autolink: identify & permit rem == 0 case.

Author: kivikakk

src/parser/autolink.rs

@@ -123,13 +123,17 @@ pub(crate) fn process_email_autolinks<'a>(
 // - if remaining `i` is equal to the byte count `x`,
 //     set `e = sp.end.column` and finish.
 // - if remaining `i` is less than the byte count `x`,
-//     assert `sp.end.column - sp.start.column + 1 == x` (1),
+//     assert `sp.end.column - sp.start.column + 1 == x || rem == 0` (1),
 //     set `e = sp.start.column + i - 1` and finish.
 //
 // (1) If `x` doesn't equal the range covered between the start and end column,
 //     there's no way to determine sourcepos within the range. This is a bug if
 //     it happens; it suggests we've matched an email autolink with some smart
 //     punctuation in it, or worse.
+//
+//     The one exception is if `rem == 0`. Given nothing to consume, we can
+//     happily restore what we popped, returning `sp.start.column - 1` for the
+//     end column of the original node.
 fn consume_spx(spx: &mut VecDeque<(Sourcepos, usize)>, mut rem: usize) -> usize {
     while let Some((sp, x)) = spx.pop_front() {
         if rem > x {
@@ -138,7 +142,7 @@ fn consume_spx(spx: &mut VecDeque<(Sourcepos, usize)>, mut rem: usize) -> usize
             return sp.end.column;
         } else {
             // rem < x
-            assert_eq!(sp.end.column - sp.start.column + 1, x);
+            assert!((sp.end.column - sp.start.column + 1 == x) || rem == 0);
             spx.push_front((
                 (
                     sp.start.line,

src/tests/fuzz.rs

@@ -276,16 +276,12 @@ fn echaw4() {
 fn echaw5() {
     assert_ast_match!(
         [],
-        // [extension.autolink],
         "_#[email protected]",
         (document (1:1-1:9) [
             (paragraph (1:1-1:9) [
                 (emph (1:1-1:3) [
                     (text (1:2-1:2) "#")
                 ])
-                // (link (1:1-1:14) "mailto:-@_.e" [
-                //     (text (1:1-1:14) "-@_.e")
-                // ])
                 (text (1:4-1:9) "[email protected]")
             ])
         ])
@@ -309,3 +305,18 @@ fn echaw6() {
         ])
     );
 }
+
+#[test]
+fn echaw7() {
+    assert_ast_match!(
+        [extension.autolink],
+        "A[email protected]",
+        (document (1:1-1:10) [
+            (paragraph (1:1-1:10) [
+                (link (1:1-1:10) "mailto:[email protected]" [
+                    (text (1:1-1:10) "[email protected]")
+                ])
+            ])
+        ])
+    );
+}