Fix underflow panics when using TextPrinter::push_span_nobreak (#322)

src/message/printer.rs

@@ -94,7 +94,7 @@ impl<'a> TextPrinter<'a> {
     }
 
     fn remaining(&self) -> usize {
-        self.width - self.curr_width
+        self.width.saturating_sub(self.curr_width)
     }
 
     /// If there is any text on the current line, start a new one.
@@ -276,3 +276,18 @@ impl<'a> TextPrinter<'a> {
         self.text
     }
 }
+
+#[cfg(test)]
+pub mod tests {
+    use super::*;
+
+    #[test]
+    fn test_push_nobreak() {
+        let mut printer = TextPrinter::new(5, Style::default(), false, false);
+        printer.push_span_nobreak("hello world".into());
+        let text = printer.finish();
+        assert_eq!(text.lines.len(), 1);
+        assert_eq!(text.lines[0].spans.len(), 1);
+        assert_eq!(text.lines[0].spans[0].content, "hello world");
+    }
+}