The "%f[set]" frontier pattern has been in Lua 5.1 since the beginning,
but was undocumented until Lua 5.2. And the code is even unchanged from
5.1.0 to 5.2.1. So there's no reason not to implement it in ustring too.
Note the changes to UstringLibrary.php are somewhat large, because it
splits the "convert a Lua bracketed charset to PCRE" code into a
separate function and it changes the handling of mw.ustring.find's and
mw.ustring.match's 'init' parameter from "substring, match from 0, then
add back on $init" to "use preg_match's $offset and use \G instead of ^
where this matters". Both of these are necessary to properly support
%f.
This also fixes a bug in the pure-Lua code (not used in Scribunto)
exposed by the unit tests for %f where %z was matching '\1' rather than
'\0' and %Z everything except '\1' instead of everything except '\0'.
Bug: 48331
Change-Id: Ie0b95ef5b734db53d6adc9de5dae4874f8944c08
This is a reimplementation of Lua's string library with support for
UTF-8.
The entire ustring library is implemented in pure Lua. PHP callbacks are
also available for overrides: in LuaSandbox these are used for almost
all functions, while in LuaStandalone they are used only for the pattern
matching. Also, ustring.upper and ustring.lower are overridden using
mw.language's .uc and .lc if available.
It also includes a bunch of unit tests.
Note that if you download the normalization tests, they may fail under
LuaSandbox if you have PHP's intl extension installed and libicu on your
system is too old.
Change-Id: Ie76fdf8d3a85d0a3d2a41b0d3b7afe433f247af0
