Test for output file permissions error

Author: WardBrian

make/tests

@@ -70,6 +70,7 @@ test/interface/multi_chain_test$(EXE):            $(call depends_on_test_models,
 test/interface/optimization_output_test$(EXE):    $(call depends_on_test_models, optimization_output simple_jacobian_model)
 test/interface/output_sig_figs_test$(EXE):        $(call depends_on_test_models, proper_sig_figs)
 test/interface/pathfinder_test$(EXE):             $(call depends_on_test_models, multi_normal_model eight_schools empty)
+test/interface/permissions_test$(EXE):            $(call depends_on_test_models, test_model)
 test/interface/print_uninitialized_test$(EXE):    $(call depends_on_test_models, print_uninitialized)
 test/interface/save_metric_json_test$(EXE):       $(call depends_on_test_models, simplex_model multi_normal_model)
 test/interface/variational_output_test$(EXE):     $(call depends_on_test_models, variational_output)

src/test/interface/permissions_test.cpp

@@ -0,0 +1,23 @@
+#include <cmdstan/stansummary_helper.hpp>
+#include <stan/io/stan_csv_reader.hpp>
+#include <stan/services/error_codes.hpp>
+#include <test/utility.hpp>
+#include <gtest/gtest.h>
+
+using cmdstan::test::convert_model_path;
+
+TEST(interface, unwritable_file) {
+  std::string model = convert_model_path(
+      std::vector{"src", "test", "test-models", "test_model"});
+  std::string output
+      = convert_model_path(std::vector{"test", "output_unwritable.csv"});
+
+  cmdstan::test::temporary_unwritable_file guard(output);
+
+  std::string command
+      = model + " sample num_warmup=1 num_samples=1 output file=" + output;
+
+  cmdstan::test::run_command_output out = cmdstan::test::run_command(command);
+  EXPECT_IN_STRING("Permission denied", out.output);
+  EXPECT_TRUE(out.hasError);
+}

src/test/utility.hpp

@@ -12,6 +12,7 @@
 #include <string>
 #include <vector>
 #include <sys/stat.h>
+#include <sys/types.h>
 
 #define EXPECT_IN_STRING(needle, haystack)                  \
   EXPECT_TRUE(boost::algorithm::contains(haystack, needle)) \
@@ -318,6 +319,47 @@ bool is_valid_JSON(std::string &text) {
   return !document.Parse<0>(text.c_str()).HasParseError();
 }
 
+namespace internal {
+
+// TODO: can be replaced with std::filesystem when we have better compiler
+// support for C++17 (currently missing from our minimum clang version)
+#ifdef _WIN32
+#include <io.h>
+void make_unwritable_file(const std::string &filename) {
+  _chmod(filename.c_str(), _S_IREAD);
+}
+void make_writable(const std::string &filename) {
+  _chmod(filename.c_str(), _S_IWRITE);
+}
+#else
+void make_unwritable(const std::string &filename) {
+  chmod(filename.c_str(), 0444);
+}
+void make_writable(const std::string &filename) {
+  chmod(filename.c_str(), 0644);
+}
+#endif
+
+}  // namespace internal
+
+struct temporary_unwritable_file {
+  std::string filename;
+  temporary_unwritable_file(const std::string &filename) : filename(filename) {
+    {
+      // this will create the file if it does not exist
+      std::ofstream ofs(filename);
+      ofs.close();
+    }
+    EXPECT_TRUE(file_exists(filename));
+    internal::make_unwritable(filename);
+  }
+  ~temporary_unwritable_file() noexcept(false) {
+    internal::make_writable(filename);
+    EXPECT_EQ(remove(filename.c_str()), 0);
+    EXPECT_FALSE(file_exists(filename));
+  }
+};
+
 }  // namespace test
 }  // namespace cmdstan
 #endif