feat: improve error message

malva/src/error.rs

@@ -4,21 +4,20 @@ use std::fmt::Display;
 #[derive(Clone, Debug)]
 pub enum Error {
     /// Error from the parser, usually related to syntax error.
-    Parser(raffia::error::Error),
+    /// The first component is the error type from Raffia,
+    /// and the second component is error line number,
+    /// and the third component is error column number.
+    Parser(raffia::error::Error, usize, usize),
 }
 
 impl Display for Error {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Error::Parser(error) => write!(f, "syntax error: {}", error.kind),
+            Error::Parser(error, line, col) => {
+                write!(f, "syntax error at line {line}, col {col}: {}", error.kind)
+            }
         }
     }
 }
 
 impl std::error::Error for Error {}
-
-impl From<raffia::error::Error> for Error {
-    fn from(error: raffia::error::Error) -> Self {
-        Error::Parser(error)
-    }
-}

malva/src/lib.rs

@@ -28,7 +28,10 @@ pub fn format_text(input: &str, syntax: Syntax, options: &FormatOptions) -> Resu
         .build();
     let stylesheet = match parser.parse::<Stylesheet>() {
         Ok(stylesheet) => stylesheet,
-        Err(error) => return Err(error.into()),
+        Err(error) => {
+            let (line, col) = line_bounds.get_line_col(error.span.start);
+            return Err(Error::Parser(error, line, col));
+        }
     };
 
     Ok(print_stylesheet(

malva/src/line_bounds.rs

@@ -19,23 +19,23 @@ impl LineBounds {
             end >= start,
             "end {end} must be greater than or equal start {start}"
         );
+        self.get_line_at(end) - self.get_line_at(start)
+    }
 
-        let (ControlFlow::Break(start) | ControlFlow::Continue(start)) =
-            self.0
-                .iter()
-                .try_fold(0, |i, offset| match start.cmp(offset) {
-                    Ordering::Less => ControlFlow::Break(i),
-                    Ordering::Equal => ControlFlow::Continue(i),
-                    Ordering::Greater => ControlFlow::Continue(i + 1),
-                });
-        let (ControlFlow::Break(end) | ControlFlow::Continue(end)) =
+    pub(crate) fn get_line_col(&self, pos: usize) -> (usize, usize) {
+        let line = self.get_line_at(pos);
+        (line, pos - self.0[line - 1])
+    }
+
+    fn get_line_at(&self, pos: usize) -> usize {
+        let (ControlFlow::Break(line) | ControlFlow::Continue(line)) =
             self.0
                 .iter()
-                .try_fold(0, |i, offset| match end.cmp(offset) {
+                .try_fold(0, |i, offset| match pos.cmp(offset) {
                     Ordering::Less => ControlFlow::Break(i),
                     Ordering::Equal => ControlFlow::Continue(i),
                     Ordering::Greater => ControlFlow::Continue(i + 1),
                 });
-        end - start
+        line
     }
 }