[7.2.0] Respect $XDG_CACHE_HOME if available for Bazel's output root on Linux and BSD

site/en/remote/output-directories.md

@@ -29,9 +29,10 @@ The solution that's currently implemented:
 * Bazel must be invoked from a directory containing a WORKSPACE file (the
  "_workspace directory_"), or a subdirectory thereof. It reports an error if it
  is not.
-* The _outputRoot_ directory defaults to `~/.cache/bazel` on Linux,
- `/private/var/tmp` on macOS, and on Windows it defaults to `%HOME%` if set,
- else `%USERPROFILE%` if set, else the result of calling
+* The _outputRoot_ directory defaults to `${XDG_CACHE_HOME}/bazel` (or
+ `~/.cache/bazel`, if the `XDG_CACHE_HOME` environment variable is not set) on
+ Linux, `/private/var/tmp` on macOS, and on Windows it defaults to `%HOME%` if
+ set, else `%USERPROFILE%` if set, else the result of calling
  `SHGetKnownFolderPath()` with the `FOLDERID_Profile` flag set. If the
  environment variable `$TEST_TMPDIR` is set, as in a test of Bazel itself,
  then that value overrides the default.

src/main/cpp/blaze_util_bsd.cc

@@ -60,17 +60,24 @@ namespace blaze {
 using blaze_util::GetLastErrorString;
 using std::string;
 
+// ${XDG_CACHE_HOME}/bazel, a.k.a. ~/.cache/bazel by default (which is the
+// fallback when XDG_CACHE_HOME is not set)
 string GetOutputRoot() {
- char buf[2048];
- struct passwd pwbuf;
- struct passwd *pw = nullptr;
- int uid = getuid();
- int r = getpwuid_r(uid, &pwbuf, buf, 2048, &pw);
- if (r == 0 && pw != nullptr) {
- return blaze_util::JoinPath(pw->pw_dir, ".cache/bazel");
- } else {
- return "/tmp";
+ string xdg_cache_home = GetPathEnv("XDG_CACHE_HOME");
+ if (xdg_cache_home.empty()) {
+ char buf[2048];
+ struct passwd pwbuf;
+ struct passwd *pw = nullptr;
+ int uid = getuid();
+ int r = getpwuid_r(uid, &pwbuf, buf, 2048, &pw);
+ if (r == 0 && pw != nullptr) {
+ xdg_cache_home = blaze_util::JoinPath(pw->pw_dir, ".cache");
+ } else {
+ return "/tmp";
+ }
  }
+
+ return blaze_util::JoinPath(xdg_cache_home, "bazel");
 }
 
 void WarnFilesystemType(const blaze_util::Path &output_base) {

src/main/cpp/blaze_util_linux.cc

@@ -43,27 +43,29 @@ using blaze_util::GetLastErrorString;
 using std::string;
 using std::vector;
 
+// ${XDG_CACHE_HOME}/bazel, a.k.a. ~/.cache/bazel by default (which is the
+// fallback when XDG_CACHE_HOME is not set)
 string GetOutputRoot() {
- string base;
- string home = GetHomeDir();
- if (!home.empty()) {
- base = home;
- } else {
- char buf[2048];
- struct passwd pwbuf;
- struct passwd *pw = nullptr;
- int uid = getuid();
- int r = getpwuid_r(uid, &pwbuf, buf, 2048, &pw);
- if (r == 0 && pw != nullptr) {
- base = pw->pw_dir;
+ string xdg_cache_home = GetPathEnv("XDG_CACHE_HOME");
+ if (xdg_cache_home.empty()) {
+ string home = GetHomeDir(); // via $HOME env variable
+ if (home.empty()) {
+ // Fall back to home dir from password database
+ char buf[2048];
+ struct passwd pwbuf;
+ struct passwd *pw = nullptr;
+ int uid = getuid();
+ int r = getpwuid_r(uid, &pwbuf, buf, 2048, &pw);
+ if (r == 0 && pw != nullptr) {
+ home = pw->pw_dir;
+ } else {
+ return "/tmp";
+ }
  }
+ xdg_cache_home = blaze_util::JoinPath(home, ".cache");
  }
 
- if (!base.empty()) {
- return blaze_util::JoinPath(base, ".cache/bazel");
- }
-
- return "/tmp";
+ return blaze_util::JoinPath(xdg_cache_home, "bazel");
 }
 
 void WarnFilesystemType(const blaze_util::Path &output_base) {

src/test/cpp/startup_options_test.cc

@@ -92,15 +92,27 @@ TEST_F(StartupOptionsTest, JavaLoggingOptions) {
 #ifdef __linux
 TEST_F(StartupOptionsTest, OutputRootPreferTestTmpdirIfSet) {
  SetEnv("HOME", "/nonexistent/home");
+ SetEnv("XDG_CACHE_HOME", "/nonexistent/cache");
  SetEnv("TEST_TMPDIR", "/nonexistent/tmpdir");
  ReinitStartupOptions();
 
  ASSERT_EQ("/nonexistent/tmpdir", startup_options_->output_root);
 }
 
+TEST_F(StartupOptionsTest,
+ OutputRootPreferXdgCacheHomeIfSetAndTestTmpdirUnset) {
+ SetEnv("HOME", "/nonexistent/home");
+ SetEnv("XDG_CACHE_HOME", "/nonexistent/cache");
+ UnsetEnv("TEST_TMPDIR");
+ ReinitStartupOptions();
+
+ ASSERT_EQ("/nonexistent/cache/bazel", startup_options_->output_root);
+}
+
 TEST_F(StartupOptionsTest, OutputRootUseHomeDirectory) {
  SetEnv("HOME", "/nonexistent/home");
  UnsetEnv("TEST_TMPDIR");
+ UnsetEnv("XDG_CACHE_HOME");
  ReinitStartupOptions();
 
  ASSERT_EQ("/nonexistent/home/.cache/bazel", startup_options_->output_root);