python module: support running the introspection script in process

If the found program happens to be sys.executable, we can do an
optimization and get the function return value instead of communicating
via subprocess + json. The results are identical either way.

mesonbuild/dependencies/python.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 from __future__ import annotations
 
-import functools, json, os, textwrap
+import functools, json, os, textwrap, sys
 from pathlib import Path
 import typing as T
 
@@ -111,21 +111,32 @@ def _check_version(self, version: str) -> bool:
     def sanity(self) -> bool:
         # Sanity check, we expect to have something that at least quacks in tune
 
-        import importlib.resources
-
-        with importlib.resources.path('mesonbuild.scripts', 'python_info.py') as f:
-            cmd = self.get_command() + [str(f)]
-            p, stdout, stderr = mesonlib.Popen_safe(cmd)
-
-        try:
-            info = json.loads(stdout)
-        except json.JSONDecodeError:
-            info = None
-            mlog.debug('Could not introspect Python (%s): exit code %d' % (str(p.args), p.returncode))
-            mlog.debug('Program stdout:\n')
-            mlog.debug(stdout)
-            mlog.debug('Program stderr:\n')
-            mlog.debug(stderr)
+        if self.path == sys.executable:
+            try:
+                from ..scripts import python_info
+                info = python_info.main()  # type: ignore[attr-defined]
+            except Exception:
+                import traceback
+                info = None
+                mlog.debug('Could not introspect internal Python')
+                mlog.debug('Error traceback:\n')
+                mlog.debug(traceback.format_exc())
+        else:
+            import importlib.resources
+            with importlib.resources.path('mesonbuild.scripts', 'python_info.py') as f:
+                cmd = self.get_command() + [os.fspath(f)]
+                print(f'running command: {cmd}')
+                print(f'running command: {mesonlib.join_args(str(s) for s in cmd)}')
+                p, stdout, stderr = mesonlib.Popen_safe(cmd)
+            try:
+                info = json.loads(stdout)
+            except json.JSONDecodeError:
+                info = None
+                mlog.debug('Could not introspect Python (%s): exit code %d' % (str(p.args), p.returncode))
+                mlog.debug('Program stdout:\n')
+                mlog.debug(stdout)
+                mlog.debug('Program stderr:\n')
+                mlog.debug(stderr)
 
         if info is not None and self._check_version(info['version']):
             self.info = T.cast('PythonIntrospectionDict', info)

mesonbuild/scripts/python_info.py

@@ -39,56 +39,58 @@ def get_distutils_paths(scheme=None, prefix=None):
 # See https://github.com/mesonbuild/meson/issues/8739.
 # XXX: We should be using sysconfig, but Debian only patches distutils.
 
-if 'deb_system' in distutils.command.install.INSTALL_SCHEMES:
-    paths = get_distutils_paths(scheme='deb_system')
-    install_paths = get_distutils_paths(scheme='deb_system', prefix='')
-else:
-    paths = sysconfig.get_paths()
-    empty_vars = {'base': '', 'platbase': '', 'installed_base': ''}
-    install_paths = sysconfig.get_paths(vars=empty_vars)
+def get_install_paths():
+    import distutils.command.install
+    if 'deb_system' in distutils.command.install.INSTALL_SCHEMES:
+        paths = get_distutils_paths(scheme='deb_system')
+        install_paths = get_distutils_paths(scheme='deb_system', prefix='')
+    else:
+        paths = sysconfig.get_paths()
+        empty_vars = {'base': '', 'platbase': '', 'installed_base': ''}
+        install_paths = sysconfig.get_paths(vars=empty_vars)
+    return paths, install_paths
 
 def links_against_libpython():
     from distutils.core import Distribution, Extension
     cmd = Distribution().get_command_obj('build_ext')
     cmd.ensure_finalized()
     return bool(cmd.get_libraries(Extension('dummy', [])))
 
-variables = sysconfig.get_config_vars()
-variables.update({'base_prefix': getattr(sys, 'base_prefix', sys.prefix)})
+def main():
+    variables = sysconfig.get_config_vars()
+    variables.update({'base_prefix': getattr(sys, 'base_prefix', sys.prefix)})
+    paths, install_paths = get_install_paths()
 
-if sys.version_info < (3, 0):
-    suffix = variables.get('SO')
-elif sys.version_info < (3, 8, 7):
-    # https://bugs.python.org/issue?@action=redirect&bpo=39825
-    from distutils.sysconfig import get_config_var
-    suffix = get_config_var('EXT_SUFFIX')
-else:
-    suffix = variables.get('EXT_SUFFIX')
+    if sys.version_info < (3, 0):
+        suffix = variables.get('SO')
+    elif sys.version_info < (3, 8, 7):
+        # https://bugs.python.org/issue?@action=redirect&bpo=39825
+        from distutils.sysconfig import get_config_var
+        suffix = get_config_var('EXT_SUFFIX')
+    else:
+        suffix = variables.get('EXT_SUFFIX')
 
-limited_api_suffix = None
-if sys.version_info >= (3, 2):
-    try:
-        from importlib.machinery import EXTENSION_SUFFIXES
-        limited_api_suffix = EXTENSION_SUFFIXES[1]
-    except Exception:
-        pass
+    limited_api_suffix = None
+    if sys.version_info >= (3, 2):
+        try:
+            from importlib.machinery import EXTENSION_SUFFIXES
+            limited_api_suffix = EXTENSION_SUFFIXES[1]
+        except Exception:
+            pass
 
-# pypy supports modules targetting the limited api but
-# does not use a special suffix to distinguish them:
-# https://doc.pypy.org/en/latest/cpython_differences.html#permitted-abi-tags-in-extensions
-if '__pypy__' in sys.builtin_module_names:
-    limited_api_suffix = suffix
+    return {
+      'variables': variables,
+      'paths': paths,
+      'sysconfig_paths': sysconfig.get_paths(),
+      'install_paths': install_paths,
+      'version': sysconfig.get_python_version(),
+      'platform': sysconfig.get_platform(),
+      'is_pypy': '__pypy__' in sys.builtin_module_names,
+      'is_venv': sys.prefix != variables['base_prefix'],
+      'link_libpython': links_against_libpython(),
+      'suffix': suffix,
+      'limited_api_suffix': limited_api_suffix,
+    }
 
-print(json.dumps({
-  'variables': variables,
-  'paths': paths,
-  'sysconfig_paths': sysconfig.get_paths(),
-  'install_paths': install_paths,
-  'version': sysconfig.get_python_version(),
-  'platform': sysconfig.get_platform(),
-  'is_pypy': '__pypy__' in sys.builtin_module_names,
-  'is_venv': sys.prefix != variables['base_prefix'],
-  'link_libpython': links_against_libpython(),
-  'suffix': suffix,
-  'limited_api_suffix': limited_api_suffix,
-}))
+if __name__ == '__main__':
+    print(json.dumps(main()))