Check that the preceding line for a line break is non-empty.

src/parser/util.rs

@@ -59,6 +59,32 @@ pub fn get_one_before<'s>(document: &'s str, current_position: &'s str) -> Optio
     Some(&document[previous_character_offset..offset])
 }
 
+/// Get the line current_position is on up until current_position
+pub fn get_current_line_before_position<'s>(
+    document: &'s str,
+    current_position: &'s str,
+) -> Option<&'s str> {
+    assert!(is_slice_of(document, current_position));
+    if document.as_ptr() as usize == current_position.as_ptr() as usize {
+        return None;
+    }
+    let offset = current_position.as_ptr() as usize - document.as_ptr() as usize;
+    let mut previous_character_offset = offset;
+    loop {
+        let new_offset = document.floor_char_boundary(previous_character_offset - 1);
+        let new_line = &document[new_offset..offset];
+        let leading_char = new_line
+            .chars()
+            .next()
+            .expect("Impossible to not have at least 1 character to read.");
+        if "\r\n".contains(leading_char) || new_offset == 0 {
+            break;
+        }
+        previous_character_offset = new_offset;
+    }
+    Some(&document[previous_character_offset..offset])
+}
+
 /// Check if the child string slice is a slice of the parent string slice.
 fn is_slice_of(parent: &str, child: &str) -> bool {
     let parent_start = parent.as_ptr() as usize;