Add CI for Windows

.travis.yml

@@ -1,9 +1,9 @@
 x-tox-env: &x-tox-env >
-  TOX_CMD="tox --skip-missing-interpreters=false -v"
+  TOX_CMD="${TOX_PATH:-tox} --skip-missing-interpreters=false -v"
 
 x-tox-install: &x-tox-install |
-  pip install -U pip
-  pip install 'tox<=3.14.5' 'virtualenv<20.0.5'
+  ${PIP_PATH:-pip} install -U pip
+  ${PIP_PATH:-pip} install 'tox<=3.14.5' 'virtualenv<20.0.5'
 
 x-linux-shard: &x-linux-shard
   os: linux
@@ -51,6 +51,9 @@ x-pyenv-install: &x-pyenv-install |
   "${PYENV}" install --keep --skip-existing ${PYENV_VERSION}
   "${PYENV}" global ${PYENV_VERSION}
 
+x-pyenv-27-env: &x-pyenv-27-env >
+  PYENV_VERSION=2.7.18
+
 x-pyenv-39-env: &x-pyenv-39-env >
   PYENV_VERSION=3.9.1
 
@@ -89,7 +92,7 @@ x-osx-27-shard: &x-osx-27-shard
   env:
     - *x-tox-env
     - *x-pyenv-env
-    - PYENV_VERSION=2.7.18
+    - *x-pyenv-27-env
 
 x-osx-39-shard: &x-osx-39-shard
   <<: *x-osx-shard
@@ -98,6 +101,33 @@ x-osx-39-shard: &x-osx-39-shard
     - *x-pyenv-env
     - *x-pyenv-39-env
 
+x-windows-shard: &x-windows-shard
+  os: windows
+  language: shell
+  cache:
+    # The default is 3 minutes (180).
+    timeout: 300
+  install:
+    - *x-tox-install
+
+x-windows-27-shard: &x-windows-27-shard
+  <<: *x-windows-shard
+  before_install:
+  - choco install python2
+  env:
+    - PIP_PATH="C:\Python27\python.exe -m pip"
+    - TOX_PATH="C:\Python27\Scripts\tox"
+    - *x-tox-env
+
+x-windows-39-shard: &x-windows-39-shard
+  <<: *x-windows-shard
+  before_install:
+  - choco install python --version 3.9.1
+  env:
+    - PIP_PATH="C:\Python39\python.exe -m pip"
+    - TOX_PATH="C:\Python39\Scripts\tox"
+    - *x-tox-env
+
 # NB: Travis partitions caches using a combination of os, language amd env vars. As such, we do not
 # use TOXENV and instead pass the toxenv via -e on the command line. This helps ensure we share
 # caches as much as possible (eg: all linux python 2.7.15 shards share a cache).
@@ -177,3 +207,19 @@ matrix:
     - <<: *x-osx-39-shard
       name: TOXENV=py39-integration
       script: ${TOX_CMD} -e py39-integration
+
+    - <<: *x-windows-27-shard
+      name: TOXENV=py27
+      script: ${TOX_CMD} -e py27
+
+    - <<: *x-windows-39-shard
+      name: TOXENV=py39
+      script: ${TOX_CMD} -e py39
+
+    - <<: *x-windows-27-shard
+      name: TOXENV=py27-integration
+      script: ${TOX_CMD} -e py27-integration
+
+    - <<: *x-windows-39-shard
+      name: TOXENV=py39-integration
+      script: ${TOX_CMD} -e py39-integration

pex/common.py

@@ -6,7 +6,6 @@
 import atexit
 import contextlib
 import errno
-import fcntl
 import os
 import re
 import shutil
@@ -21,8 +20,14 @@
 from datetime import datetime
 from uuid import uuid4
 
+from pex.compatibility import WINDOWS
 from pex.typing import TYPE_CHECKING
 
+if WINDOWS:
+    import msvcrt
+else:
+    import fcntl
+
 if TYPE_CHECKING:
     from typing import Any, DefaultDict, Iterable, Iterator, NoReturn, Optional, Set, Sized
 
@@ -393,7 +398,10 @@ def unlock():
         if lock_fd is None:
             return
         try:
-            fcntl.lockf(lock_fd, fcntl.LOCK_UN)
+            if WINDOWS:
+                msvcrt.locking(lock_fd, msvcrt.LK_UNLCK, 1)
+            else:
+                fcntl.lockf(lock_fd, fcntl.LOCK_UN)
         finally:
             os.close(lock_fd)
 
@@ -410,7 +418,21 @@ def unlock():
         # N.B.: Since lockf operates on an open file descriptor and these are guaranteed to be
         # closed by the operating system when the owning process exits, this lock is immune to
         # staleness.
-        fcntl.lockf(lock_fd, fcntl.LOCK_EX)  # A blocking write lock.
+        if WINDOWS:
+            while True:
+                # Force the non-blocking lock to be blocking. LK_LOCK is msvcrt's implementation of
+                # a blocking lock, but it only tries 10 times, once per second before rasing an
+                # OSError.
+                try:
+                    msvcrt.locking(lock_fd, msvcrt.LK_LOCK, 1)
+                    break
+                except OSError as ex:
+                    # Deadlock error is raised after failing to lock the file
+                    if ex.errno != errno.EDEADLOCK:
+                        raise
+                    safe_sleep(1)
+        else:
+            fcntl.lockf(lock_fd, fcntl.LOCK_EX)  # A blocking write lock.
         if atomic_dir.is_finalized:
             # We lost the double-checked locking race and our work was done for us by the race
             # winner so exit early.