Improve creation of error messages

src/Tools/tool_helper/src/lib.rs

@@ -7,6 +7,20 @@ pub type BufferedInputFile = BufReader<std::fs::File>;
 pub type Output            = Box<dyn Write>;
 pub type Input             = Box<dyn Read>;
 
+#[macro_export]
+macro_rules! construct_from_error_if {
+    ($result:expr, $format_text:literal) => {
+        tool_helper::callback_if_error($result, |error_text| {
+            format!($format_text, error_text=error_text)
+        })
+    };
+    ($result:expr, $format_text:literal, $($arg:expr)*) => {
+        tool_helper::callback_if_error($result, |error_text| {
+            format!($format_text, $($arg),*, error_text=error_text)
+        })
+    };
+}
+
 pub trait ErrorString {
     fn to_string(self) -> String;
 }
@@ -101,6 +115,30 @@ impl<T: ErrorString> std::convert::From<T> for Error {
     }
 }
 
+pub fn prefix_if_error<T>(prefix: &str, result: Result<T, Error>) -> Result<T, Error> {
+    match result {
+        Ok(value)      => Ok(value),
+        Err(mut error) => {
+            let mut new_text = String::from(prefix);
+
+            new_text.push_str(error.text.as_str());
+            error.text = new_text;
+            Err(error)
+        },
+    }
+}
+
+pub fn callback_if_error<F: Fn(String) -> String, T>(result: Result<T, Error>, callback: F) -> Result<T, Error> {
+    match result {
+        Ok(value)      => Ok(value),
+        Err(mut error) => {
+            error.text = callback(error.text);
+
+            Err(error)
+        }
+    }
+}
+
 pub fn open_output_file(output_path: &PathBuf) -> Result<BufWriter<std::fs::File>, Error> {
     Ok(std::io::BufWriter::new(std::fs::File::create(output_path)?))
 }