to_markdown: fix crash on non-ascii around phrasing

Closes GH-169.
Closes GH-170.

Co-authored-by: bnchi <[email protected]>

Author: wooorm

mdast_util_to_markdown/src/state.rs

@@ -242,7 +242,7 @@ impl<'a> State<'a> {
                     results.push(' ');
                     new_info.before = " ";
                 } else {
-                    new_info.before = &results[results.len() - 1..];
+                    new_info.before = &results;
                 }
             }
 

mdast_util_to_markdown/tests/emphasis.rs

@@ -1,4 +1,4 @@
-use markdown::mdast::{Emphasis, Node, Text};
+use markdown::mdast::{Emphasis, Node, Paragraph, Text};
 use mdast_util_to_markdown::{
     to_markdown as to, to_markdown_with_options as to_md_with_opts, Options,
 };
@@ -47,4 +47,48 @@ fn emphasis() {
         "_a_\n",
         "should support an emphasis w/ underscores when `emphasis: \"_\"`"
     );
+
+    assert_eq!(
+        to(&Node::Paragraph(Paragraph {
+            children: vec![
+                Node::Text(Text {
+                    value: String::from("𝄞"),
+                    position: None
+                }),
+                Node::Emphasis(Emphasis {
+                    children: vec![Node::Text(Text {
+                        value: String::from("a"),
+                        position: None,
+                    })],
+                    position: None
+                })
+            ],
+            position: None
+        }))
+        .unwrap(),
+        "𝄞*a*\n",
+        "should support non-ascii before emphasis"
+    );
+
+    assert_eq!(
+        to(&Node::Paragraph(Paragraph {
+            children: vec![
+                Node::Emphasis(Emphasis {
+                    children: vec![Node::Text(Text {
+                        value: String::from("a"),
+                        position: None,
+                    })],
+                    position: None
+                }),
+                Node::Text(Text {
+                    value: String::from("𝄞"),
+                    position: None
+                }),
+            ],
+            position: None
+        }))
+        .unwrap(),
+        "*a*𝄞\n",
+        "should support non-ascii after emphasis"
+    );
 }