Sanitize PEX_ROOT handling.

In the past, portions of the pex cache could be controlled individually
but this was no longer the case in practice nor was it desirable. Unify
all cache handling under the PEX_ROOT and deprecate `--cache-dir` to
codify the new single pex cache as the PEX_ROOT.

Also add best-effort support for always finding a a viable PEX_ROOT even
when the configured value is not writeable. In conjunction with
`--runtime-pex-root` this provides for both a Pex CLI and created PEXes
that should always work wrt having a viable PEX_ROOT but still display a
warning if a suboptimal alternate had to be used.

Fixes pex-tool#746
Fixes pex-tool#816
Fixes pex-tool#926

pex/bin/pex.py

@@ -13,6 +13,7 @@
 from optparse import OptionGroup, OptionParser, OptionValueError
 from textwrap import TextWrapper
 
+from pex import pex_warnings
 from pex.common import die, safe_delete, safe_mkdtemp
 from pex.interpreter import PythonInterpreter
 from pex.interpreter_constraints import (
@@ -170,17 +171,18 @@ def configure_clp_pex_resolution(parser):
 
   group.add_option(
       '--disable-cache',
-      action='callback',
-      dest='cache_dir',
-      callback=process_disable_cache,
+      dest='disable_cache',
+      default=False,
+      action='store_true',
       help='Disable caching in the pex tool entirely.')
 
   group.add_option(
       '--cache-dir',
       dest='cache_dir',
-      default='{pex_root}',
-      help='The local cache directory to use for speeding up requirement '
-           'lookups. [Default: ~/.pex]')
+      default=None,
+      help='DEPRECATED: Use --pex-root instead. '
+           'The local cache directory to use for speeding up requirement '
+           'lookups. [Default: {}]'.format(ENV.PEX_ROOT))
 
   group.add_option(
       '--wheel', '--no-wheel', '--no-use-wheel',
@@ -502,8 +504,9 @@ def configure_clp():
   parser.add_option(
       '--pex-root',
       dest='pex_root',
-      default=ENV.PEX_ROOT,
-      help='Specify the pex root used in this invocation of pex. [Default: %default]')
+      default=None,
+      help='Specify the pex root used in this invocation of pex. '
+           '[Default: {}]'.format(ENV.PEX_ROOT))
 
   parser.add_option(
       '--help-variables',
@@ -523,7 +526,7 @@ def _safe_link(src, dst):
   os.symlink(src, dst)
 
 
-def build_pex(reqs, options):
+def build_pex(reqs, options, cache=None):
   interpreters = None  # Default to the current interpreter.
 
   # NB: options.python and interpreter constraints cannot be used together.
@@ -607,7 +610,7 @@ def walk_and_do(fn, src_dir):
                                 platforms=options.platforms,
                                 indexes=indexes,
                                 find_links=options.find_links,
-                                cache=options.cache_dir,
+                                cache=cache,
                                 build=options.build,
                                 use_wheel=options.use_wheel,
                                 compile=options.compile,
@@ -637,11 +640,6 @@ def walk_and_do(fn, src_dir):
   return pex_builder
 
 
-def make_relative_to_root(path):
-  """Update options so that defaults are user relative to specified pex_root."""
-  return os.path.normpath(path.format(pex_root=ENV.PEX_ROOT))
-
-
 def transform_legacy_arg(arg):
   # inherit-path used to be a boolean arg (so either was absent, or --inherit-path)
   # Now it takes a string argument, so --inherit-path is invalid.
@@ -670,18 +668,35 @@ def main(args=None):
     args, cmdline = args, []
 
   options, reqs = parser.parse_args(args=args)
-  if options.python and options.interpreter_constraint:
-    die('The "--python" and "--interpreter-constraint" options cannot be used together.')
 
-  with ENV.patch(PEX_VERBOSE=str(options.verbosity),
-                 PEX_ROOT=options.pex_root) as patched_env:
+  if options.cache_dir:
+    pex_warnings.warn('The --cache-dir option is deprecated, use --pex-root instead.')
+    if options.pex_root and options.cache_dir != options.pex_root:
+      die('Both --cache-dir and --pex-root were passed with conflicting values. '
+          'Just set --pex-root.')
+
+  if options.disable_cache:
+    def warn_ignore_pex_root(set_via):
+      pex_warnings.warn('The pex root has been set via {via} but --disable-cache is also set. '
+                        'Ignoring {via} and disabling caches.'.format(via=set_via))
 
-    # Don't alter cache if it is disabled.
     if options.cache_dir:
-      options.cache_dir = make_relative_to_root(options.cache_dir)
+      warn_ignore_pex_root('--cache-dir')
+    elif options.pex_root:
+      warn_ignore_pex_root('--pex-root')
+    elif os.environ.get('PEX_ROOT'):
+      warn_ignore_pex_root('PEX_ROOT')
+
+    pex_root = safe_mkdtemp()
+  else:
+    pex_root = options.cache_dir or options.pex_root or ENV.PEX_ROOT
+
+  if options.python and options.interpreter_constraint:
+    die('The "--python" and "--interpreter-constraint" options cannot be used together.')
 
+  with ENV.patch(PEX_VERBOSE=str(options.verbosity), PEX_ROOT=pex_root) as patched_env:
     with TRACER.timed('Building pex'):
-      pex_builder = build_pex(reqs, options)
+      pex_builder = build_pex(reqs, options, cache=ENV.PEX_ROOT)
 
     pex_builder.freeze(bytecode_compile=options.compile)
     pex = PEX(pex_builder.path(),

pex/common.py

@@ -329,6 +329,27 @@ def chmod_plus_w(path):
   os.chmod(path, path_mode)
 
 
+def can_write_dir(path):
+  """Determines if the directory at path can be written to by the current process.
+
+  If the directory doesn't exist, determines if it can be created and thus written to.
+
+  N.B.: This is a best-effort check only that uses permission heuristics and does not actually test
+  that the directory can be written to with and writes.
+
+  :param str path: The directory path to test.
+  :return: `True` if the given path is a directory that can be written to by the current process.
+  :rtype boo:
+  """
+  while not os.access(path, os.F_OK):
+    parent_path = os.path.dirname(path)
+    if not parent_path or (parent_path == path):
+      # We've recursed up to the root without success, which shouldn't happen,
+      return False
+    path = parent_path
+  return os.path.isdir(path) and os.access(path, os.R_OK | os.W_OK | os.X_OK)
+
+
 def touch(file, times=None):
   """Equivalent of unix `touch path`.
 

pex/pex_bootstrapper.py

@@ -233,7 +233,7 @@ def maybe_reexec_pex(compatibility_constraints=None):
 def _bootstrap(entry_point):
   from .pex_info import PexInfo
   pex_info = PexInfo.from_pex(entry_point)
-  pex_warnings.configure_warnings(pex_info)
+  pex_warnings.configure_warnings(pex_info, ENV)
   return pex_info
 
 

pex/pex_info.py

@@ -7,7 +7,7 @@
 import os
 
 from pex import pex_warnings
-from pex.common import open_zip
+from pex.common import can_write_dir, open_zip, safe_mkdtemp
 from pex.compatibility import PY2
 from pex.compatibility import string as compatibility_string
 from pex.orderedset import OrderedSet
@@ -295,7 +295,14 @@ def always_write_cache(self, value):
 
   @property
   def pex_root(self):
-    return os.path.expanduser(self._pex_info.get('pex_root', os.path.join('~', '.pex')))
+    pex_root = os.path.expanduser(self._pex_info.get('pex_root', os.path.join('~', '.pex')))
+    if not can_write_dir(pex_root):
+      tmp_root = safe_mkdtemp()
+      pex_warnings.warn('PEX_ROOT is configured as {pex_root} but that path is un-writeable, '
+                        'falling back to a temporary PEX_ROOT of {tmp_root} which will hurt '
+                        'performance.'.format(pex_root=pex_root, tmp_root=tmp_root))
+      pex_root = self._pex_info['pex_root'] = tmp_root
+    return pex_root
 
   @pex_root.setter
   def pex_root(self, value):

pex/pex_warnings.py

@@ -6,15 +6,12 @@
 
 import warnings
 
-from pex.variables import ENV
-
 
 class PEXWarning(Warning):
   """Indicates a warning from PEX about suspect buildtime or runtime configuration."""
 
 
-def configure_warnings(pex_info, env=None):
-  env = env or ENV
+def configure_warnings(pex_info, env):
   if env.PEX_VERBOSE > 0:
     emit_warnings = True
   elif env.PEX_EMIT_WARNINGS is not None:

pex/pip.py

@@ -79,7 +79,7 @@ def _spawn_pip_isolated(self, args, cache=None, interpreter=None):
       pip_args.append('--no-cache-dir')
 
     command = pip_args + args
-    with ENV.strip().patch(PEX_ROOT=ENV.PEX_ROOT, PEX_VERBOSE=str(pex_verbosity)) as env:
+    with ENV.strip().patch(PEX_ROOT=cache or ENV.PEX_ROOT, PEX_VERBOSE=str(pex_verbosity)) as env:
       # Guard against API calls from environment with ambient PYTHONPATH preventing pip PEX
       # bootstrapping. See: https://github.com/pantsbuild/pex/issues/892
       pythonpath = env.pop('PYTHONPATH', None)

pex/variables.py

@@ -10,7 +10,8 @@
 import sys
 from contextlib import contextmanager
 
-from pex.common import die
+from pex import pex_warnings
+from pex.common import can_write_dir, die, safe_mkdtemp
 
 __all__ = ('ENV', 'Variables')
 
@@ -269,7 +270,20 @@ def PEX_ROOT(self):
     The directory location for PEX to cache any dependencies and code.  PEX must write
     not-zip-safe eggs and all wheels to disk in order to activate them.  Default: ~/.pex
     """
-    return self._get_path('PEX_ROOT', default=os.path.expanduser('~/.pex'))
+    pex_root = self._get_path('PEX_ROOT', default=os.path.expanduser('~/.pex'))
+
+    if pex_root is None:
+      # PEX_ROOT is no set and we're running in stripped_defaults mode.
+      return None
+
+    if not can_write_dir(pex_root):
+      tmp_root = safe_mkdtemp()
+      pex_warnings.warn('PEX_ROOT is configured as {pex_root} but that path is un-writeable, '
+                        'falling back to a temporary PEX_ROOT of {tmp_root} which will hurt '
+                        'performance.'.format(pex_root=pex_root, tmp_root=tmp_root))
+      pex_root = self._environ['PEX_ROOT'] = tmp_root
+
+    return pex_root
 
   @property
   def PEX_PATH(self):

tests/test_common.py

@@ -13,6 +13,7 @@
     Chroot,
     PermPreservingZipFile,
     atomic_directory,
+    can_write_dir,
     chmod_plus_x,
     temporary_dir,
     touch
@@ -178,3 +179,27 @@ def test_chroot_perms_link_cross_device():
     mock_link.side_effect = OSError(expected_errno, os.strerror(expected_errno))
 
     assert_chroot_perms(Chroot.link)
+
+
+def test_can_write_dir_writeable_perms():
+  with temporary_dir() as writeable:
+    assert can_write_dir(writeable)
+
+    path = os.path.join(writeable, 'does/not/exist/yet')
+    assert can_write_dir(path)
+    touch(path)
+    assert not can_write_dir(path), 'Should not be able to write to a file.'
+
+
+def test_can_write_dir_unwriteable_perms():
+  with temporary_dir() as writeable:
+    no_perms_path = os.path.join(writeable, 'no_perms')
+    os.mkdir(no_perms_path, 0o444)
+    assert not can_write_dir(no_perms_path)
+
+    path_that_does_not_exist_yet = os.path.join(no_perms_path, 'does/not/exist/yet')
+    assert not can_write_dir(path_that_does_not_exist_yet)
+
+    os.chmod(no_perms_path, 0o744)
+    assert can_write_dir(no_perms_path)
+    assert can_write_dir(path_that_does_not_exist_yet)

tests/test_integration.py

@@ -15,7 +15,7 @@
 
 import pytest
 
-from pex.common import safe_copy, safe_mkdir, safe_open, safe_sleep, temporary_dir
+from pex.common import safe_copy, safe_mkdir, safe_open, safe_rmtree, safe_sleep, temporary_dir
 from pex.compatibility import WINDOWS, nested, to_bytes
 from pex.pex_info import PexInfo
 from pex.pip import get_pip
@@ -39,7 +39,7 @@
     temporary_content
 )
 from pex.third_party import pkg_resources
-from pex.util import named_temporary_file
+from pex.util import DistributionHelper, named_temporary_file
 
 
 def make_env(**kwargs):
@@ -1727,3 +1727,79 @@ def test_pex_run_strip_env():
     assert pex_env == json.loads(subprocess.check_output([unstripped_pex_file], env=env)), (
       'Expected the entrypoint environment to be left un-stripped.'
     )
+
+
+def iter_distributions(pex_root, project_name=None):
+  found = set()
+  for root, dirs, _ in os.walk(pex_root):
+    for d in dirs:
+      if project_name and not d.startswith(project_name):
+        continue
+      if not d.endswith('.whl'):
+        continue
+      wheel_path = os.path.realpath(os.path.join(root, d))
+      if wheel_path in found:
+        continue
+      dist = DistributionHelper.distribution_from_path(wheel_path)
+      if dist.project_name == project_name:
+        found.add(wheel_path)
+        yield dist
+
+
+def test_pex_cache_dir_and_pex_root():
+  python = ensure_python_interpreter(PY36)
+  with temporary_dir() as td:
+    cache_dir = os.path.join(td, 'cache_dir')
+    pex_root = os.path.join(td, 'pex_root')
+
+    # When the options both have the same value it should be accepted.
+    pex_file = os.path.join(td, 'pex_file')
+    run_pex_command(
+      python=python,
+      args=[
+        '--cache-dir', cache_dir,
+        '--pex-root', cache_dir,
+        'p537==1.0.3',
+        '-o', pex_file
+      ]
+    ).assert_success()
+
+    dists = list(iter_distributions(pex_root=cache_dir, project_name='p537'))
+    assert 1 == len(dists), (
+      'Expected to find exactly one distribution, found {}'.format(dists)
+    )
+
+    for directory in cache_dir, pex_root:
+      safe_rmtree(directory)
+
+    # When the options have conflicting values they should be rejected.
+    run_pex_command(
+      python=python,
+      args=[
+        '--cache-dir', cache_dir,
+        '--pex-root', pex_root,
+        'p537==1.0.3',
+        '-o', pex_file
+      ]
+    ).assert_failure()
+
+    assert not os.path.exists(cache_dir)
+    assert not os.path.exists(pex_root)
+
+
+def test_disable_cache():
+  python = ensure_python_interpreter(PY36)
+  with temporary_dir() as td:
+    pex_root = os.path.join(td, 'pex_root')
+    pex_file = os.path.join(td, 'pex_file')
+    run_pex_command(
+      python=python,
+      args=[
+        '--disable-cache',
+        'p537==1.0.3',
+        '-o', pex_file
+      ],
+      env=make_env(PEX_ROOT=pex_root)
+    ).assert_success()
+
+    assert not os.path.exists(pex_root)