update

src/app.rs

@@ -282,7 +282,7 @@ impl App {
             term_width: Term::stdout().size().1 as usize,
             files,
             theme: self.matches.value_of("theme"),
-            line_range: self.matches.value_of("line-range").map(LineRange::from),
+            line_range: transpose(self.matches.value_of("line-range").map(LineRange::from))?,
         })
     }
 
@@ -351,12 +351,12 @@ pub struct LineRange {
 }
 
 impl LineRange {
-    pub fn from(range_raw: &str) -> LineRange {
-        LineRange::parse_range(range_raw).unwrap_or(LineRange::new())
+    pub fn from(range_raw: &str) -> Result<LineRange> {
+        LineRange::parse_range(range_raw)
     }
 
     pub fn new() -> LineRange {
-        LineRange{
+        LineRange {
             lower: usize::min_value(),
             upper: usize::max_value(),
         }
@@ -365,10 +365,10 @@ impl LineRange {
     pub fn parse_range(range_raw: &str) -> Result<LineRange> {
         let mut new_range = LineRange::new();
 
-        if range_raw.bytes().nth(0).ok_or("No first byte")? == b':' {
+        if range_raw.bytes().nth(0).ok_or("Empty line range")? == b':' {
             new_range.upper = range_raw[1..].parse()?;
             return Ok(new_range);
-        } else if range_raw.bytes().last().ok_or("No last byte")? == b':' {
+        } else if range_raw.bytes().last().ok_or("Empty line range")? == b':' {
             new_range.lower = range_raw[..range_raw.len() - 1].parse()?;
             return Ok(new_range);
         }
@@ -377,28 +377,45 @@ impl LineRange {
         if line_numbers.len() == 2 {
             new_range.lower = line_numbers[0].parse()?;
             new_range.upper = line_numbers[1].parse()?;
+            return Ok(new_range);
         }
-        Ok(new_range)                
+        Err("expected single ':' character".into())
     }
 }
 
 #[test]
 fn test_parse_line_range_full() {
-    let range = LineRange::from(Some("40:50")).expect("Shouldn't fail on test!");
+    let range = LineRange::from("40:50").expect("Shouldn't fail on test!");
     assert_eq!(40, range.lower);
     assert_eq!(50, range.upper);
 }
 
 #[test]
 fn test_parse_line_range_partial_min() {
-    let range = LineRange::from(Some(":50")).expect("Shouldn't fail on test!");
+    let range = LineRange::from(":50").expect("Shouldn't fail on test!");
     assert_eq!(usize::min_value(), range.lower);
     assert_eq!(50, range.upper);
 }
 
 #[test]
 fn test_parse_line_range_partial_max() {
-    let range = LineRange::from(Some("40:")).expect("Shouldn't fail on test!");
+    let range = LineRange::from("40:").expect("Shouldn't fail on test!");
     assert_eq!(40, range.lower);
     assert_eq!(usize::max_value(), range.upper);
 }
+
+#[test]
+fn test_parse_line_range_fail() {
+    let range = LineRange::from("40:50:80");
+    assert!(range.is_err());
+    let range = LineRange::from("40::80");
+    assert!(range.is_err());
+    let range = LineRange::from(":40:");
+    assert!(range.is_err());
+    let range = LineRange::from("40");
+    assert!(range.is_err());
+}
+
+fn transpose<T>(opt: Option<Result<T>>) -> Result<Option<T>> {
+    opt.map_or(Ok(None), |res| res.map(Some))
+}