Vendor things

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

@@ -0,0 +1,69 @@
+use std::error::Error;
+
+use regex_automata::{
+    dfa::{dense, Automaton, OverlappingState},
+    nfa::thompson,
+    HalfMatch, Input, MatchError,
+};
+
+// Tests that quit bytes in the forward direction work correctly.
+#[test]
+fn quit_fwd() -> Result<(), Box<dyn Error>> {
+    let dfa = dense::Builder::new()
+        .configure(dense::Config::new().quit(b'x', true))
+        .build("[[:word:]]+$")?;
+
+    assert_eq!(
+        Err(MatchError::quit(b'x', 3)),
+        dfa.try_search_fwd(&Input::new(b"abcxyz"))
+    );
+    assert_eq!(
+        dfa.try_search_overlapping_fwd(
+            &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 = dense::Builder::new()
+        .configure(dense::Config::new().quit(b'x', true))
+        .thompson(thompson::Config::new().reverse(true))
+        .build("^[[:word:]]+")?;
+
+    assert_eq!(
+        Err(MatchError::quit(b'x', 3)),
+        dfa.try_search_rev(&Input::new(b"abcxyz"))
+    );
+
+    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() {
+    dense::Config::new().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 = dense::Config::new();
+    for b in 0x80..=0xFF {
+        config = config.quit(b, true);
+    }
+    let dfa = dense::Builder::new().configure(config).build(r"\b")?;
+    let expected = HalfMatch::must(0, 1);
+    assert_eq!(Ok(Some(expected)), dfa.try_search_fwd(&Input::new(b" a")));
+    Ok(())
+}

third-party/vendor/regex-automata/tests/dfa/mod.rs

@@ -0,0 +1,8 @@
+#[cfg(all(feature = "dfa-build", feature = "dfa-search"))]
+mod api;
+#[cfg(feature = "dfa-onepass")]
+mod onepass;
+#[cfg(all(feature = "dfa-build", feature = "dfa-search"))]
+mod regression;
+#[cfg(all(not(miri), feature = "dfa-build", feature = "dfa-search"))]
+mod suite;

third-party/vendor/regex-automata/tests/dfa/onepass/mod.rs

@@ -0,0 +1,2 @@
+#[cfg(not(miri))]
+mod suite;

third-party/vendor/regex-automata/tests/dfa/onepass/suite.rs

@@ -0,0 +1,197 @@
+use {
+    anyhow::Result,
+    regex_automata::{
+        dfa::onepass::{self, DFA},
+        nfa::thompson,
+        util::{iter, syntax},
+    },
+    regex_test::{
+        CompiledRegex, Match, RegexTest, SearchKind, Span, TestResult,
+        TestRunner,
+    },
+};
+
+use crate::{create_input, suite, testify_captures, untestify_kind};
+
+const EXPANSIONS: &[&str] = &["is_match", "find", "captures"];
+
+/// Tests the default configuration of the hybrid NFA/DFA.
+#[test]
+fn default() -> Result<()> {
+    let builder = DFA::builder();
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .test_iter(suite()?.iter(), compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Tests the hybrid NFA/DFA when 'starts_for_each_pattern' is enabled for all
+/// tests.
+#[test]
+fn starts_for_each_pattern() -> Result<()> {
+    let mut builder = DFA::builder();
+    builder.configure(DFA::config().starts_for_each_pattern(true));
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .test_iter(suite()?.iter(), compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Tests the hybrid NFA/DFA when byte classes are disabled.
+///
+/// N.B. Disabling byte classes doesn't avoid any indirection at search time.
+/// All it does is cause every byte value to be its own distinct equivalence
+/// class.
+#[test]
+fn no_byte_classes() -> Result<()> {
+    let mut builder = DFA::builder();
+    builder.configure(DFA::config().byte_classes(false));
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .test_iter(suite()?.iter(), compiler(builder))
+        .assert();
+    Ok(())
+}
+
+fn compiler(
+    mut builder: onepass::Builder,
+) -> impl FnMut(&RegexTest, &[String]) -> Result<CompiledRegex> {
+    move |test, regexes| {
+        // Check if our regex contains things that aren't supported by DFAs.
+        // That is, Unicode word boundaries when searching non-ASCII text.
+        if !configure_onepass_builder(test, &mut builder) {
+            return Ok(CompiledRegex::skip());
+        }
+        let re = match builder.build_many(&regexes) {
+            Ok(re) => re,
+            Err(err) => {
+                let msg = err.to_string();
+                // This is pretty gross, but when a regex fails to compile as
+                // a one-pass regex, then we want to be OK with that and just
+                // skip the test. But we have to be careful to only skip it
+                // when the expected result is that the regex compiles. If
+                // the test is specifically checking that the regex does not
+                // compile, then we should bubble up that error and allow the
+                // test to pass.
+                //
+                // Since our error types are all generally opaque, we just
+                // look for an error string. Not great, but not the end of the
+                // world.
+                if test.compiles() && msg.contains("not one-pass") {
+                    return Ok(CompiledRegex::skip());
+                }
+                return Err(err.into());
+            }
+        };
+        let mut cache = re.create_cache();
+        Ok(CompiledRegex::compiled(move |test| -> TestResult {
+            run_test(&re, &mut cache, test)
+        }))
+    }
+}
+
+fn run_test(
+    re: &DFA,
+    cache: &mut onepass::Cache,
+    test: &RegexTest,
+) -> TestResult {
+    let input = create_input(test);
+    match test.additional_name() {
+        "is_match" => {
+            TestResult::matched(re.is_match(cache, input.earliest(true)))
+        }
+        "find" => match test.search_kind() {
+            SearchKind::Earliest | SearchKind::Leftmost => {
+                let input =
+                    input.earliest(test.search_kind() == SearchKind::Earliest);
+                let mut caps = re.create_captures();
+                let it = iter::Searcher::new(input)
+                    .into_matches_iter(|input| {
+                        re.try_search(cache, input, &mut caps)?;
+                        Ok(caps.get_match())
+                    })
+                    .infallible()
+                    .take(test.match_limit().unwrap_or(std::usize::MAX))
+                    .map(|m| Match {
+                        id: m.pattern().as_usize(),
+                        span: Span { start: m.start(), end: m.end() },
+                    });
+                TestResult::matches(it)
+            }
+            SearchKind::Overlapping => {
+                // The one-pass DFA does not support any kind of overlapping
+                // search. This is not just a matter of not having the API.
+                // It's fundamentally incompatible with the one-pass concept.
+                // If overlapping matches were possible, then the one-pass DFA
+                // would fail to build.
+                TestResult::skip()
+            }
+        },
+        "captures" => match test.search_kind() {
+            SearchKind::Earliest | SearchKind::Leftmost => {
+                let input =
+                    input.earliest(test.search_kind() == SearchKind::Earliest);
+                let it = iter::Searcher::new(input)
+                    .into_captures_iter(re.create_captures(), |input, caps| {
+                        re.try_search(cache, input, caps)
+                    })
+                    .infallible()
+                    .take(test.match_limit().unwrap_or(std::usize::MAX))
+                    .map(|caps| testify_captures(&caps));
+                TestResult::captures(it)
+            }
+            SearchKind::Overlapping => {
+                // The one-pass DFA does not support any kind of overlapping
+                // search. This is not just a matter of not having the API.
+                // It's fundamentally incompatible with the one-pass concept.
+                // If overlapping matches were possible, then the one-pass DFA
+                // would fail to build.
+                TestResult::skip()
+            }
+        },
+        name => TestResult::fail(&format!("unrecognized test name: {}", name)),
+    }
+}
+
+/// Configures the given regex builder with all relevant settings on the given
+/// regex test.
+///
+/// If the regex test has a setting that is unsupported, then this returns
+/// false (implying the test should be skipped).
+fn configure_onepass_builder(
+    test: &RegexTest,
+    builder: &mut onepass::Builder,
+) -> bool {
+    if !test.anchored() {
+        return false;
+    }
+    let match_kind = match untestify_kind(test.match_kind()) {
+        None => return false,
+        Some(k) => k,
+    };
+
+    let config = DFA::config().match_kind(match_kind);
+    builder
+        .configure(config)
+        .syntax(config_syntax(test))
+        .thompson(config_thompson(test));
+    true
+}
+
+/// Configuration of a Thompson NFA compiler from a regex test.
+fn config_thompson(test: &RegexTest) -> thompson::Config {
+    let mut lookm = regex_automata::util::look::LookMatcher::new();
+    lookm.set_line_terminator(test.line_terminator());
+    thompson::Config::new().utf8(test.utf8()).look_matcher(lookm)
+}
+
+/// Configuration of the regex parser from a regex test.
+fn config_syntax(test: &RegexTest) -> syntax::Config {
+    syntax::Config::new()
+        .case_insensitive(test.case_insensitive())
+        .unicode(test.unicode())
+        .utf8(test.utf8())
+        .line_terminator(test.line_terminator())
+}

third-party/vendor/regex-automata/tests/dfa/regression.rs

@@ -0,0 +1,48 @@
+// A regression test for checking that minimization correctly translates
+// whether a state is a match state or not. Previously, it was possible for
+// minimization to mark a non-matching state as matching.
+#[test]
+#[cfg(not(miri))]
+fn minimize_sets_correct_match_states() {
+    use regex_automata::{
+        dfa::{dense::DFA, Automaton, StartKind},
+        Anchored, Input,
+    };
+
+    let pattern =
+        // This is a subset of the grapheme matching regex. I couldn't seem
+        // to get a repro any smaller than this unfortunately.
+        r"(?x)
+            (?:
+                \p{gcb=Prepend}*
+                (?:
+                    (?:
+                        (?:
+                            \p{gcb=L}*
+                            (?:\p{gcb=V}+|\p{gcb=LV}\p{gcb=V}*|\p{gcb=LVT})
+                            \p{gcb=T}*
+                        )
+                        |
+                        \p{gcb=L}+
+                        |
+                        \p{gcb=T}+
+                    )
+                    |
+                    \p{Extended_Pictographic}
+                    (?:\p{gcb=Extend}*\p{gcb=ZWJ}\p{Extended_Pictographic})*
+                    |
+                    [^\p{gcb=Control}\p{gcb=CR}\p{gcb=LF}]
+                )
+                [\p{gcb=Extend}\p{gcb=ZWJ}\p{gcb=SpacingMark}]*
+            )
+        ";
+
+    let dfa = DFA::builder()
+        .configure(
+            DFA::config().start_kind(StartKind::Anchored).minimize(true),
+        )
+        .build(pattern)
+        .unwrap();
+    let input = Input::new(b"\xE2").anchored(Anchored::Yes);
+    assert_eq!(Ok(None), dfa.try_search_fwd(&input));
+}

third-party/vendor/regex-automata/tests/dfa/suite.rs

@@ -0,0 +1,443 @@
+use {
+    anyhow::Result,
+    regex_automata::{
+        dfa::{
+            self, dense, regex::Regex, sparse, Automaton, OverlappingState,
+            StartKind,
+        },
+        nfa::thompson,
+        util::{prefilter::Prefilter, syntax},
+        Anchored, Input, PatternSet,
+    },
+    regex_test::{
+        CompiledRegex, Match, RegexTest, SearchKind, Span, TestResult,
+        TestRunner,
+    },
+};
+
+use crate::{create_input, suite, untestify_kind};
+
+const EXPANSIONS: &[&str] = &["is_match", "find", "which"];
+
+/// Runs the test suite with the default configuration.
+#[test]
+fn unminimized_default() -> Result<()> {
+    let builder = Regex::builder();
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), dense_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Runs the test suite with the default configuration and a prefilter enabled,
+/// if one can be built.
+#[test]
+fn unminimized_prefilter() -> Result<()> {
+    let my_compiler = |test: &RegexTest, regexes: &[String]| {
+        // Parse regexes as HIRs so we can get literals to build a prefilter.
+        let mut hirs = vec![];
+        for pattern in regexes.iter() {
+            hirs.push(syntax::parse_with(pattern, &config_syntax(test))?);
+        }
+        let kind = match untestify_kind(test.match_kind()) {
+            None => return Ok(CompiledRegex::skip()),
+            Some(kind) => kind,
+        };
+        let pre = Prefilter::from_hirs_prefix(kind, &hirs);
+        let mut builder = Regex::builder();
+        builder.dense(dense::DFA::config().prefilter(pre));
+        compiler(builder, |_, _, re| {
+            Ok(CompiledRegex::compiled(move |test| -> TestResult {
+                run_test(&re, test)
+            }))
+        })(test, regexes)
+    };
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), my_compiler)
+        .assert();
+    Ok(())
+}
+
+/// Runs the test suite with start states specialized.
+#[test]
+fn unminimized_specialized_start_states() -> Result<()> {
+    let mut builder = Regex::builder();
+    builder.dense(dense::Config::new().specialize_start_states(true));
+
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), dense_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Runs the test suite with byte classes disabled.
+#[test]
+fn unminimized_no_byte_class() -> Result<()> {
+    let mut builder = Regex::builder();
+    builder.dense(dense::Config::new().byte_classes(false));
+
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), dense_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Runs the test suite with NFA shrinking enabled.
+#[test]
+fn unminimized_nfa_shrink() -> Result<()> {
+    let mut builder = Regex::builder();
+    builder.thompson(thompson::Config::new().shrink(true));
+
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), dense_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Runs the test suite on a minimized DFA with an otherwise default
+/// configuration.
+#[test]
+fn minimized_default() -> Result<()> {
+    let mut builder = Regex::builder();
+    builder.dense(dense::Config::new().minimize(true));
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), dense_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Runs the test suite on a minimized DFA with byte classes disabled.
+#[test]
+fn minimized_no_byte_class() -> Result<()> {
+    let mut builder = Regex::builder();
+    builder.dense(dense::Config::new().minimize(true).byte_classes(false));
+
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), dense_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Runs the test suite on a sparse unminimized DFA.
+#[test]
+fn sparse_unminimized_default() -> Result<()> {
+    let builder = Regex::builder();
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), sparse_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// Runs the test suite on a sparse unminimized DFA with prefilters enabled.
+#[test]
+fn sparse_unminimized_prefilter() -> Result<()> {
+    let my_compiler = |test: &RegexTest, regexes: &[String]| {
+        // Parse regexes as HIRs so we can get literals to build a prefilter.
+        let mut hirs = vec![];
+        for pattern in regexes.iter() {
+            hirs.push(syntax::parse_with(pattern, &config_syntax(test))?);
+        }
+        let kind = match untestify_kind(test.match_kind()) {
+            None => return Ok(CompiledRegex::skip()),
+            Some(kind) => kind,
+        };
+        let pre = Prefilter::from_hirs_prefix(kind, &hirs);
+        let mut builder = Regex::builder();
+        builder.dense(dense::DFA::config().prefilter(pre));
+        compiler(builder, |builder, _, re| {
+            let fwd = re.forward().to_sparse()?;
+            let rev = re.reverse().to_sparse()?;
+            let re = builder.build_from_dfas(fwd, rev);
+            Ok(CompiledRegex::compiled(move |test| -> TestResult {
+                run_test(&re, test)
+            }))
+        })(test, regexes)
+    };
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), my_compiler)
+        .assert();
+    Ok(())
+}
+
+/// Another basic sanity test that checks we can serialize and then deserialize
+/// a regex, and that the resulting regex can be used for searching correctly.
+#[test]
+fn serialization_unminimized_default() -> Result<()> {
+    let builder = Regex::builder();
+    let my_compiler = |builder| {
+        compiler(builder, |builder, _, re| {
+            let builder = builder.clone();
+            let (fwd_bytes, _) = re.forward().to_bytes_native_endian();
+            let (rev_bytes, _) = re.reverse().to_bytes_native_endian();
+            Ok(CompiledRegex::compiled(move |test| -> TestResult {
+                let fwd: dense::DFA<&[u32]> =
+                    dense::DFA::from_bytes(&fwd_bytes).unwrap().0;
+                let rev: dense::DFA<&[u32]> =
+                    dense::DFA::from_bytes(&rev_bytes).unwrap().0;
+                let re = builder.build_from_dfas(fwd, rev);
+
+                run_test(&re, test)
+            }))
+        })
+    };
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), my_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+/// A basic sanity test that checks we can serialize and then deserialize a
+/// regex using sparse DFAs, and that the resulting regex can be used for
+/// searching correctly.
+#[test]
+fn sparse_serialization_unminimized_default() -> Result<()> {
+    let builder = Regex::builder();
+    let my_compiler = |builder| {
+        compiler(builder, |builder, _, re| {
+            let builder = builder.clone();
+            let fwd_bytes = re.forward().to_sparse()?.to_bytes_native_endian();
+            let rev_bytes = re.reverse().to_sparse()?.to_bytes_native_endian();
+            Ok(CompiledRegex::compiled(move |test| -> TestResult {
+                let fwd: sparse::DFA<&[u8]> =
+                    sparse::DFA::from_bytes(&fwd_bytes).unwrap().0;
+                let rev: sparse::DFA<&[u8]> =
+                    sparse::DFA::from_bytes(&rev_bytes).unwrap().0;
+                let re = builder.build_from_dfas(fwd, rev);
+                run_test(&re, test)
+            }))
+        })
+    };
+    TestRunner::new()?
+        .expand(EXPANSIONS, |t| t.compiles())
+        .blacklist("expensive")
+        .test_iter(suite()?.iter(), my_compiler(builder))
+        .assert();
+    Ok(())
+}
+
+fn dense_compiler(
+    builder: dfa::regex::Builder,
+) -> impl FnMut(&RegexTest, &[String]) -> Result<CompiledRegex> {
+    compiler(builder, |_, _, re| {
+        Ok(CompiledRegex::compiled(move |test| -> TestResult {
+            run_test(&re, test)
+        }))
+    })
+}
+
+fn sparse_compiler(
+    builder: dfa::regex::Builder,
+) -> impl FnMut(&RegexTest, &[String]) -> Result<CompiledRegex> {
+    compiler(builder, |builder, _, re| {
+        let fwd = re.forward().to_sparse()?;
+        let rev = re.reverse().to_sparse()?;
+        let re = builder.build_from_dfas(fwd, rev);
+        Ok(CompiledRegex::compiled(move |test| -> TestResult {
+            run_test(&re, test)
+        }))
+    })
+}
+
+fn compiler(
+    mut builder: dfa::regex::Builder,
+    mut create_matcher: impl FnMut(
+        &dfa::regex::Builder,
+        Option<Prefilter>,
+        Regex,
+    ) -> Result<CompiledRegex>,
+) -> impl FnMut(&RegexTest, &[String]) -> Result<CompiledRegex> {
+    move |test, regexes| {
+        // Parse regexes as HIRs for some analysis below.
+        let mut hirs = vec![];
+        for pattern in regexes.iter() {
+            hirs.push(syntax::parse_with(pattern, &config_syntax(test))?);
+        }
+
+        // Get a prefilter in case the test wants it.
+        let kind = match untestify_kind(test.match_kind()) {
+            None => return Ok(CompiledRegex::skip()),
+            Some(kind) => kind,
+        };
+        let pre = Prefilter::from_hirs_prefix(kind, &hirs);
+
+        // Check if our regex contains things that aren't supported by DFAs.
+        // That is, Unicode word boundaries when searching non-ASCII text.
+        if !test.haystack().is_ascii() {
+            for hir in hirs.iter() {
+                if hir.properties().look_set().contains_word_unicode() {
+                    return Ok(CompiledRegex::skip());
+                }
+            }
+        }
+        if !configure_regex_builder(test, &mut builder) {
+            return Ok(CompiledRegex::skip());
+        }
+        create_matcher(&builder, pre, builder.build_many(&regexes)?)
+    }
+}
+
+fn run_test<A: Automaton>(re: &Regex<A>, test: &RegexTest) -> TestResult {
+    let input = create_input(test);
+    match test.additional_name() {
+        "is_match" => TestResult::matched(re.is_match(input.earliest(true))),
+        "find" => match test.search_kind() {
+            SearchKind::Earliest | SearchKind::Leftmost => {
+                let input =
+                    input.earliest(test.search_kind() == SearchKind::Earliest);
+                TestResult::matches(
+                    re.find_iter(input)
+                        .take(test.match_limit().unwrap_or(std::usize::MAX))
+                        .map(|m| Match {
+                            id: m.pattern().as_usize(),
+                            span: Span { start: m.start(), end: m.end() },
+                        }),
+                )
+            }
+            SearchKind::Overlapping => {
+                try_search_overlapping(re, &input).unwrap()
+            }
+        },
+        "which" => match test.search_kind() {
+            SearchKind::Earliest | SearchKind::Leftmost => {
+                // There are no "which" APIs for standard searches.
+                TestResult::skip()
+            }
+            SearchKind::Overlapping => {
+                let dfa = re.forward();
+                let mut patset = PatternSet::new(dfa.pattern_len());
+                dfa.try_which_overlapping_matches(&input, &mut patset)
+                    .unwrap();
+                TestResult::which(patset.iter().map(|p| p.as_usize()))
+            }
+        },
+        name => TestResult::fail(&format!("unrecognized test name: {}", name)),
+    }
+}
+
+/// Configures the given regex builder with all relevant settings on the given
+/// regex test.
+///
+/// If the regex test has a setting that is unsupported, then this returns
+/// false (implying the test should be skipped).
+fn configure_regex_builder(
+    test: &RegexTest,
+    builder: &mut dfa::regex::Builder,
+) -> bool {
+    let match_kind = match untestify_kind(test.match_kind()) {
+        None => return false,
+        Some(k) => k,
+    };
+
+    let starts = if test.anchored() {
+        StartKind::Anchored
+    } else {
+        StartKind::Unanchored
+    };
+    let mut dense_config = dense::Config::new()
+        .start_kind(starts)
+        .match_kind(match_kind)
+        .unicode_word_boundary(true);
+    // When doing an overlapping search, we might try to find the start of each
+    // match with a custom search routine. In that case, we need to tell the
+    // reverse search (for the start offset) which pattern to look for. The
+    // only way that API works is when anchored starting states are compiled
+    // for each pattern. This does technically also enable it for the forward
+    // DFA, but we're okay with that.
+    if test.search_kind() == SearchKind::Overlapping {
+        dense_config = dense_config.starts_for_each_pattern(true);
+    }
+
+    builder
+        .syntax(config_syntax(test))
+        .thompson(config_thompson(test))
+        .dense(dense_config);
+    true
+}
+
+/// Configuration of a Thompson NFA compiler from a regex test.
+fn config_thompson(test: &RegexTest) -> thompson::Config {
+    let mut lookm = regex_automata::util::look::LookMatcher::new();
+    lookm.set_line_terminator(test.line_terminator());
+    thompson::Config::new().utf8(test.utf8()).look_matcher(lookm)
+}
+
+/// Configuration of the regex syntax from a regex test.
+fn config_syntax(test: &RegexTest) -> syntax::Config {
+    syntax::Config::new()
+        .case_insensitive(test.case_insensitive())
+        .unicode(test.unicode())
+        .utf8(test.utf8())
+        .line_terminator(test.line_terminator())
+}
+
+/// Execute an overlapping search, and for each match found, also find its
+/// overlapping starting positions.
+///
+/// N.B. This routine used to be part of the crate API, but 1) it wasn't clear
+/// to me how useful it was and 2) it wasn't clear to me what its semantics
+/// should be. In particular, a potentially surprising footgun of this routine
+/// that it is worst case *quadratic* in the size of the haystack. Namely, it's
+/// possible to report a match at every position, and for every such position,
+/// scan all the way to the beginning of the haystack to find the starting
+/// position. Typical leftmost non-overlapping searches don't suffer from this
+/// because, well, matches can't overlap. So subsequent searches after a match
+/// is found don't revisit previously scanned parts of the haystack.
+///
+/// Its semantics can be strange for other reasons too. For example, given
+/// the regex '.*' and the haystack 'zz', the full set of overlapping matches
+/// is: [0, 0], [1, 1], [0, 1], [2, 2], [1, 2], [0, 2]. The ordering of
+/// those matches is quite strange, but makes sense when you think about the
+/// implementation: an end offset is found left-to-right, and then one or more
+/// starting offsets are found right-to-left.
+///
+/// Nevertheless, we provide this routine in our test suite because it's
+/// useful to test the low level DFA overlapping search and our test suite
+/// is written in a way that requires starting offsets.
+fn try_search_overlapping<A: Automaton>(
+    re: &Regex<A>,
+    input: &Input<'_>,
+) -> Result<TestResult> {
+    let mut matches = vec![];
+    let mut fwd_state = OverlappingState::start();
+    let (fwd_dfa, rev_dfa) = (re.forward(), re.reverse());
+    while let Some(end) = {
+        fwd_dfa.try_search_overlapping_fwd(input, &mut fwd_state)?;
+        fwd_state.get_match()
+    } {
+        let revsearch = input
+            .clone()
+            .range(input.start()..end.offset())
+            .anchored(Anchored::Pattern(end.pattern()))
+            .earliest(false);
+        let mut rev_state = OverlappingState::start();
+        while let Some(start) = {
+            rev_dfa.try_search_overlapping_rev(&revsearch, &mut rev_state)?;
+            rev_state.get_match()
+        } {
+            let span = Span { start: start.offset(), end: end.offset() };
+            let mat = Match { id: end.pattern().as_usize(), span };
+            matches.push(mat);
+        }
+    }
+    Ok(TestResult::matches(matches))
+}