Report errors in file input/output operations (#137)

Throw `std::filesystem::filesystem_error` from `file::read`, `file::write` and `file::append`

Author: bugdea1er

include/tmp/file

@@ -74,14 +74,17 @@ public:
 
   /// Reads the entire contents of this file
   /// @returns A string with this file contents
+  /// @throws std::filesystem::filesystem_error if cannot read the file contents
   std::string read() const;
 
   /// Writes the given content to this file discarding any previous content
   /// @param content   A string to write to this file
+  /// @throws std::filesystem::filesystem_error if cannot write to the file
   void write(std::string_view content) const;
 
   /// Appends the given content to the end of this file
   /// @param content   A string to append to this file
+  /// @throws std::filesystem::filesystem_error if cannot append to the file
   void append(std::string_view content) const;
 
   /// Returns the input stream to this file

src/file.cpp

@@ -91,16 +91,36 @@ file file::copy(const fs::path& path, std::string_view label,
 }
 
 std::string file::read() const {
-  std::ifstream stream = input_stream();
-  return std::string(std::istreambuf_iterator<char>(stream), {});
+  try {
+    std::ifstream stream = input_stream();
+    stream.exceptions(std::ifstream::failbit | std::ifstream::badbit);
+
+    return std::string(std::istreambuf_iterator(stream), {});
+  } catch (const std::ios::failure& err) {
+    throw fs::filesystem_error("Cannot read a temporary file", err.code());
+  }
 }
 
 void file::write(std::string_view content) const {
-  output_stream(std::ios::trunc) << content;
+  try {
+    std::ofstream stream = output_stream(std::ios::trunc);
+    stream.exceptions(std::ifstream::failbit | std::ifstream::badbit);
+
+    stream << content;
+  } catch (const std::ios::failure& err) {
+    throw fs::filesystem_error("Cannot write to a temporary file", err.code());
+  }
 }
 
 void file::append(std::string_view content) const {
-  output_stream(std::ios::app) << content;
+  try {
+    std::ofstream stream = output_stream(std::ios::app);
+    stream.exceptions(std::ifstream::failbit | std::ifstream::badbit);
+
+    stream << content;
+  } catch (const std::ios::failure& err) {
+    throw fs::filesystem_error("Cannot write to a temporary file", err.code());
+  }
 }
 
 std::ifstream file::input_stream() const {

tests/file.cpp

@@ -130,6 +130,14 @@ TEST(file, read_text) {
   EXPECT_EQ(tmpfile.read(), "Hello,\nworld!\n");
 }
 
+/// Tests file reading error reporting
+TEST(file, read_error) {
+  file tmpfile = file();
+  fs::remove(tmpfile);
+
+  EXPECT_THROW(tmpfile.read(), fs::filesystem_error);
+}
+
 /// Tests binary file writing
 TEST(file, write_binary) {
   file tmpfile = file();
@@ -178,6 +186,15 @@ TEST(file, write_text) {
   }
 }
 
+/// Tests file writing error reporting
+TEST(file, write_error) {
+  file tmpfile = file();
+  fs::permissions(tmpfile.path(), fs::perms::none);
+
+  EXPECT_THROW(tmpfile.write("Hello!"), fs::filesystem_error);
+  fs::permissions(tmpfile.path(), fs::perms::all);
+}
+
 /// Tests binary file appending
 TEST(file, append_binary) {
   file tmpfile = file();
@@ -230,6 +247,15 @@ TEST(file, append_text) {
   }
 }
 
+/// Tests file appending error reporting
+TEST(file, append_error) {
+  file tmpfile = file();
+  fs::permissions(tmpfile.path(), fs::perms::none);
+
+  EXPECT_THROW(tmpfile.append("world!"), fs::filesystem_error);
+  fs::permissions(tmpfile.path(), fs::perms::all);
+}
+
 /// Tests binary file reading from input_stream
 TEST(file, input_stream_binary) {
   file tmpfile = file();