cola/core.py

   1 """This module provides core functions for handling unicode and UNIX quirks
   2
   3 The @interruptable functions retry when system calls are interrupted,
   4 e.g. when python raises an IOError or OSError with errno == EINTR.
   5
   6 """
   7 from __future__ import division, absolute_import, unicode_literals
   8 import functools
   9 import itertools
  10 import mimetypes
  11 import os
  12 import platform
  13 import subprocess
  14 import sys
  15
  16 from .decorators import interruptable
  17 from .compat import ustr
  18 from .compat import PY2
  19 from .compat import PY3
  20 from .compat import WIN32
  21
  22 # /usr/include/stdlib.h
  23 # #define EXIT_SUCCESS    0   /* Successful exit status.  */
  24 # #define EXIT_FAILURE    1   /* Failing exit status.  */
  25 EXIT_SUCCESS = 0
  26 EXIT_FAILURE = 1
  27
  28 # /usr/include/sysexits.h
  29 # #define EX_USAGE        64  /* command line usage error */
  30 # #define EX_NOINPUT      66  /* cannot open input */
  31 # #define EX_UNAVAILABLE  69  /* service unavailable */
  32 EXIT_USAGE = 64
  33 EXIT_NOINPUT = 66
  34 EXIT_UNAVAILABLE = 69
  35
  36 # Default encoding
  37 ENCODING = 'utf-8'
  38
  39 # Some files are not in UTF-8; some other aren't in any codification.
  40 # Remember that GIT doesn't care about encodings (saves binary data)
  41 _encoding_tests = [
  42     ENCODING,
  43     'iso-8859-15',
  44     'windows1252',
  45     'ascii',
  46     # <-- add encodings here
  47 ]
  48
  49
  50 class UStr(ustr):
  51     """Unicode string wrapper that remembers its encoding
  52
  53     UStr wraps unicode strings to provide the `encoding` attribute.
  54     UStr is used when decoding strings of an unknown encoding.
  55     In order to generate patches that contain the original byte sequences,
  56     we must preserve the original encoding when calling decode()
  57     so that it can later be used when reconstructing the original
  58     byte sequences.
  59
  60     """
  61
  62     def __new__(cls, string, encoding):
  63
  64         if isinstance(string, UStr):
  65             if encoding != string.encoding:
  66                 raise ValueError(
  67                     'Encoding conflict: %s vs. %s' % (string.encoding, encoding)
  68                 )
  69             string = ustr(string)
  70
  71         obj = ustr.__new__(cls, string)
  72         obj.encoding = encoding
  73         return obj
  74
  75
  76 def decode_maybe(value, encoding, errors='strict'):
  77     """Decode a value when the "decode" method exists"""
  78     if hasattr(value, 'decode'):
  79         result = value.decode(encoding, errors=errors)
  80     else:
  81         result = value
  82     return result
  83
  84
  85 def decode(value, encoding=None, errors='strict'):
  86     """decode(encoded_string) returns an unencoded unicode string"""
  87     if value is None:
  88         result = None
  89     elif isinstance(value, ustr):
  90         result = UStr(value, ENCODING)
  91     elif encoding == 'bytes':
  92         result = value
  93     else:
  94         result = None
  95         if encoding is None:
  96             encoding_tests = _encoding_tests
  97         else:
  98             encoding_tests = itertools.chain([encoding], _encoding_tests)
  99
 100         for enc in encoding_tests:
 101             try:
 102                 decoded = value.decode(enc, errors)
 103                 result = UStr(decoded, enc)
 104                 break
 105             except ValueError:
 106                 pass
 107
 108         if result is None:
 109             decoded = value.decode(ENCODING, errors='ignore')
 110             result = UStr(decoded, ENCODING)
 111
 112     return result
 113
 114
 115 def encode(string, encoding=None):
 116     """encode(unencoded_string) returns a string encoded in utf-8"""
 117     if not isinstance(string, ustr):
 118         return string
 119     return string.encode(encoding or ENCODING, 'replace')
 120
 121
 122 def mkpath(path, encoding=None):
 123     # The Windows API requires unicode strings regardless of python version
 124     if WIN32:
 125         return decode(path, encoding=encoding)
 126     # UNIX prefers bytes
 127     return encode(path, encoding=encoding)
 128
 129
 130 def list2cmdline(cmd):
 131     return subprocess.list2cmdline([decode(c) for c in cmd])
 132
 133
 134 def read(filename, size=-1, encoding=None, errors='strict'):
 135     """Read filename and return contents"""
 136     with xopen(filename, 'rb') as fh:
 137         return xread(fh, size=size, encoding=encoding, errors=errors)
 138
 139
 140 def write(path, contents, encoding=None):
 141     """Writes a unicode string to a file"""
 142     with xopen(path, 'wb') as fh:
 143         return xwrite(fh, contents, encoding=encoding)
 144
 145
 146 @interruptable
 147 def xread(fh, size=-1, encoding=None, errors='strict'):
 148     """Read from a filehandle and retry when interrupted"""
 149     return decode(fh.read(size), encoding=encoding, errors=errors)
 150
 151
 152 @interruptable
 153 def xwrite(fh, content, encoding=None):
 154     """Write to a filehandle and retry when interrupted"""
 155     return fh.write(encode(content, encoding=encoding))
 156
 157
 158 @interruptable
 159 def wait(proc):
 160     """Wait on a subprocess and retry when interrupted"""
 161     return proc.wait()
 162
 163
 164 @interruptable
 165 def readline(fh, encoding=None):
 166     return decode(fh.readline(), encoding=encoding)
 167
 168
 169 @interruptable
 170 def start_command(
 171     cmd,
 172     cwd=None,
 173     add_env=None,
 174     universal_newlines=False,
 175     stdin=subprocess.PIPE,
 176     stdout=subprocess.PIPE,
 177     no_win32_startupinfo=False,
 178     stderr=subprocess.PIPE,
 179     **extra
 180 ):
 181     """Start the given command, and return a subprocess object.
 182
 183     This provides a simpler interface to the subprocess module.
 184
 185     """
 186     env = extra.pop('env', None)
 187     if add_env is not None:
 188         env = os.environ.copy()
 189         env.update(add_env)
 190
 191     # Python3 on windows always goes through list2cmdline() internally inside
 192     # of subprocess.py so we must provide unicode strings here otherwise
 193     # Python3 breaks when bytes are provided.
 194     #
 195     # Additionally, the preferred usage on Python3 is to pass unicode
 196     # strings to subprocess.  Python will automatically encode into the
 197     # default encoding (utf-8) when it gets unicode strings.
 198     shell = extra.get('shell', False)
 199     cmd = prep_for_subprocess(cmd, shell=shell)
 200
 201     if WIN32 and cwd == getcwd():
 202         # Windows cannot deal with passing a cwd that contains unicode
 203         # but we luckily can pass None when the supplied cwd is the same
 204         # as our current directory and get the same effect.
 205         # Not doing this causes unicode encoding errors when launching
 206         # the subprocess.
 207         cwd = None
 208
 209     if PY2 and cwd:
 210         cwd = encode(cwd)
 211
 212     if WIN32:
 213         # If git-cola is invoked on Windows using "start pythonw git-cola",
 214         # a console window will briefly flash on the screen each time
 215         # git-cola invokes git, which is very annoying.  The code below
 216         # prevents this by ensuring that any window will be hidden.
 217         startupinfo = subprocess.STARTUPINFO()
 218         startupinfo.dwFlags = subprocess.STARTF_USESHOWWINDOW
 219         startupinfo.wShowWindow = subprocess.SW_HIDE
 220         extra['startupinfo'] = startupinfo
 221
 222         if WIN32 and not no_win32_startupinfo:
 223             CREATE_NO_WINDOW = 0x08000000
 224             extra['creationflags'] = CREATE_NO_WINDOW
 225
 226     # Use line buffering when in text/universal_newlines mode,
 227     # otherwise use the system default buffer size.
 228     bufsize = 1 if universal_newlines else -1
 229     return subprocess.Popen(
 230         cmd,
 231         bufsize=bufsize,
 232         stdin=stdin,
 233         stdout=stdout,
 234         stderr=stderr,
 235         cwd=cwd,
 236         env=env,
 237         universal_newlines=universal_newlines,
 238         **extra
 239     )
 240
 241
 242 def prep_for_subprocess(cmd, shell=False):
 243     """Decode on Python3, encode on Python2"""
 244     # See the comment in start_command()
 245     if shell:
 246         if PY3:
 247             cmd = decode(cmd)
 248         else:
 249             cmd = encode(cmd)
 250     else:
 251         if PY3:
 252             cmd = [decode(c) for c in cmd]
 253         else:
 254             cmd = [encode(c) for c in cmd]
 255     return cmd
 256
 257
 258 @interruptable
 259 def communicate(proc):
 260     return proc.communicate()
 261
 262
 263 def run_command(cmd, *args, **kwargs):
 264     """Run the given command to completion, and return its results.
 265
 266     This provides a simpler interface to the subprocess module.
 267     The results are formatted as a 3-tuple: (exit_code, output, errors)
 268     The other arguments are passed on to start_command().
 269
 270     """
 271     encoding = kwargs.pop('encoding', None)
 272     process = start_command(cmd, *args, **kwargs)
 273     (output, errors) = communicate(process)
 274     output = decode(output, encoding=encoding)
 275     errors = decode(errors, encoding=encoding)
 276     exit_code = process.returncode
 277     return (exit_code, output or UStr('', ENCODING), errors or UStr('', ENCODING))
 278
 279
 280 @interruptable
 281 def _fork_posix(args, cwd=None, shell=False):
 282     """Launch a process in the background."""
 283     encoded_args = [encode(arg) for arg in args]
 284     return subprocess.Popen(encoded_args, cwd=cwd, shell=shell).pid
 285
 286
 287 def _fork_win32(args, cwd=None, shell=False):
 288     """Launch a background process using crazy win32 voodoo."""
 289     # This is probably wrong, but it works.  Windows.. wow.
 290     if args[0] == 'git-dag':
 291         # win32 can't exec python scripts
 292         args = [sys.executable] + args
 293
 294     if not shell:
 295         args[0] = _win32_find_exe(args[0])
 296
 297     if PY3:
 298         # see comment in start_command()
 299         argv = [decode(arg) for arg in args]
 300     else:
 301         argv = [encode(arg) for arg in args]
 302
 303     DETACHED_PROCESS = 0x00000008  # Amazing!
 304     return subprocess.Popen(
 305         argv, cwd=cwd, creationflags=DETACHED_PROCESS, shell=shell
 306     ).pid
 307
 308
 309 def _win32_find_exe(exe):
 310     """Find the actual file for a Windows executable.
 311
 312     This function goes through the same process that the Windows shell uses to
 313     locate an executable, taking into account the PATH and PATHEXT environment
 314     variables.  This allows us to avoid passing shell=True to subprocess.Popen.
 315
 316     For reference, see:
 317     http://technet.microsoft.com/en-us/library/cc723564.aspx#XSLTsection127121120120
 318
 319     """
 320     # try the argument itself
 321     candidates = [exe]
 322     # if argument does not have an extension, also try it with each of the
 323     # extensions specified in PATHEXT
 324     if '.' not in exe:
 325         extensions = getenv('PATHEXT', '').split(os.pathsep)
 326         candidates.extend([(exe + ext) for ext in extensions if ext.startswith('.')])
 327     # search the current directory first
 328     for candidate in candidates:
 329         if exists(candidate):
 330             return candidate
 331     # if the argument does not include a path separator, search each of the
 332     # directories on the PATH
 333     if not os.path.dirname(exe):
 334         for path in getenv('PATH').split(os.pathsep):
 335             if path:
 336                 for candidate in candidates:
 337                     full_path = os.path.join(path, candidate)
 338                     if exists(full_path):
 339                         return full_path
 340     # not found, punt and return the argument unchanged
 341     return exe
 342
 343
 344 # Portability wrappers
 345 if sys.platform == 'win32' or sys.platform == 'cygwin':
 346     fork = _fork_win32
 347 else:
 348     fork = _fork_posix
 349
 350
 351 def _decorator_noop(x):
 352     return x
 353
 354
 355 def wrap(action, fn, decorator=None):
 356     """Wrap arguments with `action`, optionally decorate the result"""
 357     if decorator is None:
 358         decorator = _decorator_noop
 359
 360     @functools.wraps(fn)
 361     def wrapped(*args, **kwargs):
 362         return decorator(fn(action(*args, **kwargs)))
 363
 364     return wrapped
 365
 366
 367 def decorate(decorator, fn):
 368     """Decorate the result of `fn` with `action`"""
 369
 370     @functools.wraps(fn)
 371     def decorated(*args, **kwargs):
 372         return decorator(fn(*args, **kwargs))
 373
 374     return decorated
 375
 376
 377 def getenv(name, default=None):
 378     return decode(os.getenv(name, default))
 379
 380
 381 def guess_mimetype(filename):
 382     """Robustly guess a filename's mimetype"""
 383     mimetype = None
 384     try:
 385         mimetype = mimetypes.guess_type(filename)[0]
 386     except UnicodeEncodeError:
 387         mimetype = mimetypes.guess_type(encode(filename))[0]
 388     except (TypeError, ValueError):
 389         mimetype = mimetypes.guess_type(decode(filename))[0]
 390     return mimetype
 391
 392
 393 def xopen(path, mode='r', encoding=None):
 394     return open(mkpath(path, encoding=encoding), mode)
 395
 396
 397 def print_stdout(msg, linesep='\n'):
 398     msg = msg + linesep
 399     if PY2:
 400         msg = encode(msg, encoding=ENCODING)
 401     sys.stdout.write(msg)
 402
 403
 404 def print_stderr(msg, linesep='\n'):
 405     msg = msg + linesep
 406     if PY2:
 407         msg = encode(msg, encoding=ENCODING)
 408     sys.stderr.write(msg)
 409
 410
 411 def error(msg, status=EXIT_FAILURE, linesep='\n'):
 412     print_stderr(msg, linesep=linesep)
 413     sys.exit(status)
 414
 415
 416 @interruptable
 417 def node():
 418     return platform.node()
 419
 420
 421 abspath = wrap(mkpath, os.path.abspath, decorator=decode)
 422 chdir = wrap(mkpath, os.chdir)
 423 exists = wrap(mkpath, os.path.exists)
 424 expanduser = wrap(encode, os.path.expanduser, decorator=decode)
 425 if PY2:
 426     if hasattr(os, 'getcwdu'):
 427         # pylint: disable=no-member
 428         getcwd = os.getcwdu
 429     else:
 430         getcwd = decorate(decode, os.getcwd)
 431 else:
 432     getcwd = os.getcwd
 433
 434
 435 # NOTE: find_executable() is originally from the stdlib, but starting with
 436 # python3.7 the stdlib no longer bundles distutils.
 437 def _find_executable(executable, path=None):
 438     """Tries to find 'executable' in the directories listed in 'path'.
 439
 440     A string listing directories separated by 'os.pathsep'; defaults to
 441     os.environ['PATH'].  Returns the complete filename or None if not found.
 442     """
 443     if path is None:
 444         path = os.environ['PATH']
 445
 446     paths = path.split(os.pathsep)
 447     _, ext = os.path.splitext(executable)
 448
 449     if (sys.platform == 'win32') and (ext != '.exe'):
 450         executable = executable + '.exe'
 451
 452     if not os.path.isfile(executable):
 453         for p in paths:
 454             f = os.path.join(p, executable)
 455             if os.path.isfile(f):
 456                 # the file exists, we have a shot at spawn working
 457                 return f
 458         return None
 459
 460     return executable
 461
 462
 463 if PY2:
 464     find_executable = wrap(mkpath, _find_executable, decorator=decode)
 465 else:
 466     find_executable = wrap(decode, _find_executable, decorator=decode)
 467 isdir = wrap(mkpath, os.path.isdir)
 468 isfile = wrap(mkpath, os.path.isfile)
 469 islink = wrap(mkpath, os.path.islink)
 470 makedirs = wrap(mkpath, os.makedirs)
 471 try:
 472     readlink = wrap(mkpath, os.readlink, decorator=decode)
 473 except AttributeError:
 474
 475     def _readlink_noop(p):
 476         return p
 477
 478     readlink = _readlink_noop
 479
 480 realpath = wrap(mkpath, os.path.realpath, decorator=decode)
 481 relpath = wrap(mkpath, os.path.relpath, decorator=decode)
 482 stat = wrap(mkpath, os.stat)
 483 unlink = wrap(mkpath, os.unlink)
 484 walk = wrap(mkpath, os.walk)