Enable Python integration tests on Windows

Now that we have both a Python 2 and 3 interpreter on our CI machines (bazelbuild/continuous-integration#578), we can turn on these version tests for Windows. Since there's no autodetecting toolchain for Windows yet (bazelbuild#7844) we define an explicit toolchain.

Fixes bazelbuild#8411.

RELNOTES: None
PiperOrigin-RevId: 250562174

src/test/shell/bazel/BUILD

@@ -720,10 +720,6 @@ sh_test(
         ":test-deps",
         "@bazel_tools//tools/bash/runfiles",
     ],
-    tags = [
-        # Disabled on windows and mac; see TODOs in the test suite.
-        "no_windows",
-    ],
 )
 
 sh_test(

src/test/shell/bazel/python_version_test.sh

@@ -52,11 +52,6 @@ case "$(uname -s | tr [:upper:] [:lower:])" in
 msys*)
   # As of 2018-08-14, Bazel on Windows only supports MSYS Bash.
   declare -r is_windows=true
-  # As of 2019-05-18, this test is disabled on Windows (via "no_windows" tag),
-  # so this code shouldn't even have run.
-  # TODO(#7844): Enable this test for Windows once our autodetecting toolchain
-  # works transparently for this platform.
-  fail "This test does not run on Windows."
   ;;
 *)
   declare -r is_windows=false
@@ -72,7 +67,7 @@ fi
 
 #### TESTS #############################################################
 
-# Sanity test that our environment setup above works.
+# Sanity test that our environment setup works.
 function test_can_run_py_binaries() {
   mkdir -p test
 
@@ -94,7 +89,6 @@ import platform
 print("I am Python " + platform.python_version_tuple()[0])
 EOF
   cp test/main2.py test/main3.py
-  chmod u+x test/main2.py test/main3.py
 
   bazel run //test:main2 \
       &> $TEST_log || fail "bazel run failed"
@@ -142,18 +136,23 @@ EOF
 }
 
 # Regression test for #5104. This test ensures that it's possible to use
-# --build_python_zip in combination with a py_runtime (as opposed to not using
-# a py_runtime, i.e., the legacy --python_path mechanism).
-#
-# Note that with --incompatible_use_python_toolchains flipped, we're always
-# using a py_runtime, so in that case this amounts to a test that
-# --build_python_zip works at all.
+# --build_python_zip in combination with an in-workspace runtime, as opposed to
+# with a system runtime or not using a py_runtime at all (the legacy
+# --python_path mechanism).
 #
 # The specific issue #5104 was caused by file permissions being lost when
 # unzipping runfiles, which led to an unexecutable runtime.
-function test_build_python_zip_works_with_py_runtime() {
+function test_build_python_zip_works_with_workspace_runtime() {
   mkdir -p test
 
+  # The runfiles interpreter is either a sh script or bat script depending on
+  # the current platform.
+  if "$is_windows"; then
+    INTERPRETER_FILE="mockpy.bat"
+  else
+    INTERPRETER_FILE="mockpy.sh"
+  fi
+
   cat > test/BUILD << EOF
 load("@bazel_tools//tools/python:toolchain.bzl", "py_runtime_pair")
 
@@ -164,7 +163,7 @@ py_binary(
 
 py_runtime(
     name = "mock_runtime",
-    interpreter = ":mockpy.sh",
+    interpreter = ":$INTERPRETER_FILE",
     python_version = "PY3",
 )
 
@@ -184,11 +183,17 @@ EOF
 # executes the Python code.
 print("I am pybin!")
 EOF
-  cat > test/mockpy.sh <<EOF
-#!/bin/bash
+  if "$is_windows"; then
+    cat > "test/$INTERPRETER_FILE" << EOF
+@ECHO I am mockpy!
+EOF
+  else
+    cat > "test/$INTERPRETER_FILE" << EOF
+#!/bin/sh
 echo "I am mockpy!"
 EOF
-  chmod u+x test/mockpy.sh
+    chmod u+x test/mockpy.sh
+  fi
 
   bazel run //test:pybin \
       --extra_toolchains=//test:mock_toolchain --build_python_zip \
@@ -197,6 +202,11 @@ EOF
 }
 
 function test_pybin_can_have_different_version_pybin_as_data_dep() {
+  # TODO(#8503): Fix this test for windows.
+  if "$is_windows"; then
+    return
+  fi
+
   mkdir -p test
 
   cat > test/BUILD << EOF
@@ -231,22 +241,22 @@ import platform
 
 print("Inner bin uses Python " + platform.python_version_tuple()[0])
 EOF
-  chmod u+x test/py2bin.py
   cp test/py2bin.py test/py3bin.py
 
   cat > test/py2bin_calling_py3bin.py << EOF
 import platform
 import subprocess
 from bazel_tools.tools.python.runfiles import runfiles
 
+print("Outer bin uses Python " + platform.python_version_tuple()[0])
+
 r = runfiles.Create()
 bin_path = r.Rlocation("$WORKSPACE_NAME/test/py3bin")
+assert bin_path is not None
 
-print("Outer bin uses Python " + platform.python_version_tuple()[0])
 subprocess.call([bin_path])
 EOF
   sed s/py3bin/py2bin/ test/py2bin_calling_py3bin.py > test/py3bin_calling_py2bin.py
-  chmod u+x test/py2bin_calling_py3bin.py test/py3bin_calling_py2bin.py
 
   EXPFLAG="--incompatible_allow_python_version_transitions=true \
 --incompatible_py3_is_default=false \
@@ -267,6 +277,11 @@ EOF
 }
 
 function test_shbin_can_have_different_version_pybins_as_data_deps() {
+  # Uses bash, disable on windows.
+  if "$is_windows"; then
+    return
+  fi
+
   mkdir -p test
 
   cat > test/BUILD << EOF
@@ -394,6 +409,11 @@ EOF
 }
 
 function test_can_build_same_target_for_both_versions_in_one_build() {
+  # Uses bash, disable on windows.
+  if "$is_windows"; then
+    return
+  fi
+
   mkdir -p test
 
   cat > test/BUILD << EOF

src/test/shell/integration/python_stub_test.sh

@@ -59,6 +59,10 @@ fi
 
 # Tests in this file do not actually start a Python interpreter, but plug in a
 # fake stub executable to serve as the "interpreter".
+#
+# Note that this means this suite cannot be used for tests of the actual stub
+# script under Windows, since the stub script never runs (the launcher uses the
+# mock interpreter rather than a system interpreter, see discussion in #7947).
 
 use_fake_python_runtimes_for_testsuite
 

src/test/shell/testenv.sh

@@ -19,6 +19,8 @@
 # TODO(bazel-team): This file is currently an append of the old testenv.sh and
 # test-setup.sh files. This must be cleaned up eventually.
 
+# TODO(bazel-team): Factor each test suite's is-this-windows setup check to use
+# this var instead, or better yet a common $IS_WINDOWS var.
 PLATFORM="$(uname -s | tr [:upper:] [:lower:])"
 
 function is_darwin() {
@@ -363,6 +365,54 @@ java_import(
 EOF
 }
 
+# If the current platform is Windows, defines a Python toolchain for our
+# Windows CI machines. Otherwise does nothing.
+#
+# Our Windows CI machines have Python 2 and 3 installed at C:\Python2 and
+# C:\Python3 respectively.
+#
+# Since the tools directory is not cleared between test cases, this only needs
+# to run once per suite. However, the toolchain must still be registered
+# somehow.
+#
+# TODO(#7844): Delete this custom (and machine-specific) test setup once we have
+# an autodetecting Python toolchain for Windows.
+function maybe_setup_python_windows_tools() {
+  if [[ ! $PLATFORM =~ msys ]]; then
+    return
+  fi
+
+  mkdir -p tools/python/windows
+  cat > tools/python/windows/BUILD << EOF
+load("@bazel_tools//tools/python:toolchain.bzl", "py_runtime_pair")
+
+py_runtime(
+  name = "py2_runtime",
+  interpreter_path = r"C:\Python2\python.exe",
+  python_version = "PY2",
+)
+
+py_runtime(
+  name = "py3_runtime",
+  interpreter_path = r"C:\Python3\python.exe",
+  python_version = "PY3",
+)
+
+py_runtime_pair(
+  name = "py_runtime_pair",
+  py2_runtime = ":py2_runtime",
+  py3_runtime = ":py3_runtime",
+)
+
+toolchain(
+  name = "py_toolchain",
+  toolchain = ":py_runtime_pair",
+  toolchain_type = "@bazel_tools//tools/python:toolchain_type",
+  target_compatible_with = ["@bazel_tools//platforms:windows"],
+)
+EOF
+}
+
 function setup_skylark_javatest_support() {
   setup_javatest_common
   grep -q "name = \"junit4-jars\"" third_party/BUILD \
@@ -402,6 +452,27 @@ EOF
 function write_workspace_file() {
   cat > WORKSPACE << EOF
 workspace(name = '$WORKSPACE_NAME')
+EOF
+
+  maybe_setup_python_windows_workspace
+}
+
+# If the current platform is Windows, registers our custom Windows Python
+# toolchain. Otherwise does nothing.
+#
+# Since this modifies the WORKSPACE file, it must be called between test cases.
+function maybe_setup_python_windows_workspace() {
+  if [[ ! $PLATFORM =~ msys ]]; then
+    return
+  fi
+
+  # --extra_toolchains has left-to-right precedence semantics, but the bazelrc
+  # is processed before the command line. This means that any matching
+  # toolchains added to the bazelrc will always take precedence over toolchains
+  # set up by test cases. Instead, we add the toolchain to WORKSPACE so that it
+  # has lower priority than whatever is passed on the command line.
+  cat >> WORKSPACE << EOF
+register_toolchains("//tools/python/windows:py_toolchain")
 EOF
 }
 
@@ -422,6 +493,8 @@ function create_new_workspace() {
     || ln -s "${langtools_path}"  third_party/java/jdk/langtools/javac-9+181-r4173-1.jar
 
   write_workspace_file
+
+  maybe_setup_python_windows_tools
 }