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

src/parser/line_break.rs

@@ -9,6 +9,7 @@ use crate::error::CustomError;
 use crate::error::MyError;
 use crate::error::Res;
 use crate::parser::util::get_consumed;
+use crate::parser::util::get_current_line_before_position;
 use crate::parser::util::get_one_before;
 use crate::parser::LineBreak;
 
@@ -28,7 +29,6 @@ fn pre<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, ()> {
     let preceding_character = get_one_before(document_root, input)
         .map(|slice| slice.chars().next())
         .flatten();
-    // TODO: Must be at the end of a non-empty line so instead of getting one character before, we need to grab the entire line.
     match preceding_character {
         // If None, we are at the start of the file
         None | Some('\\') => {
@@ -38,5 +38,22 @@ fn pre<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, ()> {
         }
         _ => {}
     };
+    let current_line = get_current_line_before_position(document_root, input);
+    match current_line {
+        Some(line) => {
+            let is_non_empty_line = line.chars().any(|c| !c.is_whitespace());
+            if !is_non_empty_line {
+                return Err(nom::Err::Error(CustomError::MyError(MyError(
+                    "Not a valid pre line for line break.",
+                ))));
+            }
+        }
+        None => {
+            return Err(nom::Err::Error(CustomError::MyError(MyError(
+                "No preceding line for line break.",
+            ))));
+        }
+    }
+
     Ok((input, ()))
 }