6 files changed, 82 insertions, 1 deletions
diff --git a/src/main/cpp/util/path_platform.h b/src/main/cpp/util/path_platform.h
index 9653a676bb..3c4671f004 100644
--- a/src/main/cpp/util/path_platform.h
+++ b/src/main/cpp/util/path_platform.h
@@ -54,6 +54,16 @@ bool IsAbsolute(const std::string &path);
 //   MakeAbsolute("C:/foo") ---> "C:/foo"
 std::string MakeAbsolute(const std::string &path);
 
+// Returns the given path in absolute form, taking into account a possible
+// starting environment variable on the windows platform, so that we can
+// accept standard path variables like %USERPROFILE%. We do not support
+// unix-style envvars here: recreating that logic is error-prone and not
+// worthwhile, since they are less critical to standard paths as in Windows.
+//
+//   MakeAbsolute("foo") in wd "/bar" --> "/bar/foo"
+//   MakeAbsolute("%USERPROFILE%/foo") --> "C:\Users\bazel-user\foo"
+std::string MakeAbsoluteAndResolveWindowsEnvvars(const std::string &path);
+
 // TODO(bazel-team) consider changing the path(_platform) header split to be a
 // path.h and path_windows.h split, which would make it clearer what functions
 // are included by an import statement. The downside to this gain in clarity
diff --git a/src/main/cpp/util/path_posix.cc b/src/main/cpp/util/path_posix.cc
index 267dc22931..9c0b440d11 100644
--- a/src/main/cpp/util/path_posix.cc
+++ b/src/main/cpp/util/path_posix.cc
@@ -66,4 +66,9 @@ std::string MakeAbsolute(const std::string &path) {
 
   return JoinPath(blaze_util::GetCwd(), path);
 }
+
+std::string MakeAbsoluteAndResolveWindowsEnvvars(const std::string &path) {
+  return MakeAbsolute(path);
+}
+
 }  // namespace blaze_util
diff --git a/src/main/cpp/util/path_windows.cc b/src/main/cpp/util/path_windows.cc
index 041a0e847e..15dd0ddce6 100644
--- a/src/main/cpp/util/path_windows.cc
+++ b/src/main/cpp/util/path_windows.cc
@@ -14,6 +14,7 @@
 
 #include "src/main/cpp/util/path_platform.h"
 
+#include <assert.h>
 #include <wchar.h>  // wcslen
 #include <windows.h>
 
@@ -87,6 +88,32 @@ std::string MakeAbsolute(const std::string& path) {
       WstringToCstring(RemoveUncPrefixMaybe(wpath.c_str())).get());
 }
 
+std::string MakeAbsoluteAndResolveWindowsEnvvars(const std::string& path) {
+  // Get the size of the expanded string, so we know how big of a buffer to
+  // provide. The returned size includes the null terminator.
+  std::unique_ptr<CHAR[]> resolved(new CHAR[MAX_PATH]);
+  DWORD size =
+      ::ExpandEnvironmentStrings(path.c_str(), resolved.get(), MAX_PATH);
+  if (size == 0) {
+    BAZEL_DIE(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR)
+        << "MakeAbsoluteAndResolveWindowsEnvvars(" << path
+        << "): ExpandEnvironmentStrings failed: " << GetLastErrorString();
+  } else if (size > MAX_PATH) {
+    // Try again with a buffer bigger than MAX_PATH.
+    resolved.reset(new CHAR[size]);
+    DWORD second_size =
+        ::ExpandEnvironmentStrings(path.c_str(), resolved.get(), size);
+    if (second_size == 0) {
+      BAZEL_DIE(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR)
+          << "MakeAbsoluteAndResolveWindowsEnvvars(" << path
+          << "): ExpandEnvironmentStrings failed with second buffer: "
+          << GetLastErrorString();
+    }
+    assert(second_size <= size);
+  }
+  return MakeAbsolute(std::string(resolved.get()));
+}
+
 bool CompareAbsolutePaths(const std::string& a, const std::string& b) {
   return ConvertPath(a) == ConvertPath(b);
 }
diff --git a/src/test/cpp/util/BUILD b/src/test/cpp/util/BUILD
index 455994f3d9..1a86b0d0c6 100644
--- a/src/test/cpp/util/BUILD
+++ b/src/test/cpp/util/BUILD
@@ -60,6 +60,7 @@ cc_test(
     ] + select({
         "//src/conditions:windows": [
             ":windows_test_util",
+            "//src/main/cpp:blaze_util",
             "//src/main/native/windows:lib-file",
         ],
         "//conditions:default": [],
diff --git a/src/test/cpp/util/path_posix_test.cc b/src/test/cpp/util/path_posix_test.cc
index f1262cdda1..df79b59c1e 100644
--- a/src/test/cpp/util/path_posix_test.cc
+++ b/src/test/cpp/util/path_posix_test.cc
@@ -159,4 +159,15 @@ TEST(PathPosixTest, MakeAbsolute) {
   EXPECT_EQ(MakeAbsolute(""), "");
 }
 
+TEST(PathPosixTest, MakeAbsoluteAndResolveWindowsEnvvars) {
+  // Check that Unix-style envvars are not resolved.
+  EXPECT_EQ(MakeAbsoluteAndResolveWindowsEnvvars("$PATH"),
+            JoinPath(GetCwd(), "$PATH"));
+  EXPECT_EQ(MakeAbsoluteAndResolveWindowsEnvvars("${PATH}"),
+            JoinPath(GetCwd(), "${PATH}"));
+  // Check that Windows-style envvars are not resolved when not on Windows.
+  EXPECT_EQ(MakeAbsoluteAndResolveWindowsEnvvars("%PATH%"),
+            JoinPath(GetCwd(), "%PATH%"));
+}
+
 }  // namespace blaze_util
diff --git a/src/test/cpp/util/path_windows_test.cc b/src/test/cpp/util/path_windows_test.cc
index 15875603f7..c78c4ab012 100644
--- a/src/test/cpp/util/path_windows_test.cc
+++ b/src/test/cpp/util/path_windows_test.cc
@@ -20,6 +20,7 @@
 #include <string>
 
 #include "gtest/gtest.h"
+#include "src/main/cpp/blaze_util_platform.h"
 #include "src/main/cpp/util/file_platform.h"
 #include "src/main/cpp/util/path.h"
 #include "src/main/cpp/util/path_platform.h"
@@ -298,7 +299,7 @@ TEST(PathWindowsTest, ConvertPathTest) {
   EXPECT_EQ("c:\\foo\\bar", ConvertPath("c:/../foo\\BAR\\.\\"));
 }
 
-TEST(PathWindowsTest, TestMakeAbsolute) {
+TEST(PathWindowsTest, MakeAbsolute) {
   EXPECT_EQ("c:\\foo\\bar", MakeAbsolute("C:\\foo\\BAR"));
   EXPECT_EQ("c:\\foo\\bar", MakeAbsolute("C:/foo/bar"));
   EXPECT_EQ("c:\\foo\\bar", MakeAbsolute("C:\\foo\\bar\\"));
@@ -314,4 +315,30 @@ TEST(PathWindowsTest, TestMakeAbsolute) {
   EXPECT_EQ("", MakeAbsolute(""));
 }
 
+TEST(PathWindowsTest, MakeAbsoluteAndResolveWindowsEnvvars_WithTmpdir) {
+  // We cannot test the system-default paths like %ProgramData% because these
+  // are wiped from the test environment. TestTmpdir is set by Bazel though,
+  // so serves as a fine substitute.
+  char buf[MAX_PATH] = {0};
+  DWORD len = ::GetEnvironmentVariableA("TEST_TMPDIR", buf, MAX_PATH);
+  const std::string tmpdir = buf;
+  const std::string expected_tmpdir_bar = ConvertPath(tmpdir + "\\bar");
+
+  EXPECT_EQ(expected_tmpdir_bar,
+            MakeAbsoluteAndResolveWindowsEnvvars("%TEST_TMPDIR%\\bar"));
+  EXPECT_EQ(expected_tmpdir_bar,
+            MakeAbsoluteAndResolveWindowsEnvvars("%Test_Tmpdir%\\bar"));
+  EXPECT_EQ(expected_tmpdir_bar,
+            MakeAbsoluteAndResolveWindowsEnvvars("%test_tmpdir%\\bar"));
+  EXPECT_EQ(expected_tmpdir_bar,
+            MakeAbsoluteAndResolveWindowsEnvvars("%test_tmpdir%/bar"));
+}
+
+TEST(PathWindowsTest, MakeAbsoluteAndResolveWindowsEnvvars_LongPaths) {
+  const std::string long_path = "c:\\" + std::string(MAX_PATH, 'a');
+  blaze::SetEnv("long", long_path);
+
+  EXPECT_EQ(long_path, MakeAbsoluteAndResolveWindowsEnvvars("%long%"));
+}
+
 }  // namespace blaze_util