Replace whltool.par with whltool_wrapper.py

python/whl.bzl

@@ -44,7 +44,7 @@ whl_library = repository_rule(
         "extras": attr.string_list(),
         "_script": attr.label(
             executable = True,
-            default = Label("//tools:whltool.par"),
+            default = Label("//tools:whltool_wrapper.py"),
             cfg = "host",
         ),
     },

tools/piptool_wrapper.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-# Copyright 2017 The Bazel Authors. All rights reserved.
+# Copyright 2018 The Bazel Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -26,8 +26,6 @@
 import os
 import sys
 
-# Never do what we're about to do.
-#
 # Add our first-party source, and vendored third_party packages, to
 # the start of sys.path, so that we win any collision with already
 # installed modules.
@@ -56,6 +54,6 @@
 assert wheel.__version__ == '0.30.0'
 assert pip.__version__ == '9.0.1'
 
-# Invoke piptool
+# Invoke tool
 import piptool
 piptool.main()

tools/whltool_wrapper.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python
+
+# Copyright 2018 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Wrapper to invoke whl.py with vendored third-party dependencies.
+
+This wrapper must work under Python 2.7.*, or any Python 3.* >= 3.4.0.
+It must also work under Linux, Mac OS, Windows, and any other
+operating system.  It must work inside or outside a virtualenv, inside
+or outside a runfiles tree, and inside or outside a Bazel execroot.
+It must work with arbitrary other packages on the Python import path.
+"""
+
+import os
+import sys
+
+# Add our first-party source, and vendored third_party packages, to
+# the start of sys.path, so that we win any collision with already
+# installed modules.
+
+_this_file = __file__
+if (_this_file is None) or not os.path.isfile(_this_file):
+    sys.exit("whltool_wrapper.py failed.  Cannot determine __file__")
+
+_tool_dir = os.path.dirname(_this_file)
+_root_dir = os.path.abspath(os.path.join(_tool_dir, '..'))
+sys.path[0:0] = [
+    # Vendored third_party packages
+    os.path.join(_root_dir, 'third_party'),
+    # First party source (not a Python import package, just a directory)
+    os.path.join(_root_dir, 'rules_python'),
+    ]
+
+# Safe to import
+import setuptools
+import pkg_resources
+import wheel
+import pip
+
+# Sanity check that vendoring logic worked
+assert setuptools.__version__ == '38.5.1'
+assert wheel.__version__ == '0.30.0'
+assert pip.__version__ == '9.0.1'
+
+# Invoke tool
+import whl
+whl.main()