fix: harden again manufactured input which could previously trigger a…

…ssertion failures. (#91)
Byron · Dec 11, 2024 · a368f0f · a368f0f
1 parent b526d7c
commit a368f0f
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Showing 2 changed files with 60 additions and 25 deletions.
diff --git a/src/lib.rs b/src/lib.rs
@@ -470,7 +470,6 @@ where
                     classes,
                     attrs,
                 } => {
-                    assert_eq!(state.current_heading, None);
                     state.current_heading = Some(self::Heading {
                         id: id.as_ref().map(|id| id.clone().into()),
                         classes: classes.iter().map(|class| class.clone().into()).collect(),
@@ -554,34 +553,40 @@ where
             }
         }
         End(tag) => match tag {
-            TagEnd::Link => match state.link_stack.pop().unwrap() {
-                LinkCategory::AngleBracketed => formatter.write_char('>'),
-                LinkCategory::Reference { uri, title, id } => {
-                    state
-                        .shortcuts
-                        .push((id.to_string(), uri.to_string(), title.to_string()));
-                    formatter.write_str("][")?;
-                    formatter.write_str(&id)?;
-                    formatter.write_char(']')
-                }
-                LinkCategory::Collapsed { uri, title } => {
-                    if let Some(shortcut_text) = state.current_shortcut_text.take() {
+            TagEnd::Link => {
+                let Some(category) = state.link_stack.pop() else {
+                    // This should always be present, but people can provide any kind of event stream.
+                    return Ok(());
+                };
+                match category {
+                    LinkCategory::AngleBracketed => formatter.write_char('>'),
+                    LinkCategory::Reference { uri, title, id } => {
                         state
                             .shortcuts
-                            .push((shortcut_text, uri.to_string(), title.to_string()));
+                            .push((id.to_string(), uri.to_string(), title.to_string()));
+                        formatter.write_str("][")?;
+                        formatter.write_str(&id)?;
+                        formatter.write_char(']')
                     }
-                    formatter.write_str("][]")
-                }
-                LinkCategory::Shortcut { uri, title } => {
-                    if let Some(shortcut_text) = state.current_shortcut_text.take() {
-                        state
-                            .shortcuts
-                            .push((shortcut_text, uri.to_string(), title.to_string()));
+                    LinkCategory::Collapsed { uri, title } => {
+                        if let Some(shortcut_text) = state.current_shortcut_text.take() {
+                            state
+                                .shortcuts
+                                .push((shortcut_text, uri.to_string(), title.to_string()));
+                        }
+                        formatter.write_str("][]")
                     }
-                    formatter.write_char(']')
+                    LinkCategory::Shortcut { uri, title } => {
+                        if let Some(shortcut_text) = state.current_shortcut_text.take() {
+                            state
+                                .shortcuts
+                                .push((shortcut_text, uri.to_string(), title.to_string()));
+                        }
+                        formatter.write_char(']')
+                    }
+                    LinkCategory::Other { uri, title } => close_link(&uri, &title, formatter, LinkType::Inline),
                 }
-                LinkCategory::Other { uri, title } => close_link(&uri, &title, formatter, LinkType::Inline),
-            },
+            }
             TagEnd::Image => match state.image_stack.pop().unwrap() {
                 ImageLink::Reference { uri, title, id } => {
                     state
@@ -614,11 +619,15 @@ where
             TagEnd::Emphasis => formatter.write_char(options.emphasis_token),
             TagEnd::Strong => formatter.write_str(options.strong_token),
             TagEnd::Heading(_) => {
+                let Some(heading) = state.current_heading.take() else {
+                    // Harden against manufactured input.
+                    return Ok(());
+                };
                 let self::Heading {
                     id,
                     classes,
                     attributes,
-                } = state.current_heading.take().unwrap();
+                } = heading;
                 let emit_braces = id.is_some() || !classes.is_empty() || !attributes.is_empty();
                 if emit_braces {
                     formatter.write_str(" {")?;

diff --git a/tests/integrate/main.rs b/tests/integrate/main.rs
@@ -1,6 +1,32 @@
 mod display;
 mod fmt;
 mod spec;
+mod fuzzed {
+    use pulldown_cmark::{Event, HeadingLevel, Tag, TagEnd};
+    use pulldown_cmark_to_cmark::cmark_resume;
+
+    #[test]
+    fn cmark_resume_with_options_does_not_panic() {
+        let events = [
+            Event::Start(Tag::Heading {
+                level: HeadingLevel::H2,
+                id: None,
+                classes: vec![],
+                attrs: vec![],
+            }),
+            Event::Start(Tag::Heading {
+                level: HeadingLevel::H2,
+                id: None,
+                classes: vec![],
+                attrs: vec![],
+            }),
+            Event::Text(pulldown_cmark::CowStr::Borrowed("(")),
+            Event::End(TagEnd::Heading(HeadingLevel::H2)),
+            Event::End(TagEnd::Heading(HeadingLevel::H2)),
+        ];
+        let _ = cmark_resume(events.iter(), String::new(), None);
+    }
+}
 
 #[cfg(test)]
 mod calculate_code_block_token_count {