chore: checkpoint before Python removal

vendor/regex-automata/tests/dfa/onepass/regression.rs

@@ -0,0 +1,61 @@
+// Regression test for zero-repetition capture groups,
+// which caused a panic when the Vec passed into search_slots
+// contained space for the capture group which would never
+// have any results.
+//
+// See: https://github.com/rust-lang/regex/issues/1327
+#[test]
+fn zero_repetition_capture_group() {
+    use regex_automata::{
+        dfa::onepass::DFA, util::primitives::NonMaxUsize, Anchored, Input,
+    };
+
+    let expr = DFA::new(r"(abc)(ABC){0}").unwrap();
+    let s = "abcABC";
+    let input = Input::new(s).span(0..s.len()).anchored(Anchored::Yes);
+
+    // Test with 4 slots, so the whole match plus the first capture group.
+    let mut cache = expr.create_cache();
+    let mut slots: Vec<Option<NonMaxUsize>> = vec![None; 4];
+    let pid = expr.try_search_slots(&mut cache, &input, &mut slots).unwrap();
+    assert_eq!(pid, Some(regex_automata::PatternID::must(0)));
+    assert_eq!(slots[0], Some(NonMaxUsize::new(0).unwrap()));
+    assert_eq!(slots[1], Some(NonMaxUsize::new(3).unwrap()));
+    assert_eq!(slots[2], Some(NonMaxUsize::new(0).unwrap()));
+    assert_eq!(slots[3], Some(NonMaxUsize::new(3).unwrap()));
+
+    // Test with larger slot array, which would fit the
+    // zero-repetition capture group.
+    slots.resize(6, None);
+    let pid = expr.try_search_slots(&mut cache, &input, &mut slots).unwrap();
+    assert_eq!(pid, Some(regex_automata::PatternID::must(0)));
+    // First capture group should match
+    assert_eq!(slots[2], Some(NonMaxUsize::new(0).unwrap()));
+    assert_eq!(slots[3], Some(NonMaxUsize::new(3).unwrap()));
+    // Second capture group with {0} should be None.
+    assert_eq!(slots[4], None);
+    assert_eq!(slots[5], None);
+}
+
+// Another regression test for the same case as
+// `zero_repetition_capture_group`, but uses a simpler pattern. That
+// is, a zero-repetition capture group is a red herring. The actual bug
+// is simpler: it happens whenever too many slots are provided by the
+// caller.
+#[test]
+fn too_many_slots_normal_pattern() {
+    use regex_automata::{
+        dfa::onepass::DFA, util::primitives::NonMaxUsize, Anchored, Input,
+    };
+
+    let expr = DFA::new(r"abc").unwrap();
+    let s = "abc";
+    let input = Input::new(s).span(0..s.len()).anchored(Anchored::Yes);
+
+    let mut cache = expr.create_cache();
+    let mut slots: Vec<Option<NonMaxUsize>> = vec![None; 4];
+    let pid = expr.try_search_slots(&mut cache, &input, &mut slots).unwrap();
+    assert_eq!(pid, Some(regex_automata::PatternID::must(0)));
+    assert_eq!(slots[0], Some(NonMaxUsize::new(0).unwrap()));
+    assert_eq!(slots[1], Some(NonMaxUsize::new(3).unwrap()));
+}