utils.py

"""Notebook related utilities"""
# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.
import asyncio
import errno
import importlib.util
import inspect
import os
import socket
import sys
from contextlib import contextmanager
from urllib.parse import urljoin  # noqa: F401
from urllib.parse import SplitResult, quote, unquote, urlparse, urlsplit, urlunsplit
from urllib.request import pathname2url  # noqa: F401

from _frozen_importlib_external import _NamespacePath
from packaging.version import Version
from tornado.httpclient import AsyncHTTPClient, HTTPClient, HTTPRequest
from tornado.netutil import Resolver


def url_path_join(*pieces):
    """Join components of url into a relative url

    Use to prevent double slash when joining subpath. This will leave the
    initial and final / in place
    """
    initial = pieces[0].startswith("/")
    final = pieces[-1].endswith("/")
    stripped = [s.strip("/") for s in pieces]
    result = "/".join(s for s in stripped if s)
    if initial:
        result = "/" + result
    if final:
        result = result + "/"
    if result == "//":
        result = "/"
    return result


def url_is_absolute(url):
    """Determine whether a given URL is absolute"""
    return urlparse(url).path.startswith("/")


def path2url(path):
    """Convert a local file path to a URL"""
    pieces = [quote(p) for p in path.split(os.sep)]
    # preserve trailing /
    if pieces[-1] == "":
        pieces[-1] = "/"
    url = url_path_join(*pieces)
    return url


def url2path(url):
    """Convert a URL to a local file path"""
    pieces = [unquote(p) for p in url.split("/")]
    path = os.path.join(*pieces)
    return path


def url_escape(path):
    """Escape special characters in a URL path

    Turns '/foo bar/' into '/foo%20bar/'
    """
    parts = path.split("/")
    return "/".join([quote(p) for p in parts])


def url_unescape(path):
    """Unescape special characters in a URL path

    Turns '/foo%20bar/' into '/foo bar/'
    """
    return "/".join([unquote(p) for p in path.split("/")])


def samefile_simple(path, other_path):
    """
    Fill in for os.path.samefile when it is unavailable (Windows+py2).

    Do a case-insensitive string comparison in this case
    plus comparing the full stat result (including times)
    because Windows + py2 doesn't support the stat fields
    needed for identifying if it's the same file (st_ino, st_dev).

    Only to be used if os.path.samefile is not available.

    Parameters
    ----------
    path : String representing a path to a file
    other_path : String representing a path to another file

    Returns
    -------
    same:   Boolean that is True if both path and other path are the same
    """
    path_stat = os.stat(path)
    other_path_stat = os.stat(other_path)
    return path.lower() == other_path.lower() and path_stat == other_path_stat


def to_os_path(path, root=""):
    """Convert an API path to a filesystem path

    If given, root will be prepended to the path.
    root must be a filesystem path already.
    """
    parts = path.strip("/").split("/")
    parts = [p for p in parts if p != ""]  # remove duplicate splits
    path = os.path.join(root, *parts)
    return os.path.normpath(path)


def to_api_path(os_path, root=""):
    """Convert a filesystem path to an API path

    If given, root will be removed from the path.
    root must be a filesystem path already.
    """
    if os_path.startswith(root):
        os_path = os_path[len(root) :]
    parts = os_path.strip(os.path.sep).split(os.path.sep)
    parts = [p for p in parts if p != ""]  # remove duplicate splits
    path = "/".join(parts)
    return path


def check_version(v, check):
    """check version string v >= check

    If dev/prerelease tags result in TypeError for string-number comparison,
    it is assumed that the dependency is satisfied.
    Users on dev branches are responsible for keeping their own packages up to date.
    """
    try:
        return Version(v) >= Version(check)
    except TypeError:
        return True


# Copy of IPython.utils.process.check_pid:


def _check_pid_win32(pid):
    import ctypes

    # OpenProcess returns 0 if no such process (of ours) exists
    # positive int otherwise
    return bool(ctypes.windll.kernel32.OpenProcess(1, 0, pid))  # type:ignore[attr-defined]


def _check_pid_posix(pid):
    """Copy of IPython.utils.process.check_pid"""
    try:
        os.kill(pid, 0)
    except OSError as err:
        if err.errno == errno.ESRCH:
            return False
        elif err.errno == errno.EPERM:
            # Don't have permission to signal the process - probably means it exists
            return True
        raise
    else:
        return True


if sys.platform == "win32":
    check_pid = _check_pid_win32
else:
    check_pid = _check_pid_posix


async def ensure_async(obj):
    """Convert a non-awaitable object to a coroutine if needed,
    and await it if it was not already awaited.
    """
    if inspect.isawaitable(obj):
        try:
            result = await obj
        except RuntimeError as e:
            if str(e) == "cannot reuse already awaited coroutine":
                # obj is already the coroutine's result
                return obj
            raise
        return result
    # obj doesn't need to be awaited
    return obj


def run_sync(maybe_async):
    """If async, runs maybe_async and blocks until it has executed,
    possibly creating an event loop.
    If not async, just returns maybe_async as it is the result of something
    that has already executed.

    Parameters
    ----------
    maybe_async : async or non-async object
        The object to be executed, if it is async.

    Returns
    -------
    result
        Whatever the async object returns, or the object itself.
    """
    if not inspect.isawaitable(maybe_async):
        # that was not something async, just return it
        return maybe_async
    # it is async, we need to run it in an event loop

    def wrapped():
        create_new_event_loop = False
        try:
            loop = asyncio.get_event_loop()
        except RuntimeError:
            create_new_event_loop = True
        else:
            if loop.is_closed():
                create_new_event_loop = True
        if create_new_event_loop:
            loop = asyncio.new_event_loop()
            asyncio.set_event_loop(loop)
        try:
            result = loop.run_until_complete(maybe_async)
        except RuntimeError as e:
            if str(e) == "This event loop is already running":
                # just return a Future, hoping that it will be awaited
                result = asyncio.ensure_future(maybe_async)
            else:
                raise e
        return result

    return wrapped()


async def run_sync_in_loop(maybe_async):
    """Runs a function synchronously whether it is an async function or not.

    If async, runs maybe_async and blocks until it has executed.

    If not async, just returns maybe_async as it is the result of something
    that has already executed.

    Parameters
    ----------
    maybe_async : async or non-async object
        The object to be executed, if it is async.

    Returns
    -------
    result
        Whatever the async object returns, or the object itself.
    """
    if not inspect.isawaitable(maybe_async):
        return maybe_async
    return await maybe_async


def urlencode_unix_socket_path(socket_path):
    """Encodes a UNIX socket path string from a socket path for the `http+unix` URI form."""
    return socket_path.replace("/", "%2F")


def urldecode_unix_socket_path(socket_path):
    """Decodes a UNIX sock path string from an encoded sock path for the `http+unix` URI form."""
    return socket_path.replace("%2F", "/")


def urlencode_unix_socket(socket_path):
    """Encodes a UNIX socket URL from a socket path for the `http+unix` URI form."""
    return "http+unix://%s" % urlencode_unix_socket_path(socket_path)


def unix_socket_in_use(socket_path):
    """Checks whether a UNIX socket path on disk is in use by attempting to connect to it."""
    if not os.path.exists(socket_path):
        return False

    try:
        sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
        sock.connect(socket_path)
    except OSError:
        return False
    else:
        return True
    finally:
        sock.close()


@contextmanager
def _request_for_tornado_client(urlstring, method="GET", body=None, headers=None):
    """A utility that provides a context that handles
    HTTP, HTTPS, and HTTP+UNIX request.
    Creates a tornado HTTPRequest object with a URL
    that tornado's HTTPClients can accept.
    If the request is made to a unix socket, temporarily
    configure the AsyncHTTPClient to resolve the URL
    and connect to the proper socket.
    """
    parts = urlsplit(urlstring)
    if parts.scheme in ["http", "https"]:
        pass
    elif parts.scheme == "http+unix":
        # If unix socket, mimic HTTP.
        parts = SplitResult(
            scheme="http",
            netloc=parts.netloc,
            path=parts.path,
            query=parts.query,
            fragment=parts.fragment,
        )

        class UnixSocketResolver(Resolver):
            """A resolver that routes HTTP requests to unix sockets
            in tornado HTTP clients.
            Due to constraints in Tornados' API, the scheme of the
            must be `http` (not `http+unix`). Applications should replace
            the scheme in URLS before making a request to the HTTP client.
            """

            def initialize(self, resolver):
                self.resolver = resolver

            def close(self):
                self.resolver.close()

            async def resolve(self, host, port, *args, **kwargs):
                return [(socket.AF_UNIX, urldecode_unix_socket_path(host))]

        resolver = UnixSocketResolver(resolver=Resolver())
        AsyncHTTPClient.configure(None, resolver=resolver)
    else:
        raise Exception("Unknown URL scheme.")

    # Yield the request for the given client.
    url = urlunsplit(parts)
    request = HTTPRequest(url, method=method, body=body, headers=headers, validate_cert=False)
    yield request


def fetch(urlstring, method="GET", body=None, headers=None):
    """
    Send a HTTP, HTTPS, or HTTP+UNIX request
    to a Tornado Web Server. Returns a tornado HTTPResponse.
    """
    with _request_for_tornado_client(
        urlstring, method=method, body=body, headers=headers
    ) as request:
        response = HTTPClient(AsyncHTTPClient).fetch(request)
    return response


async def async_fetch(urlstring, method="GET", body=None, headers=None, io_loop=None):
    """
    Send an asynchronous HTTP, HTTPS, or HTTP+UNIX request
    to a Tornado Web Server. Returns a tornado HTTPResponse.
    """
    with _request_for_tornado_client(
        urlstring, method=method, body=body, headers=headers
    ) as request:
        response = await AsyncHTTPClient(io_loop).fetch(request)
    return response


def is_namespace_package(namespace):
    """Is the provided namespace a Python Namespace Package (PEP420).

    https://www.python.org/dev/peps/pep-0420/#specification

    Returns `None` if module is not importable.

    """
    # NOTE: using submodule_search_locations because the loader can be None
    try:
        spec = importlib.util.find_spec(namespace)
    except ValueError:  # spec is not set - see https://docs.python.org/3/library/importlib.html#importlib.util.find_spec
        return None

    if not spec:
        # e.g. module not installed
        return None
    return isinstance(spec.submodule_search_locations, _NamespacePath)


def filefind(filename, path_dirs=None):
    """Find a file by looking through a sequence of paths.
    This iterates through a sequence of paths looking for a file and returns
    the full, absolute path of the first occurence of the file.  If no set of
    path dirs is given, the filename is tested as is, after running through
    :func:`expandvars` and :func:`expanduser`.  Thus a simple call::
        filefind('myfile.txt')
    will find the file in the current working dir, but::
        filefind('~/myfile.txt')
    Will find the file in the users home directory.  This function does not
    automatically try any paths, such as the cwd or the user's home directory.
    Parameters
    ----------
    filename : str
        The filename to look for.
    path_dirs : str, None or sequence of str
        The sequence of paths to look for the file in.  If None, the filename
        need to be absolute or be in the cwd.  If a string, the string is
        put into a sequence and the searched.  If a sequence, walk through
        each element and join with ``filename``, calling :func:`expandvars`
        and :func:`expanduser` before testing for existence.
    Returns
    -------
    Raises :exc:`IOError` or returns absolute path to file.
    """

    # If paths are quoted, abspath gets confused, strip them...
    filename = filename.strip('"').strip("'")
    # If the input is an absolute path, just check it exists
    if os.path.isabs(filename) and os.path.isfile(filename):
        return filename

    if path_dirs is None:
        path_dirs = ("",)
    elif isinstance(path_dirs, str):
        path_dirs = (path_dirs,)

    for path in path_dirs:
        if path == ".":
            path = os.getcwd()
        testname = expand_path(os.path.join(path, filename))
        if os.path.isfile(testname):
            return os.path.abspath(testname)

    raise OSError(f"File {filename!r} does not exist in any of the search paths: {path_dirs!r}")


def expand_path(s):
    """Expand $VARS and ~names in a string, like a shell
    :Examples:
       In [2]: os.environ['FOO']='test'
       In [3]: expand_path('variable FOO is $FOO')
       Out[3]: 'variable FOO is test'
    """
    # This is a pretty subtle hack. When expand user is given a UNC path
    # on Windows (\\server\share$\%username%), os.path.expandvars, removes
    # the $ to get (\\server\share\%username%). I think it considered $
    # alone an empty var. But, we need the $ to remains there (it indicates
    # a hidden share).
    if os.name == "nt":
        s = s.replace("$\\", "IPYTHON_TEMP")
    s = os.path.expandvars(os.path.expanduser(s))
    if os.name == "nt":
        s = s.replace("IPYTHON_TEMP", "$\\")
    return s


def import_item(name):
    """Import and return ``bar`` given the string ``foo.bar``.
    Calling ``bar = import_item("foo.bar")`` is the functional equivalent of
    executing the code ``from foo import bar``.
    Parameters
    ----------
    name : string
      The fully qualified name of the module/package being imported.
    Returns
    -------
    mod : module object
       The module that was imported.
    """

    parts = name.rsplit(".", 1)
    if len(parts) == 2:
        # called with 'foo.bar....'
        package, obj = parts
        module = __import__(package, fromlist=[obj])
        try:
            pak = getattr(module, obj)
        except AttributeError:
            raise ImportError("No module named %s" % obj)
        return pak
    else:
        # called with un-dotted string
        return __import__(parts[0])