wip for #207

src/indentation.rs

@@ -49,13 +49,23 @@
 /// ```
 pub fn indent(s: &str, prefix: &str) -> String {
     let mut result = String::new();
-    for line in s.lines() {
-        if line.chars().any(|c| !c.is_whitespace()) {
+    let mut lines = s.lines().peekable();
+
+    while let Some(line) = lines.next() {
+        if line.chars().next().is_none() {
+            result.push('\n');
+            continue;
+        }
+        let char_count = line.trim_start().chars().count();
+        if char_count != 0 {
             result.push_str(prefix);
             result.push_str(line);
         }
-        result.push('\n');
+        if lines.peek().is_some() {
+            result.push('\n');
+        }
     }
+
     result
 }
 
@@ -141,7 +151,7 @@ mod tests {
     /// Add newlines. Ensures that the final line in the vector also
     /// has a newline.
     fn add_nl(lines: &[&str]) -> String {
-        lines.join("\n") + "\n"
+        lines.join("\n")
     }
 
     #[test]
@@ -152,27 +162,38 @@ mod tests {
     #[test]
     #[rustfmt::skip]
     fn indent_nonempty() {
-        let x = vec!["  foo",
-                     "bar",
-                     "  baz"];
-        let y = vec!["//  foo",
-                     "//bar",
-                     "//  baz"];
-        assert_eq!(indent(&add_nl(&x), "//"), add_nl(&y));
+        let text = r##"  foo
+bar
+  baz"##;
+
+        let expected = r##"//  foo
+//bar
+//  baz"##;
+        assert_eq!(indent(text, "//"), expected);
     }
 
     #[test]
     #[rustfmt::skip]
     fn indent_empty_line() {
-        let x = vec!["  foo",
-                     "bar",
-                     "",
-                     "  baz"];
-        let y = vec!["//  foo",
-                     "//bar",
-                     "",
-                     "//  baz"];
-        assert_eq!(indent(&add_nl(&x), "//"), add_nl(&y));
+        let text = r##"  foo
+bar
+
+  baz"##;
+
+        let expected = r##"//  foo
+//bar
+
+//  baz"##;
+        assert_eq!(indent(text, "//"), expected);
+    }
+
+    #[test]
+    fn indented_text_should_have_the_same_number_of_lines_as_the_original_text() {
+        let texts = ["foo\nbar", "foo\nbar\n", "foo\nbar\nbaz"];
+        for original in texts.iter() {
+            let indented = indent(original, "");
+            assert_eq!(&indented, original);
+        }
     }
 
     #[test]