From 558b6dbca7bc933fe01255be9ebeffebd44a2645 Mon Sep 17 00:00:00 2001
From: Mattias Engdegård
Date: Wed, 25 Nov 2020 15:32:08 +0100
Subject: Fix replace-regexp-in-string substring match data translation

For certain patterns, re-matching the same regexp on the matched
substring does not produce correctly translated match data
(bug#15107 and bug#44861).

Using a new builtin function also improves performance since the
number of calls to string-match is halved.

Reported by Kevin Ryde and Shigeru Fukaya.

* lisp/subr.el (replace-regexp-in-string): Translate the match data
using match-data--translate instead of trusting a call to string-match
on the matched string to do the job.
* test/lisp/subr-tests.el (subr-replace-regexp-in-string):
Add test cases.
* src/search.c (Fmatch_data__translate): New internal function.
(syms_of_search): Register it as a subroutine.
---
 src/search.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

(limited to 'src')

diff --git a/src/search.c b/src/search.c
index e7f90949464..4eb634a3c03 100644
--- a/src/search.c
+++ b/src/search.c
@@ -3031,6 +3031,23 @@ If optional arg RESEAT is non-nil, make markers on LIST point nowhere.  */)
   return Qnil;
 }
 
+DEFUN ("match-data--translate", Fmatch_data__translate, Smatch_data__translate,
+       1, 1, 0,
+       doc: /* Add N to all string positions in the match data.  Internal.  */)
+  (Lisp_Object n)
+{
+  CHECK_FIXNUM (n);
+  EMACS_INT delta = XFIXNUM (n);
+  if (EQ (last_thing_searched, Qt))   /* String match data only.  */
+    for (ptrdiff_t i = 0; i < search_regs.num_regs; i++)
+      if (search_regs.start[i] >= 0)
+        {
+          search_regs.start[i] = max (0, search_regs.start[i] + delta);
+          search_regs.end[i] = max (0, search_regs.end[i] + delta);
+        }
+  return Qnil;
+}
+
 /* Called from Flooking_at, Fstring_match, search_buffer, Fstore_match_data
    if asynchronous code (filter or sentinel) is running. */
 static void
@@ -3388,6 +3405,7 @@ is to bind it with `let' around a small expression.  */);
   defsubr (&Smatch_end);
   defsubr (&Smatch_data);
   defsubr (&Sset_match_data);
+  defsubr (&Smatch_data__translate);
   defsubr (&Sregexp_quote);
   defsubr (&Snewline_cache_check);
 
-- 
cgit v1.2.1