Regex: Fix handling of ^ and $ in backward matching mode

3 files changed, 19 insertions, 8 deletions

diff --git a/src/regex_impl.cc b/src/regex_impl.cc
index bb1f3537..11d0429a 100644
--- a/src/regex_impl.cc
+++ b/src/regex_impl.cc
@@ -1193,6 +1193,12 @@ auto test_regex = UnitTest{[]{
     }
 
     {
+        TestVM<MatchDirection::Backward> vm{R"($)"};
+        kak_assert(vm.exec("foo\nbar\nbaz\nqux", RegexExecFlags::Search | RegexExecFlags::NotEndOfLine));
+        kak_assert(StringView{vm.captures()[0]}  == "\nqux");
+    }
+
+    {
         TestVM<> vm{R"(()*)"};
         kak_assert(not vm.exec(" "));
     }
diff --git a/src/regex_impl.hh b/src/regex_impl.hh
index 6f2137ce..9a8efdd7 100644
--- a/src/regex_impl.hh
+++ b/src/regex_impl.hh
@@ -130,23 +130,28 @@ public:
 
     bool exec(Iterator begin, Iterator end, RegexExecFlags flags)
     {
-        const bool forward = direction == MatchDirection::Forward;
+        if (flags & RegexExecFlags::NotInitialNull and begin == end)
+            return false;
+
+        constexpr bool forward = direction == MatchDirection::Forward;
         const bool prev_avail = flags & RegexExecFlags::PrevAvailable;
+
         m_begin = Utf8It{utf8::iterator<Iterator>{forward ? begin : end,
                                                   prev_avail ? begin-1 : begin, end}};
         m_end = Utf8It{utf8::iterator<Iterator>{forward ? end : begin,
                                                 prev_avail ? begin-1 : begin, end}};
-        m_flags = flags;
-
-        if (flags & RegexExecFlags::NotInitialNull and m_begin == m_end)
-            return false;
+        if (forward)
+            m_flags = flags;
+        else // Flip line begin/end flags as we flipped the instructions on compilation.
+            m_flags = (RegexExecFlags)(flags & ~(RegexExecFlags::NotEndOfLine | RegexExecFlags::NotBeginOfLine)) |
+                ((flags & RegexExecFlags::NotEndOfLine) ? RegexExecFlags::NotBeginOfLine : RegexExecFlags::None) |
+                ((flags & RegexExecFlags::NotBeginOfLine) ? RegexExecFlags::NotEndOfLine : RegexExecFlags::None);
 
 
-        const bool no_saves = (m_flags & RegexExecFlags::NoSaves);
+        const bool no_saves = (flags & RegexExecFlags::NoSaves);
         Utf8It start{m_begin};
 
         const bool* start_chars = m_program.start_chars ? m_program.start_chars->map : nullptr;
-
         if (flags & RegexExecFlags::Search)
             to_next_start(start, m_end, start_chars);
 
diff --git a/src/selectors.cc b/src/selectors.cc
index c7f237c2..0585c63c 100644
--- a/src/selectors.cc
+++ b/src/selectors.cc
@@ -881,7 +881,7 @@ Selection find_next_match(const Context& context, const Selection& sel, const Re
     wrapped = false;
     const bool found = (direction == MatchDirection::Forward) ?
         find_next(buffer, utf8::next(pos, buffer.end()), matches, regex, wrapped)
-      : find_prev(buffer, pos, matches, regex, wrapped);
+      : find_prev(buffer, utf8::previous(pos, buffer.begin()), matches, regex, wrapped);
 
     if (not found or matches[0].first == buffer.end())
         throw runtime_error(format("'{}': no matches found", regex.str()));