backend.py

# backend.py - execute rendering, open files in viewer

import os
import re
import errno
import logging
import platform
import subprocess

from . import _compat

from . import tools

__all__ = [
    'render', 'pipe', 'version', 'view',
    'ENGINES', 'FORMATS', 'RENDERERS', 'FORMATTERS',
    'ExecutableNotFound', 'RequiredArgumentError',
]

ENGINES = {  # http://www.graphviz.org/pdf/dot.1.pdf
    'dot', 'neato', 'twopi', 'circo', 'fdp', 'sfdp', 'patchwork', 'osage',
}

FORMATS = {  # http://www.graphviz.org/doc/info/output.html
    'bmp',
    'canon', 'dot', 'gv', 'xdot', 'xdot1.2', 'xdot1.4',
    'cgimage',
    'cmap',
    'eps',
    'exr',
    'fig',
    'gd', 'gd2',
    'gif',
    'gtk',
    'ico',
    'imap', 'cmapx',
    'imap_np', 'cmapx_np',
    'ismap',
    'jp2',
    'jpg', 'jpeg', 'jpe',
    'json', 'json0', 'dot_json', 'xdot_json',  # Graphviz 2.40
    'pct', 'pict',
    'pdf',
    'pic',
    'plain', 'plain-ext',
    'png',
    'pov',
    'ps',
    'ps2',
    'psd',
    'sgi',
    'svg', 'svgz',
    'tga',
    'tif', 'tiff',
    'tk',
    'vml', 'vmlz',
    'vrml',
    'wbmp',
    'webp',
    'xlib',
    'x11',
}

RENDERERS = {  # $ dot -T:
    'cairo',
    'dot',
    'fig',
    'gd',
    'gdiplus',
    'map',
    'pic',
    'pov',
    'ps',
    'svg',
    'tk',
    'vml',
    'vrml',
    'xdot',
}

FORMATTERS = {'cairo', 'core', 'gd', 'gdiplus', 'gdwbmp', 'xlib'}

PLATFORM = platform.system().lower()


log = logging.getLogger(__name__)


class ExecutableNotFound(RuntimeError):
    """Exception raised if the Graphviz executable is not found."""

    _msg = ('failed to execute %r, '
            'make sure the Graphviz executables are on your systems\' PATH')

    def __init__(self, args):
        super(ExecutableNotFound, self).__init__(self._msg % args)


class RequiredArgumentError(Exception):
    """Exception raised if a required argument is missing."""


class CalledProcessError(_compat.CalledProcessError):

    def __str__(self):
        s = super(CalledProcessError, self).__str__()
        return '%s [stderr: %r]' % (s, self.stderr)


def command(engine, format_, filepath=None, renderer=None, formatter=None):
    """Return args list for ``subprocess.Popen`` and name of the rendered file."""
    if formatter is not None and renderer is None:
        raise RequiredArgumentError('formatter given without renderer')

    if engine not in ENGINES:
        raise ValueError('unknown engine: %r' % engine)
    if format_ not in FORMATS:
        raise ValueError('unknown format: %r' % format_)
    if renderer is not None and renderer not in RENDERERS:
        raise ValueError('unknown renderer: %r' % renderer)
    if formatter is not None and formatter not in FORMATTERS:
        raise ValueError('unknown formatter: %r' % formatter)

    output_format = [f for f in (format_, renderer, formatter) if f is not None]
    cmd = [engine, '-T%s' % ':'.join(output_format)]

    if filepath is None:
        rendered = None
    else:
        cmd.extend(['-O', filepath])
        suffix = '.'.join(reversed(output_format))
        rendered = '%s.%s' % (filepath, suffix)

    return cmd, rendered


if PLATFORM == 'windows':  # pragma: no cover
    def get_startupinfo():
        """Return subprocess.STARTUPINFO instance hiding the console window."""
        startupinfo = subprocess.STARTUPINFO()
        startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
        startupinfo.wShowWindow = subprocess.SW_HIDE
        return startupinfo
else:
    def get_startupinfo():
        """Return None for startupinfo argument of ``subprocess.Popen``."""
        return None


def run(cmd, input=None, capture_output=False, check=False, quiet=False, **kwargs):
    """Run the command described by cmd and return its (stdout, stderr) tuple."""
    log.debug('run %r', cmd)
    if input is not None:
        kwargs['stdin'] = subprocess.PIPE
    if capture_output:
        kwargs['stdout'] = kwargs['stderr'] = subprocess.PIPE

    try:
        proc = subprocess.Popen(cmd, startupinfo=get_startupinfo(), **kwargs)
    except OSError as e:
        if e.errno == errno.ENOENT:
            raise ExecutableNotFound(cmd)
        else:
            raise

    out, err = proc.communicate(input)

    if not quiet and err:
        _compat.stderr_write_bytes(err, flush=True)
    if check and proc.returncode:
        raise CalledProcessError(proc.returncode, cmd,
                                 output=out, stderr=err)

    return out, err


def render(engine, format, filepath, renderer=None, formatter=None, quiet=False):
    """Render file with Graphviz ``engine`` into ``format``,  return result filename.

    Args:
        engine: The layout commmand used for rendering (``'dot'``, ``'neato'``, ...).
        format: The output format used for rendering (``'pdf'``, ``'png'``, ...).
        filepath: Path to the DOT source file to render.
        renderer: The output renderer used for rendering (``'cairo'``, ``'gd'``, ...).
        formatter: The output formatter used for rendering (``'cairo'``, ``'gd'``, ...).
        quiet (bool): Suppress ``stderr`` output from the layout subprocess.
    Returns:
        The (possibly relative) path of the rendered file.
    Raises:
        ValueError: If ``engine``, ``format``, ``renderer``, or ``formatter`` are not known.
        graphviz.RequiredArgumentError: If ``formatter`` is given but ``renderer`` is None.
        graphviz.ExecutableNotFound: If the Graphviz executable is not found.
        subprocess.CalledProcessError: If the exit status is non-zero.

    The layout command is started from the directory of ``filepath``, so that
    references to external files (e.g. ``[image=...]``) can be given as paths
    relative to the DOT source file.
    """
    dirname, filename = os.path.split(filepath)
    cmd, rendered = command(engine, format, filename, renderer, formatter)
    if dirname:
        cwd = dirname
        rendered = os.path.join(dirname, rendered)
    else:
        cwd = None
    run(cmd, capture_output=True, cwd=cwd, check=True, quiet=quiet)
    return rendered


def pipe(engine, format, data, renderer=None, formatter=None, quiet=False):
    """Return ``data`` piped through Graphviz ``engine`` into ``format``.

    Args:
        engine: The layout commmand used for rendering (``'dot'``, ``'neato'``, ...).
        format: The output format used for rendering (``'pdf'``, ``'png'``, ...).
        data: The binary (encoded) DOT source string to render.
        renderer: The output renderer used for rendering (``'cairo'``, ``'gd'``, ...).
        formatter: The output formatter used for rendering (``'cairo'``, ``'gd'``, ...).
        quiet (bool): Suppress ``stderr`` output from the layout subprocess.
    Returns:
        Binary (encoded) stdout of the layout command.
    Raises:
        ValueError: If ``engine``, ``format``, ``renderer``, or ``formatter`` are not known.
        graphviz.RequiredArgumentError: If ``formatter`` is given but ``renderer`` is None.
        graphviz.ExecutableNotFound: If the Graphviz executable is not found.
        subprocess.CalledProcessError: If the exit status is non-zero.
    """
    cmd, _ = command(engine, format, None, renderer, formatter)
    out, _ = run(cmd, input=data, capture_output=True, check=True, quiet=quiet)
    return out


def version():
    """Return the version number tuple from the ``stderr`` output of ``dot -V``.

    Returns:
        Two, three, or four ``int`` version ``tuple``.
    Raises:
        graphviz.ExecutableNotFound: If the Graphviz executable is not found.
        subprocess.CalledProcessError: If the exit status is non-zero.
        RuntimmeError: If the output cannot be parsed into a version number.
    """
    cmd = ['dot', '-V']
    out, _ = run(cmd, check=True,
                 stdout=subprocess.PIPE,
                 stderr=subprocess.STDOUT)

    info = out.decode('ascii')
    ma = re.search(r'graphviz version (\d+\.\d+(?:\.\d+){,2}) ', info)
    if ma is None:
        raise RuntimeError('cannot parse %r output: %r' % (cmd, info))
    return tuple(int(d) for d in ma.group(1).split('.'))


def view(filepath, quiet=False):
    """Open filepath with its default viewing application (platform-specific).

    Args:
        filepath: Path to the file to open in viewer.
        quiet (bool): Suppress ``stderr`` output from the viewer process
                      (ineffective on Windows).
    Raises:
        RuntimeError: If the current platform is not supported.
    """
    try:
        view_func = getattr(view, PLATFORM)
    except AttributeError:
        raise RuntimeError('platform %r not supported' % PLATFORM)
    view_func(filepath, quiet)


@tools.attach(view, 'darwin')
def view_darwin(filepath, quiet):
    """Open filepath with its default application (mac)."""
    cmd = ['open', filepath]
    log.debug('view: %r', cmd)
    popen_func = _compat.Popen_stderr_devnull if quiet else subprocess.Popen
    popen_func(cmd)


@tools.attach(view, 'linux')
@tools.attach(view, 'freebsd')
def view_unixoid(filepath, quiet):
    """Open filepath in the user's preferred application (linux, freebsd)."""
    cmd = ['xdg-open', filepath]
    log.debug('view: %r', cmd)
    popen_func = _compat.Popen_stderr_devnull if quiet else subprocess.Popen
    popen_func(cmd)


@tools.attach(view, 'windows')
def view_windows(filepath, quiet):
    """Start filepath with its associated application (windows)."""
    # TODO: implement quiet=True
    filepath = os.path.normpath(filepath)
    log.debug('view: %r', filepath)
    os.startfile(filepath)