grep: -P (--perl-regexp) \D once again works like [^0-9]

* NEWS: Mention \D, too.
* doc/grep.texi: Likewise
* src/pcresearch.c (pcre_pattern_expand_backslash_d): Handle \D.
Also, ifdef-out this new function and its call site when not needed.
* tests/pcre-ascii-digits: Test \D, too.
Tighten one test by using returns_ 1.
Add comments and tests that work only with 10.43 and newer.
Paul Eggert raised the issue of \D in https://bugs.gnu.org/62267#8

NEWS

@@ -9,7 +9,7 @@ GNU grep NEWS                                    -*- outline -*-
   properly had the undesirable side effect of making \d also match
   e.g., the Arabic digits: ٠١٢٣٤٥٦٧٨٩.  With grep-3.9, -P '\d+'
   would match that ten-digit (20-byte) string. Now, to match such
-  a digit, you would use \p{Nd}.
+  a digit, you would use \p{Nd}. Similarly, \D is now mapped to [^0-9].
   [bug introduced in grep 3.9]
 
 

doc/grep.texi

@@ -1144,21 +1144,15 @@ combined with the @option{-z} (@option{--null-data}) option, and note that
 For documentation, refer to @url{https://www.pcre.org/}, with these caveats:
 @itemize
 @item
-@samp{\d} matches only the ten ASCII digits, regardless of locale.
+@samp{\d} matches only the ten ASCII digits
+(and @samp{\D} matches the complement), regardless of locale.
 Use @samp{\p@{Nd@}} to also match non-ASCII digits.
 
-When @command{grep} is built with PCRE2 10.42 and earlier, @samp{\d}
-ignores in-regexp directives like @samp{(?aD)} and matches only ASCII
-digits regardless of these directives.  However, later versions of
-PCRE2 likely will fix this, and the plan is for @command{grep} to
-respect those directives if possible.
-@c Using PCRE2 git commit pcre2-10.40-112-g6277357, this demonstrates
-@c the equivalent of how grep could use PCRE2_EXTRA_ASCII_BSD to make \d's
-@c ASCII-only behavior the default:
-@c $ LC_ALL=en_US.UTF-8 ./pcre2grep -u '(?aD)^\d+' <<< '٠١٢٣٤٥٦٧٨٩'
-@c [Exit 1]
-@c $ LC_ALL=en_US.UTF-8 ./pcre2grep -u '^\d+' <<< '٠١٢٣٤٥٦٧٨٩'
-@c ٠١٢٣٤٥٦٧٨٩
+When @command{grep} is built with PCRE2 10.42 and earlier,
+@samp{\d} and @samp{\D} ignore in-regexp directives like @samp{(?aD)}
+and work like @samp{[0-9]} and @samp{[^0-9]} respectively.
+However, later versions of PCRE2 likely will fix this,
+and the plan is for @command{grep} to respect those directives if possible.
 
 @item
 Although PCRE tracks the syntax and semantics of Perl's regular

src/pcresearch.c

@@ -133,10 +133,13 @@ bad_utf8_from_pcre2 (int e)
 #endif
 }
 
+#if ! PCRE2_EXTRA_ASCII_BSD
 /* Replace each \d in *KEYS_P with [0-9], to ensure that \d matches only ASCII
    digits.  Now that we enable PCRE2_UCP for pcre regexps, \d would otherwise
    match non-ASCII digits in some locales.  Use \p{Nd} if you require to match
-   those.  */
+   those.  Similarly, replace each \D with [^0-9].
+   FIXME: remove in 2025, or whenever we no longer accommodate pcre2-10.42
+   and prior.  */
 static void
 pcre_pattern_expand_backslash_d (char **keys_p, idx_t *len_p)
 {
@@ -182,6 +185,9 @@ pcre_pattern_expand_backslash_d (char **keys_p, idx_t *len_p)
                 case 'd':
                   p = mempcpy (p, "[0-9]", 5);
                   break;
+                case 'D':
+                  p = mempcpy (p, "[^0-9]", 6);
+                  break;
                 default:
                   *p++ = '\\';
                   *p++ = *keys;
@@ -206,6 +212,7 @@ pcre_pattern_expand_backslash_d (char **keys_p, idx_t *len_p)
   *keys_p = new_keys;
   *len_p = p - new_keys;
 }
+#endif
 
 /* Compile the -P style PATTERN, containing SIZE bytes that are
    followed by '\n'.  Return a description of the compiled pattern.  */
@@ -213,8 +220,9 @@ pcre_pattern_expand_backslash_d (char **keys_p, idx_t *len_p)
 void *
 Pcompile (char *pattern, idx_t size, reg_syntax_t ignored, bool exact)
 {
-  if (! PCRE2_EXTRA_ASCII_BSD)
-    pcre_pattern_expand_backslash_d (&pattern, &size);
+#if ! PCRE2_EXTRA_ASCII_BSD
+  pcre_pattern_expand_backslash_d (&pattern, &size);
+#endif
 
   PCRE2_SIZE e;
   int ec;

tests/pcre-ascii-digits

@@ -1,6 +1,7 @@
 #!/bin/sh
 # Ensure that grep -P's \d matches only the 10 ASCII digits.
 # With, grep-3.9, \d would match e.g., the multibyte Arabic digits.
+# The same applied to \D.
 #
 # Copyright (C) 2023 Free Software Foundation, Inc.
 #
@@ -24,8 +25,38 @@ fail=0
 # \331\245\331\246\331\247\331\250\331\251
 printf '\331\240\331\241\331\242\331\243\331\244' > in || framework_failure_
 printf '\331\245\331\246\331\247\331\250\331\251' >> in || framework_failure_
+printf '\n' >> in || framework_failure_
 
-grep -P '\d+' in > out && fail=1
+# Ensure that \d matches no character.
+returns_ 1 grep -P '\d' in > out || fail=1
 compare /dev/null out || fail=1
 
+# Ensure that ^\D+$ matches the entire line.
+grep -P '^\D+$' in > out || fail=1
+compare in out || fail=1
+
+# When built with PCRE2 10.43 and newer, one may use (?aD) and (?-aD)
+# to toggle between modes.  (?aD) is the default (making \d == [0-9]).
+# (?-aD) relaxes \d, making it match "all" digits.
+# Use mixed digits as input: Arabic 0 and ASCII 4: ٠4
+printf '\331\2404\n' > in2 || framework_failure_
+
+returns_ 1 grep -P '\d\d' in2 > out || fail=1
+compare /dev/null out || fail=1
+
+# The following tests work only when built with 10.43 or newer,
+# with which, grep accepts the mode-setting '(?aD)':
+if echo 0 | grep -qP '(?aD)\d'; then
+
+  grep -P '(?-aD)\d(?aD)\d' in2 > out || fail=1
+  compare in2 out || fail=1
+
+  returns_ 1 grep -P '\d(?-aD)\d' in2 > out || fail=1
+  compare /dev/null out || fail=1
+
+else
+  warn_ 'skipped some tests: use PCRE2 10.43 or newer to enable' \
+    'support for e.g., (?aD) and (?-aD)'
+fi
+
 Exit $fail