[gtksourceview] implregex: make matching closer to gregex

[Christian Hergert <chergert src gnome org>]

commit c5d6d8590974a517b23b08d62fec2f4a2f5d21f5
Author: Christian Hergert <chergert redhat com>
Date:   Fri Jul 2 12:34:22 2021 -0700

    implregex: make matching closer to gregex

 gtksourceview/implregex.c | 57 +++++++++++++++++++++++++++--------------------
 testsuite/test-regex.c    |  6 +++++
 2 files changed, 39 insertions(+), 24 deletions(-)
---
diff --git a/gtksourceview/implregex.c b/gtksourceview/implregex.c
index 56750106..ed800a06 100644
--- a/gtksourceview/implregex.c
+++ b/gtksourceview/implregex.c
@@ -1012,7 +1012,7 @@ impl_match_info_matches (const ImplMatchInfo *match_info)
        g_return_val_if_fail (match_info != NULL, FALSE);
        g_return_val_if_fail (match_info->n_groups != 0, FALSE);
 
-       return match_info->n_groups > 0;
+       return match_info->n_groups >= 0;
 }
 
 gboolean
@@ -1021,7 +1021,6 @@ impl_match_info_next (ImplMatchInfo  *match_info,
 {
        gssize prev_end;
        gssize prev_begin;
-       int rc;
 
        GTK_SOURCE_PROFILER_BEGIN_MARK;
 
@@ -1043,13 +1042,13 @@ again:
 
        if (match_info->regex->has_jit)
        {
-               rc = pcre2_jit_match (match_info->regex->code,
-                                     (PCRE2_SPTR)match_info->string,
-                                     match_info->string_len,
-                                     match_info->start_pos,
-                                     match_info->match_flags,
-                                     match_info->match_data,
-                                     NULL);
+               match_info->n_groups = pcre2_jit_match (match_info->regex->code,
+                                                       (PCRE2_SPTR)match_info->string,
+                                                       match_info->string_len,
+                                                       match_info->start_pos,
+                                                       match_info->match_flags,
+                                                       match_info->match_data,
+                                                       NULL);
        }
        else
        {
@@ -1058,30 +1057,32 @@ again:
                if (match_info->regex->compile_flags & PCRE2_UTF)
                        match_flags |= PCRE2_NO_UTF_CHECK;
 
-               rc = pcre2_match (match_info->regex->code,
-                                 (PCRE2_SPTR)match_info->string,
-                                 match_info->string_len,
-                                 match_info->start_pos,
-                                 match_flags,
-                                 match_info->match_data,
-                                 NULL);
+               match_info->n_groups = pcre2_match (match_info->regex->code,
+                                                   (PCRE2_SPTR)match_info->string,
+                                                   match_info->string_len,
+                                                   match_info->start_pos,
+                                                   match_flags,
+                                                   match_info->match_data,
+                                                   NULL);
        }
 
-       if (set_regex_error (error, rc))
+       if (set_regex_error (error, match_info->n_groups))
        {
-               match_info->n_groups = -1;
                match_info->start_pos = match_info->string_len + 1;
                return FALSE;
        }
 
+       /* Avoid infinite loops if the pattern is an empty string or
+        * something equivalent.
+        */
        if (prev_end == match_info->offsets[1])
        {
                const char *next = g_utf8_next_char (match_info->string + prev_end);
 
                if (match_info->start_pos > match_info->string_len)
                {
-                       match_info->start_pos = match_info->string_len + 1;
-                       match_info->n_groups = -1;
+                       match_info->start_pos = -1;
+                       match_info->n_groups = PCRE2_ERROR_NOMATCH;
                        return FALSE;
                }
 
@@ -1092,6 +1093,17 @@ again:
                match_info->start_pos = match_info->offsets[1];
        }
 
+       /* it's possible to get two identical matches when we are matching
+        * empty strings, for instance if the pattern is "(?=[A-Z0-9])" and
+        * the string is "RegExTest" we have:
+        *  - search at position 0: match from 0 to 0
+        *  - search at position 1: match from 3 to 3
+        *  - search at position 3: match from 3 to 3 (duplicate)
+        *  - search at position 4: match from 5 to 5
+        *  - search at position 5: match from 5 to 5 (duplicate)
+        *  - search at position 6: no match -> stop
+        * so we have to ignore the duplicates.
+        * see bug #515944: http://bugzilla.gnome.org/show_bug.cgi?id=515944 */
        if (match_info->n_groups >= 0 &&
            prev_begin == match_info->offsets[0] &&
            prev_end == match_info->offsets[1])
@@ -1099,10 +1111,7 @@ again:
                goto again;
        }
 
-       match_info->n_groups = rc;
-
        g_assert (match_info->offsets == pcre2_get_ovector_pointer (match_info->match_data));
-       g_assert (impl_match_info_matches (match_info));
 
        GTK_SOURCE_PROFILER_END_MARK (G_STRFUNC, NULL);
 
@@ -1135,5 +1144,5 @@ impl_match_info_get_match_count (const ImplMatchInfo *match_info)
 {
        g_return_val_if_fail (match_info != NULL, 0);
 
-       return MAX (0, match_info->n_groups);
+       return match_info->n_groups;
 }
diff --git a/testsuite/test-regex.c b/testsuite/test-regex.c
index d2cde8e2..115b38a8 100644
--- a/testsuite/test-regex.c
+++ b/testsuite/test-regex.c
@@ -127,11 +127,17 @@ test_compare (void)
   compare_impl_regex_to_g_regex ("hello\nworld\n", "\\w+", 0);
   compare_impl_regex_to_g_regex ("hello\nworld\n", "\\w+", G_REGEX_OPTIMIZE);
 
+  compare_impl_regex_to_g_regex ("hello\nworld\n", "(.*)*", 0);
+  compare_impl_regex_to_g_regex ("hello\nworld\n", "(.*)*", G_REGEX_OPTIMIZE);
+
   compare_impl_regex_to_g_regex ("aa#bb", "(\\w+)#(\\w+)", 0);
   compare_impl_regex_to_g_regex ("aa#bb", "(\\w+)#(\\w+)", G_REGEX_OPTIMIZE);
 
   compare_impl_regex_to_g_regex ("aa#bb cc#dd", "(\\w+)#(\\w+)", 0);
   compare_impl_regex_to_g_regex ("aa#bb cc#dd", "(\\w+)#(\\w+)", G_REGEX_OPTIMIZE);
+
+  compare_impl_regex_to_g_regex ("hello\nworld\n", "(.*\n)*", 0);
+  compare_impl_regex_to_g_regex ("hello\nworld\n", "(.*\n)*", G_REGEX_OPTIMIZE);
 }
 
 int