ['**']

tools/linter/adapters/constexpr_linter.py

@@ -0,0 +1,94 @@
+"""
+CONSTEXPR: Ensures users don't use vanilla constexpr since it causes issues
+"""
+
+import argparse
+import json
+import logging
+import sys
+
+from enum import Enum
+from typing import NamedTuple, Optional
+
+CONSTEXPR = "constexpr char"
+CONSTEXPR_MACRO = "CONSTEXPR_EXCEPT_WIN_CUDA char"
+
+LINTER_CODE = "CONSTEXPR"
+
+
+class LintSeverity(str, Enum):
+    ERROR = "error"
+
+
+class LintMessage(NamedTuple):
+    path: Optional[str]
+    line: Optional[int]
+    char: Optional[int]
+    code: str
+    severity: LintSeverity
+    name: str
+    original: Optional[str]
+    replacement: Optional[str]
+    description: Optional[str]
+
+
+def check_file(filename: str) -> Optional[LintMessage]:
+    logging.debug("Checking file %s", filename)
+
+    with open(filename, "r") as f:
+        lines = f.readlines()
+
+    for idx, line in enumerate(lines):
+        if CONSTEXPR in line:
+            original = "".join(lines)
+            replacement = original.replace(CONSTEXPR, CONSTEXPR_MACRO)
+            logging.debug(f"replacement: {replacement}")
+            return LintMessage(
+                path=filename,
+                line=idx,
+                char=None,
+                code=LINTER_CODE,
+                severity=LintSeverity.ERROR,
+                name="Vanilla constexpr used, prefer macros",
+                original=original,
+                replacement=replacement,
+                description="Vanilla constexpr used, prefer macros run `lintrunner --take CONSTEXPR -a` to apply changes.",
+            )
+    return None
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(
+        description="CONSTEXPR linter",
+        fromfile_prefix_chars="@",
+    )
+    parser.add_argument(
+        "--verbose",
+        action="store_true",
+    )
+    parser.add_argument(
+        "filenames",
+        nargs="+",
+        help="paths to lint",
+    )
+
+    args = parser.parse_args()
+
+    logging.basicConfig(
+        format="<%(threadName)s:%(levelname)s> %(message)s",
+        level=logging.NOTSET
+        if args.verbose
+        else logging.DEBUG
+        if len(args.filenames) < 1000
+        else logging.INFO,
+        stream=sys.stderr,
+    )
+
+    lint_messages = []
+    for filename in args.filenames:
+        lint_message = check_file(filename)
+        if lint_message is not None:
+            lint_messages.append(lint_message)
+
+    for lint_message in lint_messages:
+        print(json.dumps(lint_message._asdict()), flush=True)