#25474 Added read-only warnings when saving documents (#25532)

* #25474 Added read-only warnings when saving documents

Block saving a file and notify user if windows is unable to save to the file for any reason, or the read-only attribute is checked. Also check std::filesystem::perms for write permission and other checks in FileInfo::isWritable(), although it doesn't seem to matter on windows.

Co-authored-by: Chris Hennes <chennes@pioneerlibrarysystem.org>

src/App/Document.cpp

@@ -1792,6 +1792,12 @@ bool Document::saveToFile(const char* filename) const
     // realpath is canonical filename i.e. without symlink
     std::string nativePath = canonical_path(filename);
 
+    // check if file is writeable, then block the save if it is not.
+    Base::FileInfo originalFileInfo(nativePath);
+    if (originalFileInfo.exists() && !originalFileInfo.isWritable()) {
+        throw Base::FileException("Unable to save document because file is marked as read-only or write permission is not available.", originalFileInfo);
+    }
+
     // make a tmp. file where to save the project data first and then rename to
     // the actual file name. This may be useful if overwriting an existing file
     // fails so that the data of the work up to now isn't lost.

src/Base/FileInfo.cpp

@@ -336,6 +336,44 @@ bool FileInfo::isWritable() const
     if (fs::is_directory(path)) {
         return directoryIsWritable(path);
     }
+#ifdef FC_OS_WIN32
+    // convert filename from UTF-8 to windows WSTRING
+    std::wstring fileNameWstring = toStdWString();
+    // requires import of <windows.h>
+    DWORD attributes = GetFileAttributes(fileNameWstring.c_str());
+    if (attributes == INVALID_FILE_ATTRIBUTES) {
+        // Log the error?
+        std::clog << "GetFileAttributes failed for file: " << FileName << '\n';
+        // usually indicates some kind of network file issue, so the file is probably not writable
+        return false;
+    }
+    if ((attributes & FILE_ATTRIBUTE_READONLY) != 0) {
+        return false;
+    }
+    // TEST if file is truly writable, because windows ACL does not map well to POSIX perms,
+    //  and there are other potential blockers (app or shared file locks, etc)
+    HANDLE hFile = CreateFileW(
+        fileNameWstring.c_str(),
+        GENERIC_WRITE,
+        0,  // ----> no sharing: fail if anyone else has it open
+        nullptr,
+        OPEN_EXISTING,
+        FILE_ATTRIBUTE_NORMAL,
+        nullptr
+    );
+
+    if (hFile == INVALID_HANDLE_VALUE) {
+        DWORD err = GetLastError();
+        if (err == ERROR_SHARING_VIOLATION || err == ERROR_LOCK_VIOLATION) {
+            return false;
+        }
+        return false;
+    }
+    if (!CloseHandle(hFile)) {
+        std::clog << "CloseHandle failed for file: " << FileName
+                  << " while checking for write access." << '\n';
+    }
+#endif
     fs::file_status stat = fs::status(path);
     fs::perms perms = stat.permissions();
     return (perms & fs::perms::owner_write) == fs::perms::owner_write;