Fix python stub template for python3 on Windows

1. Adding UNC prefix after os.path.join, so that paths will be normalized
and absolute.

2. Make example/py_native/bin.py work in python3

3. Add a shell test for building python binary with python3

4. Run all tests in batch mode

Fix https://github.com/bazelbuild/bazel/issues/2708

--
Change-Id: I8dc18c80ebba87e965fe6fef9978732e6c35b1f0
Reviewed-on: https://cr.bazel.build/9456
PiperOrigin-RevId: 150734716
MOS_MIGRATED_REVID=150734716

3 files changed, 29 insertions, 8 deletions

diff --git a/examples/py_native/bin.py b/examples/py_native/bin.py
index 7b656278f6..45c68b26e5 100644
--- a/examples/py_native/bin.py
+++ b/examples/py_native/bin.py
@@ -1,6 +1,7 @@
+# pylint: disable=superfluous-parens
 """A tiny example binary for the native Python rules of Bazel."""
 from examples.py_native.lib import GetNumber
 from fib import Fib
 
-print "The number is %d" % GetNumber()
-print "Fib(5) == %d" % Fib(5)
+print("The number is %d" % GetNumber())
+print("Fib(5) == %d" % Fib(5))
diff --git a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/stub_template.txt b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/stub_template.txt
index 0e28ce16f7..3951f49068 100644
--- a/src/main/java/com/google/devtools/build/lib/bazel/rules/python/stub_template.txt
+++ b/src/main/java/com/google/devtools/build/lib/bazel/rules/python/stub_template.txt
@@ -13,10 +13,13 @@ def IsWindows():
   return os.name == 'nt'
 
 def GetWindowsPathWithUNCPrefix(path):
-  """Changes the path, so that it uses unicode Windows paths"""
+  """
+  Adding UNC prefix after getting a normalized absolute Windows path,
+  it's no-op for non-Windows platforms or if running under python2.
+  """
   path = path.strip()
 
-  # No need to add prefix for non-Windows platforms,
+  # No need to add prefix for non-Windows platforms.
   # And \\?\ doesn't work in python 2
   if not IsWindows() or sys.version_info[0] < 3:
     return path
@@ -26,6 +29,7 @@ def GetWindowsPathWithUNCPrefix(path):
   if path.startswith(unicode_prefix):
     return path
 
+  # os.path.abspath returns a normalized absolute path
   return unicode_prefix + os.path.abspath(path)
 
 PYTHON_BINARY = '%python_binary%'
@@ -93,10 +97,8 @@ def FindModuleSpace():
 def CreateModuleSpace():
   ZIP_RUNFILES_DIRECTORY_NAME = "runfiles"
   temp_dir = tempfile.mkdtemp("", "Bazel.runfiles_")
-  # mkdtemp return absolute name
-  temp_dir = GetWindowsPathWithUNCPrefix(temp_dir)
   zf = zipfile.ZipFile(GetWindowsPathWithUNCPrefix(os.path.dirname(__file__)))
-  zf.extractall(temp_dir)
+  zf.extractall(GetWindowsPathWithUNCPrefix(temp_dir))
   return os.path.join(temp_dir, ZIP_RUNFILES_DIRECTORY_NAME)
 
 # Returns repository roots to add to the import path.
@@ -120,6 +122,8 @@ def Main():
   python_path_entries = CreatePythonPathEntries(python_imports, module_space)
   python_path_entries += GetRepositoriesImports(module_space, %import_all%)
 
+  python_path_entries = [GetWindowsPathWithUNCPrefix(d) for d in python_path_entries]
+
   old_python_path = os.environ.get('PYTHONPATH')
   python_path = os.pathsep.join(python_path_entries)
   if old_python_path:
@@ -138,6 +142,7 @@ def Main():
     rel_path = rel_path.replace("/", os.sep)
 
   main_filename = os.path.join(module_space, rel_path)
+  main_filename = GetWindowsPathWithUNCPrefix(main_filename)
   assert os.path.exists(main_filename), \
          'Cannot exec() %r: file not found.' % main_filename
   assert os.access(main_filename, os.R_OK), \
diff --git a/src/test/shell/bazel/bazel_windows_example_test.sh b/src/test/shell/bazel/bazel_windows_example_test.sh
index 20c94fb5e5..7f6f739454 100755
--- a/src/test/shell/bazel/bazel_windows_example_test.sh
+++ b/src/test/shell/bazel/bazel_windows_example_test.sh
@@ -33,8 +33,11 @@ fi
 
 function set_up() {
   copy_examples
-  EXTRA_BAZELRC="build --cpu=x64_windows_msvc"
   setup_bazelrc
+  cat >>"$TEST_TMPDIR/bazelrc" <<EOF
+startup --batch
+build --cpu=x64_windows_msvc
+EOF
 }
 
 # An assertion that execute a binary from a sub directory (to test runfiles)
@@ -141,5 +144,17 @@ function test_native_python() {
   assert_test_fails //examples/py_native:fail
 }
 
+function test_native_python_with_python3() {
+  PYTHON3_PATH=${PYTHON3_PATH:-/c/Program Files/Anaconda3}
+  if [ ! -x "${PYTHON3_PATH}/python.exe" ]; then
+    warn "Python3 binary not found under $PYTHON3_PATH, please set PYTHON3_PATH correctly"
+  else
+    # Shutdown bazel to ensure python path get updated.
+    export BAZEL_PYTHON="${PYTHON3_PATH}/python.exe"
+    export PATH="${PYTHON3_PATH}:$PATH"
+    test_native_python
+  fi
+}
+
 run_suite "examples on Windows"