Merge and fix conflicts

tests/libslic3r/test_utils.cpp

@@ -2,6 +2,13 @@
 
 #include "libslic3r/Utils.hpp"
 
+#include "test_utils.hpp"
+
+#include <algorithm>
+#include <cctype>
+#include <fstream>
+#include <string>
+
 #ifndef _WIN32
 #include <unistd.h>     // getuid
 #endif
@@ -52,3 +59,32 @@ TEST_CASE("per-user temp root is unchanged on Windows, isolated elsewhere", "[ut
     REQUIRE_THAT(root, Catch::Matchers::StartsWith(base + "/orcaslicer_"));
 #endif
 }
+
+TEST_CASE("copy_file reports the OS error when the destination cannot be written", "[utils]") {
+    ScopedTemporaryFile source(".txt");
+    {
+        std::ofstream ofs(source.string(), std::ios::binary);
+        ofs << "orca";
+    }
+    REQUIRE(boost::filesystem::exists(source.path()));
+
+    // A directory that was never created, so the copy fails on every platform.
+    const boost::filesystem::path destination = source.path().parent_path() / "orca-missing-dir" / "copy.txt";
+    REQUIRE_FALSE(boost::filesystem::exists(destination.parent_path()));
+
+    std::string error_message;
+    REQUIRE(copy_file(source.string(), destination.string(), error_message) == FAIL_COPY_FILE);
+    REQUIRE_FALSE(error_message.empty());
+
+#ifdef _WIN32
+    // The Windows branch formats GetLastError() itself. Writing that as
+    // "Error: " + errCode adds an integer to a string literal, which indexes into the
+    // literal instead of appending and runs off its end for any code above 7.
+    const std::string prefix = "Error: ";
+    REQUIRE(error_message.rfind(prefix, 0) == 0);
+
+    const std::string code = error_message.substr(prefix.size());
+    REQUIRE_FALSE(code.empty());
+    REQUIRE(std::all_of(code.begin(), code.end(), [](unsigned char c) { return std::isdigit(c) != 0; }));
+#endif // _WIN32
+}