webbrowser.py

#! /usr/bin/env python3
"""Interfaces for launching and remotely controlling web browsers."""
# Maintained by Georg Brandl.

import os
import shlex
import shutil
import sys
import subprocess
import threading

__all__ = ["Error", "open", "open_new", "open_new_tab", "get", "register"]

class Error(Exception):
    pass

_lock = threading.RLock()
_browsers = {}                  # Dictionary of available browser controllers
_tryorder = None                # Preference order of available browsers
_os_preferred_browser = None    # The preferred browser

def register(name, klass, instance=None, *, preferred=False):
    """Register a browser connector."""
    with _lock:
        if _tryorder is None:
            register_standard_browsers()
        _browsers[name.lower()] = [klass, instance]

        # Preferred browsers go to the front of the list.
        # Need to match to the default browser returned by xdg-settings, which
        # may be of the form e.g. "firefox.desktop".
        if preferred or (_os_preferred_browser and name in _os_preferred_browser):
            _tryorder.insert(0, name)
        else:
            _tryorder.append(name)

def get(using=None):
    """Return a browser launcher instance appropriate for the environment."""
    if _tryorder is None:
        with _lock:
            if _tryorder is None:
                register_standard_browsers()
    if using is not None:
        alternatives = [using]
    else:
        alternatives = _tryorder
    for browser in alternatives:
        if '%s' in browser:
            # User gave us a command line, split it into name and args
            browser = shlex.split(browser)
            if browser[-1] == '&':
                return BackgroundBrowser(browser[:-1])
            else:
                return GenericBrowser(browser)
        else:
            # User gave us a browser name or path.
            try:
                command = _browsers[browser.lower()]
            except KeyError:
                command = _synthesize(browser)
            if command[1] is not None:
                return command[1]
            elif command[0] is not None:
                return command[0]()
    raise Error("could not locate runnable browser")

# Please note: the following definition hides a builtin function.
# It is recommended one does "import webbrowser" and uses webbrowser.open(url)
# instead of "from webbrowser import *".

def open(url, new=0, autoraise=True):
    """Display url using the default browser.

    If possible, open url in a location determined by new.
    - 0: the same browser window (the default).
    - 1: a new browser window.
    - 2: a new browser page ("tab").
    If possible, autoraise raises the window (the default) or not.
    """
    if _tryorder is None:
        with _lock:
            if _tryorder is None:
                register_standard_browsers()
    for name in _tryorder:
        browser = get(name)
        if browser.open(url, new, autoraise):
            return True
    return False

def open_new(url):
    """Open url in a new window of the default browser.

    If not possible, then open url in the only browser window.
    """
    return open(url, 1)

def open_new_tab(url):
    """Open url in a new page ("tab") of the default browser.

    If not possible, then the behavior becomes equivalent to open_new().
    """
    return open(url, 2)


def _synthesize(browser, *, preferred=False):
    """Attempt to synthesize a controller based on existing controllers.

    This is useful to create a controller when a user specifies a path to
    an entry in the BROWSER environment variable -- we can copy a general
    controller to operate using a specific installation of the desired
    browser in this way.

    If we can't create a controller in this way, or if there is no
    executable for the requested browser, return [None, None].

    """
    cmd = browser.split()[0]
    if not shutil.which(cmd):
        return [None, None]
    name = os.path.basename(cmd)
    try:
        command = _browsers[name.lower()]
    except KeyError:
        return [None, None]
    # now attempt to clone to fit the new name:
    controller = command[1]
    if controller and name.lower() == controller.basename:
        import copy
        controller = copy.copy(controller)
        controller.name = browser
        controller.basename = os.path.basename(browser)
        register(browser, None, instance=controller, preferred=preferred)
        return [None, controller]
    return [None, None]


# General parent classes

class BaseBrowser(object):
    """Parent class for all browsers. Do not use directly."""

    args = ['%s']

    def __init__(self, name=""):
        self.name = name
        self.basename = name

    def open(self, url, new=0, autoraise=True):
        raise NotImplementedError

    def open_new(self, url):
        return self.open(url, 1)

    def open_new_tab(self, url):
        return self.open(url, 2)


class GenericBrowser(BaseBrowser):
    """Class for all browsers started with a command
       and without remote functionality."""

    def __init__(self, name):
        if isinstance(name, str):
            self.name = name
            self.args = ["%s"]
        else:
            # name should be a list with arguments
            self.name = name[0]
            self.args = name[1:]
        self.basename = os.path.basename(self.name)

    def open(self, url, new=0, autoraise=True):
        sys.audit("webbrowser.open", url)
        cmdline = [self.name] + [arg.replace("%s", url)
                                 for arg in self.args]
        try:
            if sys.platform[:3] == 'win':
                p = subprocess.Popen(cmdline)
            else:
                p = subprocess.Popen(cmdline, close_fds=True)
            return not p.wait()
        except OSError:
            return False


class BackgroundBrowser(GenericBrowser):
    """Class for all browsers which are to be started in the
       background."""

    def open(self, url, new=0, autoraise=True):
        cmdline = [self.name] + [arg.replace("%s", url)
                                 for arg in self.args]
        sys.audit("webbrowser.open", url)
        try:
            if sys.platform[:3] == 'win':
                p = subprocess.Popen(cmdline)
            else:
                p = subprocess.Popen(cmdline, close_fds=True,
                                     start_new_session=True)
            return (p.poll() is None)
        except OSError:
            return False


class UnixBrowser(BaseBrowser):
    """Parent class for all Unix browsers with remote functionality."""

    raise_opts = None
    background = False
    redirect_stdout = True
    # In remote_args, %s will be replaced with the requested URL.  %action will
    # be replaced depending on the value of 'new' passed to open.
    # remote_action is used for new=0 (open).  If newwin is not None, it is
    # used for new=1 (open_new).  If newtab is not None, it is used for
    # new=3 (open_new_tab).  After both substitutions are made, any empty
    # strings in the transformed remote_args list will be removed.
    remote_args = ['%action', '%s']
    remote_action = None
    remote_action_newwin = None
    remote_action_newtab = None

    def _invoke(self, args, remote, autoraise, url=None):
        raise_opt = []
        if remote and self.raise_opts:
            # use autoraise argument only for remote invocation
            autoraise = int(autoraise)
            opt = self.raise_opts[autoraise]
            if opt: raise_opt = [opt]

        cmdline = [self.name] + raise_opt + args

        if remote or self.background:
            inout = subprocess.DEVNULL
        else:
            # for TTY browsers, we need stdin/out
            inout = None
        p = subprocess.Popen(cmdline, close_fds=True, stdin=inout,
                             stdout=(self.redirect_stdout and inout or None),
                             stderr=inout, start_new_session=True)
        if remote:
            # wait at most five seconds. If the subprocess is not finished, the
            # remote invocation has (hopefully) started a new instance.
            try:
                rc = p.wait(5)
                # if remote call failed, open() will try direct invocation
                return not rc
            except subprocess.TimeoutExpired:
                return True
        elif self.background:
            if p.poll() is None:
                return True
            else:
                return False
        else:
            return not p.wait()

    def open(self, url, new=0, autoraise=True):
        sys.audit("webbrowser.open", url)
        if new == 0:
            action = self.remote_action
        elif new == 1:
            action = self.remote_action_newwin
        elif new == 2:
            if self.remote_action_newtab is None:
                action = self.remote_action_newwin
            else:
                action = self.remote_action_newtab
        else:
            raise Error("Bad 'new' parameter to open(); " +
                        "expected 0, 1, or 2, got %s" % new)

        args = [arg.replace("%s", url).replace("%action", action)
                for arg in self.remote_args]
        args = [arg for arg in args if arg]
        success = self._invoke(args, True, autoraise, url)
        if not success:
            # remote invocation failed, try straight way
            args = [arg.replace("%s", url) for arg in self.args]
            return self._invoke(args, False, False)
        else:
            return True


class Mozilla(UnixBrowser):
    """Launcher class for Mozilla browsers."""

    remote_args = ['%action', '%s']
    remote_action = ""
    remote_action_newwin = "-new-window"
    remote_action_newtab = "-new-tab"
    background = True


class Epiphany(UnixBrowser):
    """Launcher class for Epiphany browser."""

    raise_opts = ["-noraise", ""]
    remote_args = ['%action', '%s']
    remote_action = "-n"
    remote_action_newwin = "-w"
    background = True


class Chrome(UnixBrowser):
    "Launcher class for Google Chrome browser."

    remote_args = ['%action', '%s']
    remote_action = ""
    remote_action_newwin = "--new-window"
    remote_action_newtab = ""
    background = True

Chromium = Chrome


class Opera(UnixBrowser):
    "Launcher class for Opera browser."

    remote_args = ['%action', '%s']
    remote_action = ""
    remote_action_newwin = "--new-window"
    remote_action_newtab = ""
    background = True


class Elinks(UnixBrowser):
    "Launcher class for Elinks browsers."

    remote_args = ['-remote', 'openURL(%s%action)']
    remote_action = ""
    remote_action_newwin = ",new-window"
    remote_action_newtab = ",new-tab"
    background = False

    # elinks doesn't like its stdout to be redirected -
    # it uses redirected stdout as a signal to do -dump
    redirect_stdout = False


class Konqueror(BaseBrowser):
    """Controller for the KDE File Manager (kfm, or Konqueror).

    See the output of ``kfmclient --commands``
    for more information on the Konqueror remote-control interface.
    """

    def open(self, url, new=0, autoraise=True):
        sys.audit("webbrowser.open", url)
        # XXX Currently I know no way to prevent KFM from opening a new win.
        if new == 2:
            action = "newTab"
        else:
            action = "openURL"

        devnull = subprocess.DEVNULL

        try:
            p = subprocess.Popen(["kfmclient", action, url],
                                 close_fds=True, stdin=devnull,
                                 stdout=devnull, stderr=devnull)
        except OSError:
            # fall through to next variant
            pass
        else:
            p.wait()
            # kfmclient's return code unfortunately has no meaning as it seems
            return True

        try:
            p = subprocess.Popen(["konqueror", "--silent", url],
                                 close_fds=True, stdin=devnull,
                                 stdout=devnull, stderr=devnull,
                                 start_new_session=True)
        except OSError:
            # fall through to next variant
            pass
        else:
            if p.poll() is None:
                # Should be running now.
                return True

        try:
            p = subprocess.Popen(["kfm", "-d", url],
                                 close_fds=True, stdin=devnull,
                                 stdout=devnull, stderr=devnull,
                                 start_new_session=True)
        except OSError:
            return False
        else:
            return (p.poll() is None)


class Edge(UnixBrowser):
    "Launcher class for Microsoft Edge browser."

    remote_args = ['%action', '%s']
    remote_action = ""
    remote_action_newwin = "--new-window"
    remote_action_newtab = ""
    background = True


#
# Platform support for Unix
#

# These are the right tests because all these Unix browsers require either
# a console terminal or an X display to run.

def register_X_browsers():

    # use xdg-open if around
    if shutil.which("xdg-open"):
        register("xdg-open", None, BackgroundBrowser("xdg-open"))

    # Opens an appropriate browser for the URL scheme according to
    # freedesktop.org settings (GNOME, KDE, XFCE, etc.)
    if shutil.which("gio"):
        register("gio", None, BackgroundBrowser(["gio", "open", "--", "%s"]))

    # Equivalent of gio open before 2015
    if "GNOME_DESKTOP_SESSION_ID" in os.environ and shutil.which("gvfs-open"):
        register("gvfs-open", None, BackgroundBrowser("gvfs-open"))

    # The default KDE browser
    if "KDE_FULL_SESSION" in os.environ and shutil.which("kfmclient"):
        register("kfmclient", Konqueror, Konqueror("kfmclient"))

    # Common symbolic link for the default X11 browser
    if shutil.which("x-www-browser"):
        register("x-www-browser", None, BackgroundBrowser("x-www-browser"))

    # The Mozilla browsers
    for browser in ("firefox", "iceweasel", "seamonkey", "mozilla-firefox",
                    "mozilla"):
        if shutil.which(browser):
            register(browser, None, Mozilla(browser))

    # Konqueror/kfm, the KDE browser.
    if shutil.which("kfm"):
        register("kfm", Konqueror, Konqueror("kfm"))
    elif shutil.which("konqueror"):
        register("konqueror", Konqueror, Konqueror("konqueror"))

    # Gnome's Epiphany
    if shutil.which("epiphany"):
        register("epiphany", None, Epiphany("epiphany"))

    # Google Chrome/Chromium browsers
    for browser in ("google-chrome", "chrome", "chromium", "chromium-browser"):
        if shutil.which(browser):
            register(browser, None, Chrome(browser))

    # Opera, quite popular
    if shutil.which("opera"):
        register("opera", None, Opera("opera"))


    if shutil.which("microsoft-edge"):
        register("microsoft-edge", None, Edge("microsoft-edge"))


def register_standard_browsers():
    global _tryorder
    _tryorder = []

    if sys.platform == 'darwin':
        register("MacOSX", None, MacOSXOSAScript('default'))
        register("chrome", None, MacOSXOSAScript('chrome'))
        register("firefox", None, MacOSXOSAScript('firefox'))
        register("safari", None, MacOSXOSAScript('safari'))
        # OS X can use below Unix support (but we prefer using the OS X
        # specific stuff)

    if sys.platform == "serenityos":
        # SerenityOS webbrowser, simply called "Browser".
        register("Browser", None, BackgroundBrowser("Browser"))

    if sys.platform[:3] == "win":
        # First try to use the default Windows browser
        register("windows-default", WindowsDefault)

        # Detect some common Windows browsers, fallback to Microsoft Edge
        # location in 64-bit Windows
        edge64 = os.path.join(os.environ.get("PROGRAMFILES(x86)", "C:\\Program Files (x86)"),
                              "Microsoft\\Edge\\Application\\msedge.exe")
        # location in 32-bit Windows
        edge32 = os.path.join(os.environ.get("PROGRAMFILES", "C:\\Program Files"),
                              "Microsoft\\Edge\\Application\\msedge.exe")
        for browser in ("firefox", "seamonkey", "mozilla", "chrome",
                        "opera", edge64, edge32):
            if shutil.which(browser):
                register(browser, None, BackgroundBrowser(browser))
        if shutil.which("MicrosoftEdge.exe"):
            register("microsoft-edge", None, Edge("MicrosoftEdge.exe"))
    else:
        # Prefer X browsers if present
        if os.environ.get("DISPLAY") or os.environ.get("WAYLAND_DISPLAY"):
            try:
                cmd = "xdg-settings get default-web-browser".split()
                raw_result = subprocess.check_output(cmd, stderr=subprocess.DEVNULL)
                result = raw_result.decode().strip()
            except (FileNotFoundError, subprocess.CalledProcessError, PermissionError, NotADirectoryError) :
                pass
            else:
                global _os_preferred_browser
                _os_preferred_browser = result

            register_X_browsers()

        # Also try console browsers
        if os.environ.get("TERM"):
            # Common symbolic link for the default text-based browser
            if shutil.which("www-browser"):
                register("www-browser", None, GenericBrowser("www-browser"))
            # The Links/elinks browsers <http://links.twibright.com/>
            if shutil.which("links"):
                register("links", None, GenericBrowser("links"))
            if shutil.which("elinks"):
                register("elinks", None, Elinks("elinks"))
            # The Lynx browser <https://lynx.invisible-island.net/>, <http://lynx.browser.org/>
            if shutil.which("lynx"):
                register("lynx", None, GenericBrowser("lynx"))
            # The w3m browser <http://w3m.sourceforge.net/>
            if shutil.which("w3m"):
                register("w3m", None, GenericBrowser("w3m"))

    # OK, now that we know what the default preference orders for each
    # platform are, allow user to override them with the BROWSER variable.
    if "BROWSER" in os.environ:
        userchoices = os.environ["BROWSER"].split(os.pathsep)
        userchoices.reverse()

        # Treat choices in same way as if passed into get() but do register
        # and prepend to _tryorder
        for cmdline in userchoices:
            if cmdline != '':
                cmd = _synthesize(cmdline, preferred=True)
                if cmd[1] is None:
                    register(cmdline, None, GenericBrowser(cmdline), preferred=True)

    # what to do if _tryorder is now empty?


#
# Platform support for Windows
#

if sys.platform[:3] == "win":
    class WindowsDefault(BaseBrowser):
        def open(self, url, new=0, autoraise=True):
            sys.audit("webbrowser.open", url)
            try:
                os.startfile(url)
            except OSError:
                # [Error 22] No application is associated with the specified
                # file for this operation: '<URL>'
                return False
            else:
                return True

#
# Platform support for macOS
#

if sys.platform == 'darwin':
    class MacOSXOSAScript(BaseBrowser):
        def __init__(self, name='default'):
            super().__init__(name)

        def open(self, url, new=0, autoraise=True):
            if self.name == 'default':
                script = 'open location "%s"' % url.replace('"', '%22') # opens in default browser
            else:
                script = f'''
                   tell application "%s"
                       activate
                       open location "%s"
                   end
                   '''%(self.name, url.replace('"', '%22'))

            osapipe = os.popen("osascript", "w")
            if osapipe is None:
                return False

            osapipe.write(script)
            rc = osapipe.close()
            return not rc


def main():
    import getopt
    usage = """Usage: %s [-n | -t | -h] url
    -n: open new window
    -t: open new tab
    -h, --help: show help""" % sys.argv[0]
    try:
        opts, args = getopt.getopt(sys.argv[1:], 'ntdh',['help'])
    except getopt.error as msg:
        print(msg, file=sys.stderr)
        print(usage, file=sys.stderr)
        sys.exit(1)
    new_win = 0
    for o, a in opts:
        if o == '-n': new_win = 1
        elif o == '-t': new_win = 2
        elif o == '-h' or o == '--help':
            print(usage, file=sys.stderr)
            sys.exit()
    if len(args) != 1:
        print(usage, file=sys.stderr)
        sys.exit(1)

    url = args[0]
    open(url, new_win)

    print("\a")

if __name__ == "__main__":
    main()