Use footnote name for reference id

src/cm.rs

@@ -355,9 +355,11 @@ impl<'a, 'o> CommonMarkFormatter<'a, 'o> {
             NodeValue::Table(..) => self.format_table(entering),
             NodeValue::TableRow(..) => self.format_table_row(entering),
             NodeValue::TableCell => self.format_table_cell(node, entering),
-            NodeValue::FootnoteDefinition(_) => self.format_footnote_definition(entering),
-            NodeValue::FootnoteReference(ref r) => {
-                self.format_footnote_reference(r.as_bytes(), entering)
+            NodeValue::FootnoteDefinition(ref nfd) => {
+                self.format_footnote_definition(&nfd.name, entering)
+            }
+            NodeValue::FootnoteReference(ref nfr) => {
+                self.format_footnote_reference(nfr.name.as_bytes(), entering)
             }
         };
         true
@@ -738,11 +740,10 @@ impl<'a, 'o> CommonMarkFormatter<'a, 'o> {
             }
         }
     }
-    fn format_footnote_definition(&mut self, entering: bool) {
+    fn format_footnote_definition(&mut self, name: &str, entering: bool) {
         if entering {
             self.footnote_ix += 1;
-            let footnote_ix = self.footnote_ix;
-            writeln!(self, "[^{}]:", footnote_ix).unwrap();
+            writeln!(self, "[^{}]:", name).unwrap();
             write!(self.prefix, "    ").unwrap();
         } else {
             let new_len = self.prefix.len() - 4;

src/html.rs

@@ -1,6 +1,8 @@
 //! The HTML renderer for the CommonMark AST, as well as helper functions.
 use crate::ctype::isspace;
-use crate::nodes::{AstNode, ListType, NodeCode, NodeValue, TableAlignment};
+use crate::nodes::{
+    AstNode, ListType, NodeCode, NodeFootnoteDefinition, NodeValue, TableAlignment,
+};
 use crate::parser::{ComrakOptions, ComrakPlugins};
 use crate::scanners;
 use once_cell::sync::Lazy;
@@ -701,13 +703,13 @@ impl<'o> HtmlFormatter<'o> {
                         self.render_sourcepos(node)?;
                         self.output.write_all(b">")?;
                     } else {
-                        if matches!(
-                            node.parent().unwrap().data.borrow().value,
-                            NodeValue::FootnoteDefinition(..)
-                        ) && node.next_sibling().is_none()
+                        if let NodeValue::FootnoteDefinition(nfd) =
+                            &node.parent().unwrap().data.borrow().value
                         {
-                            self.output.write_all(b" ")?;
-                            self.put_footnote_backref()?;
+                            if node.next_sibling().is_none() {
+                                self.output.write_all(b" ")?;
+                                self.put_footnote_backref(nfd)?;
+                            }
                         }
                         self.output.write_all(b"</p>\n")?;
                     }
@@ -931,7 +933,7 @@ impl<'o> HtmlFormatter<'o> {
                     self.output.write_all(b"</td>")?;
                 }
             }
-            NodeValue::FootnoteDefinition(_) => {
+            NodeValue::FootnoteDefinition(ref nfd) => {
                 if entering {
                     if self.footnote_ix == 0 {
                         self.output.write_all(b"<section")?;
@@ -942,21 +944,27 @@ impl<'o> HtmlFormatter<'o> {
                     self.footnote_ix += 1;
                     self.output.write_all(b"<li")?;
                     self.render_sourcepos(node)?;
-                    writeln!(self.output, " id=\"fn-{}\">", self.footnote_ix)?;
+                    writeln!(self.output, " id=\"fn-{}\">", nfd.name)?;
                 } else {
-                    if self.put_footnote_backref()? {
+                    if self.put_footnote_backref(nfd)? {
                         self.output.write_all(b"\n")?;
                     }
                     self.output.write_all(b"</li>\n")?;
                 }
             }
-            NodeValue::FootnoteReference(ref r) => {
+            NodeValue::FootnoteReference(ref nfr) => {
                 if entering {
+                    let mut ref_id = format!("fnref-{}", nfr.name);
+
                     self.output.write_all(b"<sup")?;
                     self.render_sourcepos(node)?;
+
+                    if nfr.ref_num > 1 {
+                        ref_id = format!("{}-{}", ref_id, nfr.ref_num);
+                    }
                     write!(
-                        self.output, " class=\"footnote-ref\"><a href=\"#fn-{}\" id=\"fnref-{}\" data-footnote-ref>{}</a></sup>",
-                        r, r, r
+                        self.output, " class=\"footnote-ref\"><a href=\"#fn-{}\" id=\"{}\" data-footnote-ref>{}</a></sup>",
+                        nfr.name, ref_id, nfr.ix,
                     )?;
                 }
             }
@@ -993,17 +1001,29 @@ impl<'o> HtmlFormatter<'o> {
         Ok(())
     }
 
-    fn put_footnote_backref(&mut self) -> io::Result<bool> {
+    fn put_footnote_backref(&mut self, nfd: &NodeFootnoteDefinition) -> io::Result<bool> {
         if self.written_footnote_ix >= self.footnote_ix {
             return Ok(false);
         }
 
         self.written_footnote_ix = self.footnote_ix;
-        write!(
-            self.output,
-            "<a href=\"#fnref-{}\" class=\"footnote-backref\" data-footnote-backref aria-label=\"Back to content\">↩</a>",
-            self.footnote_ix
-        )?;
+
+        let mut ref_suffix = String::new();
+        let mut superscript = String::new();
+
+        for ref_num in 1..=nfd.total_references {
+            if ref_num > 1 {
+                ref_suffix = format!("-{}", ref_num);
+                superscript = format!("<sup class=\"footnote-ref\">{}</sup>", ref_num);
+                write!(self.output, " ")?;
+            }
+
+            write!(
+                self.output,
+                "<a href=\"#fnref-{}{}\" class=\"footnote-backref\" data-footnote-backref data-footnote-backref-idx=\"{}{}\" aria-label=\"Back to reference {}{}\">↩{}</a>",
+                nfd.name, ref_suffix, self.footnote_ix, ref_suffix, self.footnote_ix, ref_suffix, superscript
+            )?;
+        }
         Ok(true)
     }
 }

src/nodes.rs

@@ -88,7 +88,7 @@ pub enum NodeValue {
 
     /// **Block**. A footnote definition.  The `String` is the footnote's name.
     /// Contains other **blocks**.
-    FootnoteDefinition(String),
+    FootnoteDefinition(NodeFootnoteDefinition),
 
     /// **Block**. A [table](https://github.github.com/gfm/#tables-extension-) per the GFM spec.
     /// Contains table rows.
@@ -145,8 +145,8 @@ pub enum NodeValue {
     /// **Inline**.  An [image](https://github.github.com/gfm/#images).
     Image(NodeLink),
 
-    /// **Inline**.  A footnote reference; the `String` is the referent footnote's name.
-    FootnoteReference(String),
+    /// **Inline**.  A footnote reference.
+    FootnoteReference(NodeFootnoteReference),
 
     #[cfg(feature = "shortcodes")]
     /// **Inline**. An Emoji character generated from a shortcode. Enable with feature "shortcodes".
@@ -329,6 +329,29 @@ pub struct NodeHtmlBlock {
     pub literal: String,
 }
 
+/// The metadata of a footnote definition.
+#[derive(Debug, Default, Clone)]
+pub struct NodeFootnoteDefinition {
+    /// The name of the footnote.
+    pub name: String,
+
+    /// Total number of references to this footnote
+    pub total_references: u32,
+}
+
+/// The metadata of a footnote reference.
+#[derive(Debug, Default, Clone)]
+pub struct NodeFootnoteReference {
+    /// The name of the footnote.
+    pub name: String,
+
+    /// The index of reference to the same footnote
+    pub ref_num: u32,
+
+    /// The index of the footnote in the document.
+    pub ix: u32,
+}
+
 impl NodeValue {
     /// Indicates whether this node is a block node or inline node.
     pub fn block(&self) -> bool {
@@ -422,7 +445,7 @@ impl NodeValue {
             NodeValue::FrontMatter(_) => "frontmatter",
             NodeValue::TaskItem { .. } => "taskitem",
             NodeValue::Superscript => "superscript",
-            NodeValue::FootnoteReference(_) => "footnote_reference",
+            NodeValue::FootnoteReference(..) => "footnote_reference",
             #[cfg(feature = "shortcodes")]
             NodeValue::ShortCode(_) => "shortcode",
         }

src/parser/inlines.rs

@@ -1,7 +1,7 @@
 use crate::arena_tree::Node;
 use crate::ctype::{ispunct, isspace};
 use crate::entity;
-use crate::nodes::{Ast, AstNode, NodeCode, NodeLink, NodeValue, Sourcepos};
+use crate::nodes::{Ast, AstNode, NodeCode, NodeFootnoteReference, NodeLink, NodeValue, Sourcepos};
 #[cfg(feature = "shortcodes")]
 use crate::parser::shortcodes::NodeShortCode;
 use crate::parser::{
@@ -1229,7 +1229,11 @@ impl<'a, 'r, 'o, 'd, 'i, 'c, 'subj> Subject<'a, 'r, 'o, 'd, 'i, 'c, 'subj> {
             let text = text.unwrap();
             if text.len() > 1 && text.as_bytes()[0] == b'^' {
                 let inl = self.make_inline(
-                    NodeValue::FootnoteReference(text[1..].to_string()),
+                    NodeValue::FootnoteReference(NodeFootnoteReference {
+                        name: text[1..].to_string(),
+                        ref_num: 0,
+                        ix: 0,
+                    }),
                     // Overridden immediately below.
                     self.pos,
                     self.pos,

src/parser/mod.rs

@@ -8,7 +8,7 @@ use crate::adapters::SyntaxHighlighterAdapter;
 use crate::arena_tree::Node;
 use crate::ctype::{isdigit, isspace};
 use crate::entity;
-use crate::nodes::{self, Sourcepos};
+use crate::nodes::{self, NodeFootnoteDefinition, Sourcepos};
 use crate::nodes::{
     Ast, AstNode, ListDelimType, ListType, NodeCodeBlock, NodeDescriptionItem, NodeHeading,
     NodeHtmlBlock, NodeList, NodeValue,
@@ -256,7 +256,7 @@ pub struct ComrakExtensionOptions {
     /// let mut options = ComrakOptions::default();
     /// options.extension.footnotes = true;
     /// assert_eq!(markdown_to_html("Hi[^x].\n\n[^x]: A greeting.\n", &options),
-    ///            "<p>Hi<sup class=\"footnote-ref\"><a href=\"#fn-1\" id=\"fnref-1\" data-footnote-ref>1</a></sup>.</p>\n<section class=\"footnotes\" data-footnotes>\n<ol>\n<li id=\"fn-1\">\n<p>A greeting. <a href=\"#fnref-1\" class=\"footnote-backref\" data-footnote-backref aria-label=\"Back to content\">↩</a></p>\n</li>\n</ol>\n</section>\n");
+    ///            "<p>Hi<sup class=\"footnote-ref\"><a href=\"#fn-x\" id=\"fnref-x\" data-footnote-ref>1</a></sup>.</p>\n<section class=\"footnotes\" data-footnotes>\n<ol>\n<li id=\"fn-x\">\n<p>A greeting. <a href=\"#fnref-x\" class=\"footnote-backref\" data-footnote-backref data-footnote-backref-idx=\"1\" aria-label=\"Back to reference 1\">↩</a></p>\n</li>\n</ol>\n</section>\n");
     /// ```
     pub footnotes: bool,
 
@@ -600,6 +600,8 @@ pub struct Reference {
 struct FootnoteDefinition<'a> {
     ix: Option<u32>,
     node: &'a AstNode<'a>,
+    name: String,
+    total_references: u32,
 }
 
 impl<'a, 'o, 'c> Parser<'a, 'o, 'c> {
@@ -1080,7 +1082,10 @@ impl<'a, 'o, 'c> Parser<'a, 'o, 'c> {
                 self.advance_offset(line, offset, false);
                 *container = self.add_child(
                     container,
-                    NodeValue::FootnoteDefinition(str::from_utf8(c).unwrap().to_string()),
+                    NodeValue::FootnoteDefinition(NodeFootnoteDefinition {
+                        name: str::from_utf8(c).unwrap().to_string(),
+                        total_references: 0,
+                    }),
                     self.first_nonspace + 1,
                 );
                 container.data.borrow_mut().internal_offset = matched;
@@ -1758,10 +1763,11 @@ impl<'a, 'o, 'c> Parser<'a, 'o, 'c> {
             let mut v = map.into_values().collect::<Vec<_>>();
             v.sort_unstable_by(|a, b| a.ix.cmp(&b.ix));
             for f in v {
-                if let Some(ix) = f.ix {
+                if f.ix.is_some() {
                     match f.node.data.borrow_mut().value {
-                        NodeValue::FootnoteDefinition(ref mut name) => {
-                            *name = format!("{}", ix);
+                        NodeValue::FootnoteDefinition(ref mut nfd) => {
+                            nfd.name = f.name.to_string();
+                            nfd.total_references = f.total_references;
                         }
                         _ => unreachable!(),
                     }
@@ -1776,11 +1782,16 @@ impl<'a, 'o, 'c> Parser<'a, 'o, 'c> {
         map: &mut HashMap<String, FootnoteDefinition<'a>>,
     ) {
         match node.data.borrow().value {
-            NodeValue::FootnoteDefinition(ref name) => {
+            NodeValue::FootnoteDefinition(ref nfd) => {
                 node.detach();
                 map.insert(
-                    strings::normalize_label(name),
-                    FootnoteDefinition { ix: None, node },
+                    strings::normalize_label(&nfd.name),
+                    FootnoteDefinition {
+                        ix: None,
+                        node,
+                        name: strings::normalize_label(&nfd.name),
+                        total_references: 0,
+                    },
                 );
             }
             _ => {
@@ -1799,8 +1810,8 @@ impl<'a, 'o, 'c> Parser<'a, 'o, 'c> {
         let mut ast = node.data.borrow_mut();
         let mut replace = None;
         match ast.value {
-            NodeValue::FootnoteReference(ref mut name) => {
-                if let Some(ref mut footnote) = map.get_mut(name) {
+            NodeValue::FootnoteReference(ref mut nfr) => {
+                if let Some(ref mut footnote) = map.get_mut(&nfr.name) {
                     let ix = match footnote.ix {
                         Some(ix) => ix,
                         None => {
@@ -1809,9 +1820,11 @@ impl<'a, 'o, 'c> Parser<'a, 'o, 'c> {
                             *ixp
                         }
                     };
-                    *name = format!("{}", ix);
+                    footnote.total_references += 1;
+                    nfr.ref_num = footnote.total_references;
+                    nfr.ix = ix;
                 } else {
-                    replace = Some(name.clone());
+                    replace = Some(nfr.name.clone());
                 }
             }
             _ => {

src/tests/api.rs

@@ -164,8 +164,9 @@ fn exercise_full_api() {
             let _: bool = nh.setext;
         }
         nodes::NodeValue::ThematicBreak => {}
-        nodes::NodeValue::FootnoteDefinition(name) => {
-            let _: &String = name;
+        nodes::NodeValue::FootnoteDefinition(nfd) => {
+            let _: &String = &nfd.name;
+            let _: u32 = nfd.total_references;
         }
         nodes::NodeValue::Table(aligns) => {
             let _: &Vec<nodes::TableAlignment> = aligns;
@@ -207,8 +208,9 @@ fn exercise_full_api() {
         nodes::NodeValue::ShortCode(ne) => {
             let _: &str = ne.shortcode();
         }
-        nodes::NodeValue::FootnoteReference(name) => {
-            let _: &String = name;
+        nodes::NodeValue::FootnoteReference(nfr) => {
+            let _: String = nfr.name;
+            let _: u32 = nfr.ix;
         }
     }
 }