make fish compatible with pcre2 10.21

pcre2_substitute() now sets the output buffer length to PCRE2_UNSET (~0)
if the output buffer is determined to be too small. This change keeps
track of the buffer size separately where pcre2 can't touch it.

A better fix would be to let pcre2 tell fish what size buffer it needs.
This can be done with PCRE2_SUBSTITUTE_OVERFLOW_LENGTH, but this
requires pcre2 10.21 or later (released January 12), which may be too
new to introduce as a dependency at this point.

Fixes #2743

2 files changed, 3 insertions, 0 deletions

diff --git a/tests/string.in b/tests/string.in
index 1c78e2b3..8afc97ff 100644
--- a/tests/string.in
+++ b/tests/string.in
@@ -55,6 +55,8 @@ string replace -r '(\w+)\s+(\w+)' '$2 $1 $$' 'left right'
 
 string replace -r '\s*newline\s*' '\n' 'put a newline here'
 
+string replace -r -a '(\w)' '$1$1' ab
+
 # test some failure cases
 string match -r '[' 'a[sd' 2>/dev/null; or echo "invalid expression error"
 
diff --git a/tests/string.out b/tests/string.out
index 64b956e3..45ccb369 100644
--- a/tests/string.out
+++ b/tests/string.out
@@ -41,6 +41,7 @@ spaces_to_underscores
 right left $
 put a
 here
+aabb
 invalid expression error
 invalid argument error
 missing argument returns 0