use vswhere.exe for python to find MSVS install if other methods fail

Author: sbSteveK

setup.py

@@ -189,6 +189,23 @@ def determine_generator_args(cmake_version=None, windows_sdk_version=None):
             elif '\\Microsoft Visual Studio 14.0' in compiler.cc:
                 vs_version = 14
                 vs_year = 2015
+            else:
+                # Fallback: use vswhere.exe when distutils can't detect the VS version
+                # (e.g. Python 3.8 distutils doesn't know about VS2026)
+                import subprocess
+                vswhere = os.path.join(
+                    os.environ.get('ProgramFiles(x86)', r'C:\Program Files (x86)'),
+                    'Microsoft Visual Studio', 'Installer', 'vswhere.exe')
+                if os.path.exists(vswhere):
+                    result = subprocess.run(
+                        [vswhere, '-latest', '-property', 'installationVersion'],
+                        capture_output=True, text=True)
+                    if result.returncode == 0 and result.stdout.strip():
+                        major = int(result.stdout.strip().split('.')[0])
+                        # VS major version -> marketing year mapping
+                        major_to_year = {14: 2015, 15: 2017, 16: 2019, 17: 2022, 18: 2026}
+                        vs_version = major
+                        vs_year = major_to_year.get(major, 2022 + (major - 17) * 3)
             assert (vs_version and vs_year)
         except Exception:
             raise RuntimeError('No supported version of MSVC compiler could be found!')