Vendor things

third-party/vendor/regex-automata/tests/hybrid/api.rs

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+use std::error::Error;
+
+use regex_automata::{
+    hybrid::dfa::{OverlappingState, DFA},
+    nfa::thompson,
+    HalfMatch, Input, MatchError,
+};
+
+// Tests that too many cache resets cause the lazy DFA to quit.
+//
+// We only test this on 64-bit because the test is gingerly crafted based on
+// implementation details of cache sizes. It's not a great test because of
+// that, but it does check some interesting properties around how positions are
+// reported when a search "gives up."
+//
+// NOTE: If you change something in lazy DFA implementation that causes this
+// test to fail by reporting different "gave up" positions, then it's generally
+// okay to update the positions in the test below as long as you're sure your
+// changes are correct. Namely, it is expected that if there are changes in the
+// cache size (or changes in how big things are inside the cache), then its
+// utilization may change slightly and thus impact where a search gives up.
+// Precisely where a search gives up is not an API guarantee, so changing the
+// offsets here is OK.
+#[test]
+#[cfg(target_pointer_width = "64")]
+#[cfg(not(miri))]
+fn too_many_cache_resets_cause_quit() -> Result<(), Box<dyn Error>> {
+    // This is a carefully chosen regex. The idea is to pick one that requires
+    // some decent number of states (hence the bounded repetition). But we
+    // specifically choose to create a class with an ASCII letter and a
+    // non-ASCII letter so that we can check that no new states are created
+    // once the cache is full. Namely, if we fill up the cache on a haystack
+    // of 'a's, then in order to match one 'β', a new state will need to be
+    // created since a 'β' is encoded with multiple bytes.
+    //
+    // So we proceed by "filling" up the cache by searching a haystack of just
+    // 'a's. The cache won't have enough room to add enough states to find the
+    // match (because of the bounded repetition), which should result in it
+    // giving up before it finds a match.
+    //
+    // Since there's now no more room to create states, we search a haystack
+    // of 'β' and confirm that it gives up immediately.
+    let pattern = r"[aβ]{99}";
+    let dfa = DFA::builder()
+        .configure(
+            // Configure it so that we have the minimum cache capacity
+            // possible. And that if any resets occur, the search quits.
+            DFA::config()
+                .skip_cache_capacity_check(true)
+                .cache_capacity(0)
+                .minimum_cache_clear_count(Some(0)),
+        )
+        .thompson(thompson::NFA::config())
+        .build(pattern)?;
+    let mut cache = dfa.create_cache();
+
+    let haystack = "a".repeat(101).into_bytes();
+    let err = MatchError::gave_up(24);
+    // Notice that we make the same amount of progress in each search! That's
+    // because the cache is reused and already has states to handle the first
+    // N bytes.
+    assert_eq!(
+        Err(err.clone()),
+        dfa.try_search_fwd(&mut cache, &Input::new(&haystack))
+    );
+    assert_eq!(
+        Err(err.clone()),
+        dfa.try_search_overlapping_fwd(
+            &mut cache,
+            &Input::new(&haystack),
+            &mut OverlappingState::start()
+        ),
+    );
+
+    let haystack = "β".repeat(101).into_bytes();
+    let err = MatchError::gave_up(2);
+    assert_eq!(
+        Err(err),
+        dfa.try_search_fwd(&mut cache, &Input::new(&haystack))
+    );
+    // no need to test that other find routines quit, since we did that above
+
+    // OK, if we reset the cache, then we should be able to create more states
+    // and make more progress with searching for betas.
+    cache.reset(&dfa);
+    let err = MatchError::gave_up(26);
+    assert_eq!(
+        Err(err),
+        dfa.try_search_fwd(&mut cache, &Input::new(&haystack))
+    );
+
+    // ... switching back to ASCII still makes progress since it just needs to
+    // set transitions on existing states!
+    let haystack = "a".repeat(101).into_bytes();
+    let err = MatchError::gave_up(13);
+    assert_eq!(
+        Err(err),
+        dfa.try_search_fwd(&mut cache, &Input::new(&haystack))
+    );
+
+    Ok(())
+}
+
+// Tests that quit bytes in the forward direction work correctly.
+#[test]
+fn quit_fwd() -> Result<(), Box<dyn Error>> {
+    let dfa = DFA::builder()
+        .configure(DFA::config().quit(b'x', true))
+        .build("[[:word:]]+$")?;
+    let mut cache = dfa.create_cache();
+
+    assert_eq!(
+        dfa.try_search_fwd(&mut cache, &Input::new("abcxyz")),
+        Err(MatchError::quit(b'x', 3)),
+    );
+    assert_eq!(
+        dfa.try_search_overlapping_fwd(
+            &mut cache,
+            &Input::new(b"abcxyz"),
+            &mut OverlappingState::start()
+        ),
+        Err(MatchError::quit(b'x', 3)),
+    );
+
+    Ok(())
+}
+
+// Tests that quit bytes in the reverse direction work correctly.
+#[test]
+fn quit_rev() -> Result<(), Box<dyn Error>> {
+    let dfa = DFA::builder()
+        .configure(DFA::config().quit(b'x', true))
+        .thompson(thompson::Config::new().reverse(true))
+        .build("^[[:word:]]+")?;
+    let mut cache = dfa.create_cache();
+
+    assert_eq!(
+        dfa.try_search_rev(&mut cache, &Input::new("abcxyz")),
+        Err(MatchError::quit(b'x', 3)),
+    );
+
+    Ok(())
+}
+
+// Tests that if we heuristically enable Unicode word boundaries but then
+// instruct that a non-ASCII byte should NOT be a quit byte, then the builder
+// will panic.
+#[test]
+#[should_panic]
+fn quit_panics() {
+    DFA::config().unicode_word_boundary(true).quit(b'\xFF', false);
+}
+
+// This tests an intesting case where even if the Unicode word boundary option
+// is disabled, setting all non-ASCII bytes to be quit bytes will cause Unicode
+// word boundaries to be enabled.
+#[test]
+fn unicode_word_implicitly_works() -> Result<(), Box<dyn Error>> {
+    let mut config = DFA::config();
+    for b in 0x80..=0xFF {
+        config = config.quit(b, true);
+    }
+    let dfa = DFA::builder().configure(config).build(r"\b")?;
+    let mut cache = dfa.create_cache();
+    let expected = HalfMatch::must(0, 1);
+    assert_eq!(
+        Ok(Some(expected)),
+        dfa.try_search_fwd(&mut cache, &Input::new(" a")),
+    );
+    Ok(())
+}