From beda08be0a723e8f22491fe7bddbf29ea17efea5 Mon Sep 17 00:00:00 2001
From: Serhiy Barhamon <Bargamon@gmail.com>
Date: Sat, 14 Oct 2023 13:20:43 +0200
Subject: [PATCH] handle multiple fallbacks before non fallback node

---
 src/nodes/yamd.rs           | 16 ++++++++++++++++
 src/toolkit/deserializer.rs | 19 +++++++------------
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/src/nodes/yamd.rs b/src/nodes/yamd.rs
index 54ed751..121ed3d 100644
--- a/src/nodes/yamd.rs
+++ b/src/nodes/yamd.rs
@@ -534,4 +534,20 @@ end"#;
         let actual = Yamd::deserialize(input).unwrap();
         assert_eq!(expected, actual);
     }
+
+    #[test]
+    fn multiple_fallbacks_in_a_row_before_non_fallback() {
+        let input = "1\n\n2\n\n3\n\n# header";
+        let expected = Yamd::new_with_nodes(
+            None,
+            vec![
+                Paragraph::new_with_nodes(false, vec![Text::new("1").into()]).into(),
+                Paragraph::new_with_nodes(false, vec![Text::new("2").into()]).into(),
+                Paragraph::new_with_nodes(false, vec![Text::new("3").into()]).into(),
+                Heading::new(true, "header", 1).into(),
+            ],
+        );
+        let actual = Yamd::deserialize(input).unwrap();
+        assert_eq!(expected, actual);
+    }
 }
diff --git a/src/toolkit/deserializer.rs b/src/toolkit/deserializer.rs
index c13c080..060b38a 100644
--- a/src/toolkit/deserializer.rs
+++ b/src/toolkit/deserializer.rs
@@ -26,8 +26,9 @@ where
             }
             for parser in &maybe_nodes {
                 if let Some(node) = parser(slice, branch.context()) {
-                    if fallback_position != current_position - 1 {
-                        branch.fallback(&input[fallback_position..current_position - 1])?;
+                    while fallback_position != current_position - 1 {
+                        fallback_position =
+                            branch.fallback(&input[fallback_position..current_position - 1])?;
                     }
                     branch.push(node);
                     current_position = branch.len() - branch.get_outer_token_length();
@@ -42,18 +43,12 @@ where
         Some(branch)
     }
 
-    fn fallback(self: &mut Self, slice: &str) -> Option<usize>
+    fn fallback(&mut self, slice: &str) -> Option<usize>
     where
-        Self: Sized + Deserializer + Node,
+        Self: Node,
     {
-        let fallback_node = Self::get_fallback_node();
-        match fallback_node.as_ref() {
-            Some(fallback_node) => {
-                self.push(fallback_node(slice));
-                Some(self.len() - self.get_outer_token_length())
-            }
-            None => return None,
-        }
+        self.push(Self::get_fallback_node().map(|f| f(slice))?);
+        Some(self.len() - self.get_outer_token_length())
     }
 }