Fix misnested attention

2 files changed, 29 insertions, 12 deletions

diff --git a/src/construct/attention.rs b/src/construct/attention.rs
index d460afb..d0689b8 100644
--- a/src/construct/attention.rs
+++ b/src/construct/attention.rs
@@ -328,6 +328,25 @@ fn resolve(tokenizer: &mut Tokenizer) -> Vec<Event> {
                         1
                     };
 
+                    // We’re *on* a closing sequence, with a matching opening
+                    // sequence.
+                    // Now we make sure that we can’t have misnested attention:
+                    //
+                    // ```html
+                    // <em>a <strong>b</em> c</strong>
+                    // ```
+                    //
+                    // Do that by marking everything between it as no longer
+                    // possible to open anything.
+                    // Theoretically we could mark non-closing as well, but we
+                    // don’t look for closers backwards.
+                    let mut between = open + 1;
+
+                    while between < close {
+                        sequences[between].open = false;
+                        between += 1;
+                    }
+
                     let sequence_close = &mut sequences[close];
                     let close_event_index = sequence_close.event_index;
                     let seq_close_enter = (
diff --git a/tests/attention.rs b/tests/attention.rs
index 789d860..747bf08 100644
--- a/tests/attention.rs
+++ b/tests/attention.rs
@@ -725,19 +725,17 @@ fn attention() {
     );
 
     // Rule 15.
-    // To do: interleaving attention.
-    // assert_eq!(
-    //     micromark("*foo _bar* baz_"),
-    //     "<p><em>foo _bar</em> baz_</p>",
-    //     "should not support mismatched emphasis"
-    // );
+    assert_eq!(
+        micromark("*foo _bar* baz_"),
+        "<p><em>foo _bar</em> baz_</p>",
+        "should not support mismatched emphasis"
+    );
 
-    // To do: interleaving attention.
-    // assert_eq!(
-    //     micromark("*foo __bar *baz bim__ bam*"),
-    //     "<p><em>foo <strong>bar *baz bim</strong> bam</em></p>",
-    //     "should not support mismatched strong emphasis"
-    // );
+    assert_eq!(
+        micromark("*foo __bar *baz bim__ bam*"),
+        "<p><em>foo <strong>bar *baz bim</strong> bam</em></p>",
+        "should not support mismatched strong emphasis"
+    );
 
     // Rule 16.
     assert_eq!(