vim-patch:8.2.2278: falling back to old regexp engine can some patterns

Problem:    Falling back to old regexp engine can some patterns.
Solution:   Do not fall back once [[:lower:]] or [[:upper:]] is used.
            (Christian Brabandt, closes vim/vim#7572)
66c50c5653

src/nvim/regexp.c

@@ -692,6 +692,7 @@ static char_u *regparse;        ///< Input-scan pointer.
 static int prevchr_len;         ///< byte length of previous char
 static int num_complex_braces;  ///< Complex \{...} count
 static int regnpar;             ///< () count.
+static bool wants_nfa;          ///< regex should use NFA engine
 static int regnzpar;            ///< \z() count.
 static int re_has_z;            ///< \z item detected
 static char_u *regcode;         ///< Code-emit pointer, or JUST_CALC_SIZE
@@ -7248,7 +7249,7 @@ regprog_T *vim_regcomp(char_u *expr_arg, int re_flags)
   // Check for error compiling regexp with initial engine.
   if (prog == NULL) {
 #ifdef BT_REGEXP_DEBUG_LOG
-    // Debugging log for NFA.
+    // Debugging log for BT engine.
     if (regexp_engine != BACKTRACKING_ENGINE) {
       FILE *f = fopen(BT_REGEXP_DEBUG_LOG_NAME, "a");
       if (f) {
@@ -7265,6 +7266,7 @@ regprog_T *vim_regcomp(char_u *expr_arg, int re_flags)
     // But don't try if an error message was given.
     if (regexp_engine == AUTOMATIC_ENGINE && !called_emsg) {
       regexp_engine = BACKTRACKING_ENGINE;
+      report_re_switch(expr);
       prog = bt_regengine.regcomp(expr, re_flags);
     }
   }

src/nvim/regexp_nfa.c

@@ -328,6 +328,11 @@ static int *post_start;   ///< holds the postfix form of r.e.
 static int *post_end;
 static int *post_ptr;
 
+// Set when the pattern should use the NFA engine.
+// E.g. [[:upper:]] only allows 8bit characters for BT engine,
+// while NFA engine handles multibyte characters correctly.
+static bool wants_nfa;
+
 static int nstate;  ///< Number of states in the NFA. Also used when executing.
 static int istate;  ///< Index in the state vector, used in alloc_state()
 
@@ -377,6 +382,7 @@ nfa_regcomp_start (
   post_start = (int *)xmalloc(postfix_size);
   post_ptr = post_start;
   post_end = post_start + nstate_max;
+  wants_nfa = false;
   rex.nfa_has_zend = false;
   rex.nfa_has_backref = false;
 
@@ -1618,6 +1624,7 @@ collection:
               EMIT(NFA_CLASS_GRAPH);
               break;
             case CLASS_LOWER:
+              wants_nfa = true;
               EMIT(NFA_CLASS_LOWER);
               break;
             case CLASS_PRINT:
@@ -1630,6 +1637,7 @@ collection:
               EMIT(NFA_CLASS_SPACE);
               break;
             case CLASS_UPPER:
+              wants_nfa = true;
               EMIT(NFA_CLASS_UPPER);
               break;
             case CLASS_XDIGIT:
@@ -1998,10 +2006,17 @@ static int nfa_regpiece(void)
       return OK;
     }
 
-    // The engine is very inefficient (uses too many states) when the maximum
-    // is much larger than the minimum and when the maximum is large. Bail out
-    // if we can use the other engine.
-    if ((nfa_re_flags & RE_AUTO) && (maxval > 500 || maxval > minval + 200)) {
+    // The engine is very inefficient (uses too many states) when the
+    // maximum is much larger than the minimum and when the maximum is
+    // large.  However, when maxval is MAX_LIMIT, it is okay, as this
+    // will emit NFA_STAR.
+    // Bail out if we can use the other engine, but only, when the
+    // pattern does not need the NFA engine like (e.g. [[:upper:]]\{2,\}
+    // does not work with with characters > 8 bit with the BT engine)
+    if ((nfa_re_flags & RE_AUTO)
+        && (maxval > 500 || maxval > minval + 200)
+        && (maxval != MAX_LIMIT && minval < 200)
+        && !wants_nfa) {
       return FAIL;
     }
 

src/nvim/testdir/test_regexp_utf8.vim

@@ -542,6 +542,52 @@ func Test_match_start_of_line_combining()
   bwipe!
 endfunc
 
+" Check that [[:upper:]] matches for automatic engine
+func Test_match_char_class_upper()
+  new
+  let _engine=&regexpengine
 
+  " Test 1: [[:upper:]]\{2,\}
+  set regexpengine=0
+  call setline(1, ['05. ПЕСНЯ О ГЕРОЯХ муз. А. Давиденко, М. Коваля и Б. Шехтера ...', '05. PJESNJA O GJEROJAKH mus. A. Davidjenko, M. Kovalja i B. Shjekhtjera ...'])
+  call cursor(1,1)
+  let search_cmd='norm /\<[[:upper:]]\{2,\}\>' .. "\<CR>"
+  exe search_cmd
+  call assert_equal(4, searchcount().total, 'TEST 1')
+  set regexpengine=1
+  exe search_cmd
+  call assert_equal(2, searchcount().total, 'TEST 1')
+  set regexpengine=2
+  exe search_cmd
+  call assert_equal(4, searchcount().total, 'TEST 1')
+
+  " Test 2: [[:upper:]].\+
+  let search_cmd='norm /\<[[:upper:]].\+\>' .. "\<CR>"
+  set regexpengine=0
+  exe search_cmd
+  call assert_equal(2, searchcount().total, 'TEST 2')
+  set regexpengine=1
+  exe search_cmd
+  call assert_equal(1, searchcount().total, 'TEST 2')
+  set regexpengine=2
+  exe search_cmd
+  call assert_equal(2, searchcount().total, 'TEST 2')
+
+  " Test 3: [[:lower:]]\+
+  let search_cmd='norm /\<[[:lower:]]\+\>' .. "\<CR>"
+  set regexpengine=0
+  exe search_cmd
+  call assert_equal(4, searchcount().total, 'TEST 3 lower')
+  set regexpengine=1
+  exe search_cmd
+  call assert_equal(2, searchcount().total, 'TEST 3 lower')
+  set regexpengine=2
+  exe search_cmd
+  call assert_equal(4, searchcount().total, 'TEST 3 lower')
+
+  " clean up
+  let &regexpengine=_engine
+  bwipe!
+endfunc
 
 " vim: shiftwidth=2 sts=2 expandtab