1"""runpy.py - locating and running Python code using the module namespace
2
3Provides support for locating and running Python scripts using the Python
4module namespace instead of the native filesystem.
5
6This allows Python code to play nicely with non-filesystem based PEP 302
7importers when locating support scripts as well as when importing modules.
8"""
9# Written by Nick Coghlan <ncoghlan at gmail.com>
10#    to implement PEP 338 (Executing Modules as Scripts)
11
12
13import sys
14import importlib.machinery # importlib first so we can test #15386 via -m
15import importlib.util
16import types
17from pkgutil import read_code, get_importer
18
19__all__ = [
20    "run_module", "run_path",
21]
22
23class _TempModule(object):
24    """Temporarily replace a module in sys.modules with an empty namespace"""
25    def __init__(self, mod_name):
26        self.mod_name = mod_name
27        self.module = types.ModuleType(mod_name)
28        self._saved_module = []
29
30    def __enter__(self):
31        mod_name = self.mod_name
32        try:
33            self._saved_module.append(sys.modules[mod_name])
34        except KeyError:
35            pass
36        sys.modules[mod_name] = self.module
37        return self
38
39    def __exit__(self, *args):
40        if self._saved_module:
41            sys.modules[self.mod_name] = self._saved_module[0]
42        else:
43            del sys.modules[self.mod_name]
44        self._saved_module = []
45
46class _ModifiedArgv0(object):
47    def __init__(self, value):
48        self.value = value
49        self._saved_value = self._sentinel = object()
50
51    def __enter__(self):
52        if self._saved_value is not self._sentinel:
53            raise RuntimeError("Already preserving saved value")
54        self._saved_value = sys.argv[0]
55        sys.argv[0] = self.value
56
57    def __exit__(self, *args):
58        self.value = self._sentinel
59        sys.argv[0] = self._saved_value
60
61# TODO: Replace these helpers with importlib._bootstrap_external functions.
62def _run_code(code, run_globals, init_globals=None,
63              mod_name=None, mod_spec=None,
64              pkg_name=None, script_name=None):
65    """Helper to run code in nominated namespace"""
66    if init_globals is not None:
67        run_globals.update(init_globals)
68    if mod_spec is None:
69        loader = None
70        fname = script_name
71        cached = None
72    else:
73        loader = mod_spec.loader
74        fname = mod_spec.origin
75        cached = mod_spec.cached
76        if pkg_name is None:
77            pkg_name = mod_spec.parent
78    run_globals.update(__name__ = mod_name,
79                       __file__ = fname,
80                       __cached__ = cached,
81                       __doc__ = None,
82                       __loader__ = loader,
83                       __package__ = pkg_name,
84                       __spec__ = mod_spec)
85    exec(code, run_globals)
86    return run_globals
87
88def _run_module_code(code, init_globals=None,
89                    mod_name=None, mod_spec=None,
90                    pkg_name=None, script_name=None):
91    """Helper to run code in new namespace with sys modified"""
92    fname = script_name if mod_spec is None else mod_spec.origin
93    with _TempModule(mod_name) as temp_module, _ModifiedArgv0(fname):
94        mod_globals = temp_module.module.__dict__
95        _run_code(code, mod_globals, init_globals,
96                  mod_name, mod_spec, pkg_name, script_name)
97    # Copy the globals of the temporary module, as they
98    # may be cleared when the temporary module goes away
99    return mod_globals.copy()
100
101# Helper to get the full name, spec and code for a module
102def _get_module_details(mod_name, error=ImportError):
103    if mod_name.startswith("."):
104        raise error("Relative module names not supported")
105    pkg_name, _, _ = mod_name.rpartition(".")
106    if pkg_name:
107        # Try importing the parent to avoid catching initialization errors
108        try:
109            __import__(pkg_name)
110        except ImportError as e:
111            # If the parent or higher ancestor package is missing, let the
112            # error be raised by find_spec() below and then be caught. But do
113            # not allow other errors to be caught.
114            if e.name is None or (e.name != pkg_name and
115                    not pkg_name.startswith(e.name + ".")):
116                raise
117        # Warn if the module has already been imported under its normal name
118        existing = sys.modules.get(mod_name)
119        if existing is not None and not hasattr(existing, "__path__"):
120            from warnings import warn
121            msg = "{mod_name!r} found in sys.modules after import of " \
122                "package {pkg_name!r}, but prior to execution of " \
123                "{mod_name!r}; this may result in unpredictable " \
124                "behaviour".format(mod_name=mod_name, pkg_name=pkg_name)
125            warn(RuntimeWarning(msg))
126
127    try:
128        spec = importlib.util.find_spec(mod_name)
129    except (ImportError, AttributeError, TypeError, ValueError) as ex:
130        # This hack fixes an impedance mismatch between pkgutil and
131        # importlib, where the latter raises other errors for cases where
132        # pkgutil previously raised ImportError
133        msg = "Error while finding module specification for {!r} ({}: {})"
134        raise error(msg.format(mod_name, type(ex).__name__, ex)) from ex
135    if spec is None:
136        raise error("No module named %s" % mod_name)
137    if spec.submodule_search_locations is not None:
138        if mod_name == "__main__" or mod_name.endswith(".__main__"):
139            raise error("Cannot use package as __main__ module")
140        try:
141            pkg_main_name = mod_name + ".__main__"
142            return _get_module_details(pkg_main_name, error)
143        except error as e:
144            if mod_name not in sys.modules:
145                raise  # No module loaded; being a package is irrelevant
146            raise error(("%s; %r is a package and cannot " +
147                               "be directly executed") %(e, mod_name))
148    loader = spec.loader
149    if loader is None:
150        raise error("%r is a namespace package and cannot be executed"
151                                                                 % mod_name)
152    try:
153        code = loader.get_code(mod_name)
154    except ImportError as e:
155        raise error(format(e)) from e
156    if code is None:
157        raise error("No code object available for %s" % mod_name)
158    return mod_name, spec, code
159
160class _Error(Exception):
161    """Error that _run_module_as_main() should report without a traceback"""
162
163# XXX ncoghlan: Should this be documented and made public?
164# (Current thoughts: don't repeat the mistake that lead to its
165# creation when run_module() no longer met the needs of
166# mainmodule.c, but couldn't be changed because it was public)
167def _run_module_as_main(mod_name, alter_argv=True):
168    """Runs the designated module in the __main__ namespace
169
170       Note that the executed module will have full access to the
171       __main__ namespace. If this is not desirable, the run_module()
172       function should be used to run the module code in a fresh namespace.
173
174       At the very least, these variables in __main__ will be overwritten:
175           __name__
176           __file__
177           __cached__
178           __loader__
179           __package__
180    """
181    try:
182        if alter_argv or mod_name != "__main__": # i.e. -m switch
183            mod_name, mod_spec, code = _get_module_details(mod_name, _Error)
184        else:          # i.e. directory or zipfile execution
185            mod_name, mod_spec, code = _get_main_module_details(_Error)
186    except _Error as exc:
187        msg = "%s: %s" % (sys.executable, exc)
188        sys.exit(msg)
189    main_globals = sys.modules["__main__"].__dict__
190    if alter_argv:
191        sys.argv[0] = mod_spec.origin
192    return _run_code(code, main_globals, None,
193                     "__main__", mod_spec)
194
195def run_module(mod_name, init_globals=None,
196               run_name=None, alter_sys=False):
197    """Execute a module's code without importing it
198
199       Returns the resulting top level namespace dictionary
200    """
201    mod_name, mod_spec, code = _get_module_details(mod_name)
202    if run_name is None:
203        run_name = mod_name
204    if alter_sys:
205        return _run_module_code(code, init_globals, run_name, mod_spec)
206    else:
207        # Leave the sys module alone
208        return _run_code(code, {}, init_globals, run_name, mod_spec)
209
210def _get_main_module_details(error=ImportError):
211    # Helper that gives a nicer error message when attempting to
212    # execute a zipfile or directory by invoking __main__.py
213    # Also moves the standard __main__ out of the way so that the
214    # preexisting __loader__ entry doesn't cause issues
215    main_name = "__main__"
216    saved_main = sys.modules[main_name]
217    del sys.modules[main_name]
218    try:
219        return _get_module_details(main_name)
220    except ImportError as exc:
221        if main_name in str(exc):
222            raise error("can't find %r module in %r" %
223                              (main_name, sys.path[0])) from exc
224        raise
225    finally:
226        sys.modules[main_name] = saved_main
227
228
229def _get_code_from_file(run_name, fname):
230    # Check for a compiled file first
231    with open(fname, "rb") as f:
232        code = read_code(f)
233    if code is None:
234        # That didn't work, so try it as normal source code
235        with open(fname, "rb") as f:
236            code = compile(f.read(), fname, 'exec')
237    return code, fname
238
239def run_path(path_name, init_globals=None, run_name=None):
240    """Execute code located at the specified filesystem location
241
242       Returns the resulting top level namespace dictionary
243
244       The file path may refer directly to a Python script (i.e.
245       one that could be directly executed with execfile) or else
246       it may refer to a zipfile or directory containing a top
247       level __main__.py script.
248    """
249    if run_name is None:
250        run_name = "<run_path>"
251    pkg_name = run_name.rpartition(".")[0]
252    importer = get_importer(path_name)
253    # Trying to avoid importing imp so as to not consume the deprecation warning.
254    is_NullImporter = False
255    if type(importer).__module__ == 'imp':
256        if type(importer).__name__ == 'NullImporter':
257            is_NullImporter = True
258    if isinstance(importer, type(None)) or is_NullImporter:
259        # Not a valid sys.path entry, so run the code directly
260        # execfile() doesn't help as we want to allow compiled files
261        code, fname = _get_code_from_file(run_name, path_name)
262        return _run_module_code(code, init_globals, run_name,
263                                pkg_name=pkg_name, script_name=fname)
264    else:
265        # Finder is defined for path, so add it to
266        # the start of sys.path
267        sys.path.insert(0, path_name)
268        try:
269            # Here's where things are a little different from the run_module
270            # case. There, we only had to replace the module in sys while the
271            # code was running and doing so was somewhat optional. Here, we
272            # have no choice and we have to remove it even while we read the
273            # code. If we don't do this, a __loader__ attribute in the
274            # existing __main__ module may prevent location of the new module.
275            mod_name, mod_spec, code = _get_main_module_details()
276            with _TempModule(run_name) as temp_module, \
277                 _ModifiedArgv0(path_name):
278                mod_globals = temp_module.module.__dict__
279                return _run_code(code, mod_globals, init_globals,
280                                    run_name, mod_spec, pkg_name).copy()
281        finally:
282            try:
283                sys.path.remove(path_name)
284            except ValueError:
285                pass
286
287
288if __name__ == "__main__":
289    # Run the module specified as the next command line argument
290    if len(sys.argv) < 2:
291        print("No module specified for execution", file=sys.stderr)
292    else:
293        del sys.argv[0] # Make the requested module sys.argv[0]
294        _run_module_as_main(sys.argv[0])
295