Bazel client, JNI, Windows: impl. CreateJunction

Implement a CreateJunction function in the Windows
JNI library. Also move a bit of code from
file_windows to the JNI library, where it is
(also) needed.

This implementation is an improved version of
`blaze_util::SymlinkDirectories` in
blaze_util_windows: this version handles Windows
paths as `name` and `target`, and performs more
validation (e.g. on the length of `target`), plus
has more comments explaining the logic. In a
subsequent change I'll start using this new
function in blaze_util_windows.

This method will also be helpful in tests: we will
no longer have to shell out to mklink.

See https://github.com/bazelbuild/bazel/issues/2107

--
Change-Id: I7e9b085fdc2ba47be83da5319bded02bd323e71b
Reviewed-on: https://cr.bazel.build/8892
PiperOrigin-RevId: 147585207
MOS_MIGRATED_REVID=147585207

2 files changed, 123 insertions, 3 deletions

diff --git a/src/test/native/BUILD b/src/test/native/BUILD
index bd3f90d40b..be04c76466 100644
--- a/src/test/native/BUILD
+++ b/src/test/native/BUILD
@@ -9,19 +9,28 @@ filegroup(
 )
 
 cc_test(
-    name = "windows_util_test",
+    name = "windows_jni_test",
+    size = "small",
     srcs = select({
-        "//src:windows": ["windows_util_test.cc"],
-        "//src:windows_msvc": ["windows_util_test.cc"],
+        "//src:windows": [
+            "windows_util_test.cc",
+            "windows_file_operations_test.cc",
+        ],
+        "//src:windows_msvc": [
+            "windows_util_test.cc",
+            "windows_file_operations_test.cc",
+        ],
         "//conditions:default": ["dummy_test.cc"],
     }),
     deps = select({
         "//src:windows": [
             "//src/main/native:windows_jni_lib",
+            "//src/test/cpp/util:windows_test_util",
             "//third_party:gtest",
         ],
         "//src:windows_msvc": [
             "//src/main/native:windows_jni_lib",
+            "//src/test/cpp/util:windows_test_util",
             "//third_party:gtest",
         ],
         "//conditions:default": [],
diff --git a/src/test/native/windows_file_operations_test.cc b/src/test/native/windows_file_operations_test.cc
new file mode 100644
index 0000000000..f3258a9a86
--- /dev/null
+++ b/src/test/native/windows_file_operations_test.cc
@@ -0,0 +1,111 @@
+// Copyright 2017 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.
+#include <stdlib.h>
+#include <string.h>
+#include <windows.h>
+
+#include <memory>  // unique_ptr
+#include <sstream>
+#include <string>
+
+#include "gtest/gtest.h"
+#include "src/main/native/windows_file_operations.h"
+#include "src/test/cpp/util/windows_test_util.h"
+
+#if !defined(COMPILER_MSVC) && !defined(__CYGWIN__)
+#error("This test should only be run on Windows")
+#endif  // !defined(COMPILER_MSVC) && !defined(__CYGWIN__)
+
+namespace windows_util {
+
+using blaze_util::DeleteAllUnder;
+using blaze_util::GetTestTmpDirW;
+using std::string;
+using std::unique_ptr;
+using std::wstring;
+
+static const wstring kUncPrefix = wstring(L"\\\\?\\");
+
+class WindowsFileOperationsTest : public ::testing::Test {
+ public:
+  void TearDown() override { DeleteAllUnder(GetTestTmpDirW()); }
+};
+
+TEST_F(WindowsFileOperationsTest, TestCreateJunction) {
+  wstring tmp(kUncPrefix + GetTestTmpDirW());
+  wstring target(tmp + L"\\junc_target");
+  EXPECT_TRUE(::CreateDirectoryW(target.c_str(), NULL));
+  wstring file1(target + L"\\foo");
+  EXPECT_TRUE(blaze_util::CreateDummyFile(file1));
+
+  EXPECT_EQ(IS_JUNCTION_NO, IsJunctionOrDirectorySymlink(target.c_str()));
+  EXPECT_NE(INVALID_FILE_ATTRIBUTES, ::GetFileAttributesW(file1.c_str()));
+
+  wstring name(tmp + L"\\junc_name");
+
+  // Create junctions from all combinations of UNC-prefixed or non-prefixed name
+  // and target paths.
+  ASSERT_EQ("", CreateJunction(name + L"1", target));
+  ASSERT_EQ("", CreateJunction(name + L"2", target.substr(4)));
+  ASSERT_EQ("", CreateJunction(name.substr(4) + L"3", target));
+  ASSERT_EQ("", CreateJunction(name.substr(4) + L"4", target.substr(4)));
+
+  // Assert creation of the junctions.
+  ASSERT_EQ(IS_JUNCTION_YES,
+            IsJunctionOrDirectorySymlink((name + L"1").c_str()));
+  ASSERT_EQ(IS_JUNCTION_YES,
+            IsJunctionOrDirectorySymlink((name + L"2").c_str()));
+  ASSERT_EQ(IS_JUNCTION_YES,
+            IsJunctionOrDirectorySymlink((name + L"3").c_str()));
+  ASSERT_EQ(IS_JUNCTION_YES,
+            IsJunctionOrDirectorySymlink((name + L"4").c_str()));
+
+  // Assert that the file is visible under all junctions.
+  ASSERT_NE(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"1\\foo").c_str()));
+  ASSERT_NE(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"2\\foo").c_str()));
+  ASSERT_NE(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"3\\foo").c_str()));
+  ASSERT_NE(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"4\\foo").c_str()));
+
+  // Assert that no other file exists under the junctions.
+  wstring file2(target + L"\\bar");
+  ASSERT_EQ(INVALID_FILE_ATTRIBUTES, ::GetFileAttributesW(file2.c_str()));
+  ASSERT_EQ(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"1\\bar").c_str()));
+  ASSERT_EQ(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"2\\bar").c_str()));
+  ASSERT_EQ(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"3\\bar").c_str()));
+  ASSERT_EQ(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"4\\bar").c_str()));
+
+  // Create a new file.
+  EXPECT_TRUE(blaze_util::CreateDummyFile(file2));
+  EXPECT_NE(INVALID_FILE_ATTRIBUTES, ::GetFileAttributesW(file2.c_str()));
+
+  // Assert that the newly created file appears under all junctions.
+  ASSERT_NE(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"1\\bar").c_str()));
+  ASSERT_NE(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"2\\bar").c_str()));
+  ASSERT_NE(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"3\\bar").c_str()));
+  ASSERT_NE(INVALID_FILE_ATTRIBUTES,
+            ::GetFileAttributesW((name + L"4\\bar").c_str()));
+}
+
+}  // namespace windows_util