ci: Add check for mathematical constants (no macros) (acts-project#3774)

The firstly intended clang tidy check `modernize-use-std-numbers` is not suited for us:
- it doesn't flag macros like `M_PI`
- it flags values in our tables that get close to constants, which have a different basis.

benefit would have been to detect cases like `static_cast<float>(std::numbers::pi)` instead of `std::numbers::pi_v<float>` or usages of `std::sqrt(2.)` instead of `std::numbers::sqrt2`.

The updated test now checks for the classical `M_*` macros that could be accidentally used.

blocked:
- acts-project#3781

.github/workflows/checks.yml

@@ -116,6 +116,16 @@ jobs:
       - name: Check
         run: >
           CI/check_spelling
+  math_macros:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - name: Check
+        run: >
+          CI/check_math_macros.py . --exclude "thirdparty/*"
   missing_includes:
     runs-on: ubuntu-latest
     steps:

.pre-commit-config.yaml

@@ -93,3 +93,11 @@ repos:
       name: Leftover conflict markers
       language: system
       entry: git diff --staged --check
+
+  - repo: local
+    hooks:
+    - id: math_macros
+      name: math_macros
+      language: system
+      entry: CI/check_math_macros.py
+      files: \.(cpp|hpp|ipp|cu|cuh)$

CI/check_math_macros.py

@@ -0,0 +1,120 @@
+#!/usr/bin/env python3
+
+from pathlib import Path
+import os
+import argparse
+from fnmatch import fnmatch
+import re
+import sys
+
+
+math_constants = [
+    ("M_PI", "std::numbers::pi"),
+    ("M_PI_2", "std::numbers::pi / 2."),
+    ("M_PI_4", "std::numbers::pi / 4."),
+    ("M_1_PI", "std::numbers::inv_pi"),
+    ("M_2_PI", "2. * std::numbers::inv_pi"),
+    ("M_2_SQRTPI", "2. * std::numbers::inv_sqrtpi"),
+    ("M_E", "std::numbers::e"),
+    ("M_LOG2E", "std::numbers::log2e"),
+    ("M_LOG10E", "std::numbers::log10e"),
+    ("M_LN2", "std::numbers::ln2"),
+    ("M_LN10", "std::numbers::ln10"),
+    ("M_SQRT2", "std::numbers::sqrt2"),
+    ("M_SQRT1_2", "1. / std::numbers::sqrt2"),
+    ("M_SQRT3", "std::numbers::sqrt3"),
+    ("M_INV_SQRT3", "std::numbers::inv_sqrt3"),
+    ("M_EGAMMA", "std::numbers::egamma"),
+    ("M_PHI", "std::numbers::phi"),
+]
+
+
+github = "GITHUB_ACTIONS" in os.environ
+
+
+def handle_file(
+    file: Path, fix: bool, math_const: tuple[str, str]
+) -> list[tuple[int, str]]:
+    ex = re.compile(rf"(?<!\w){math_const[0]}(?!\w)")
+
+    content = file.read_text()
+    lines = content.splitlines()
+
+    changed_lines = []
+
+    for i, oline in enumerate(lines):
+        line, n_subs = ex.subn(rf"{math_const[1]}", oline)
+        lines[i] = line
+        if n_subs > 0:
+            changed_lines.append((i, oline))
+
+    if fix and len(changed_lines) > 0:
+        file.write_text("\n".join(lines) + "\n")
+
+    return changed_lines
+
+
+def main():
+    p = argparse.ArgumentParser()
+    p.add_argument("input", nargs="+")
+    p.add_argument("--fix", action="store_true", help="Attempt to fix M_* macros.")
+    p.add_argument("--exclude", "-e", action="append", default=[])
+
+    args = p.parse_args()
+
+    exit_code = 0
+
+    inputs = []
+
+    if len(args.input) == 1 and os.path.isdir(args.input[0]):
+        # walk over all files
+        for root, _, files in os.walk(args.input[0]):
+            root = Path(root)
+            for filename in files:
+                # get the full path of the file
+                filepath = root / filename
+                if filepath.suffix not in (
+                    ".hpp",
+                    ".cpp",
+                    ".ipp",
+                    ".h",
+                    ".C",
+                    ".c",
+                    ".cu",
+                    ".cuh",
+                ):
+                    continue
+
+                if any([fnmatch(str(filepath), e) for e in args.exclude]):
+                    continue
+
+                inputs.append(filepath)
+    else:
+        for file in args.input:
+            inputs.append(Path(file))
+
+    for filepath in inputs:
+        for math_const in math_constants:
+            changed_lines = handle_file(
+                file=filepath, fix=args.fix, math_const=math_const
+            )
+            if len(changed_lines) > 0:
+                exit_code = 1
+                print()
+                print(filepath)
+                for i, oline in changed_lines:
+                    print(f"{i}: {oline}")
+
+                    if github:
+                        print(
+                            f"::error file={filepath},line={i+1},title=Do not use macro {math_const[0]}::Replace {math_const[0]} with std::{math_const[1]}"
+                        )
+
+    if exit_code == 1 and github:
+        print(f"::info You will need in each flagged file #include <numbers>")
+
+    return exit_code
+
+
+if "__main__" == __name__:
+    sys.exit(main())