These are useful methods in groovy that give you control over
the replacements used:
```
'the quick brown fox'.replaceAll(/[aeiou]/,
m -> m.group().toUpperCase(Locale.ROOT))
```
Perviously we used token level lookbehind in the parser. That worked,
but only if the parser didn't have any ambiguity *at all*. Since the
parser has ambiguity it didn't work everywhere. In particular it failed
when parsing blocks in lambdas like `a -> {int b = a + 2; b * b}`.
This moves the hack from the parser into the lexer. There we can use
token lookbehind (same trick) to *insert* semicolons into the token
stream. This works much better for antlr because antlr's prediction
code can work with real tokens.
Also, the lexer is simpler than the parser, so if there is a place
to introduce a hack, that is a better place.
Painless: Add support for //m
Painless: Add support for //s
Painless: Add support for //i
Painless: Add support for //u
Painless: Add support for //U
Painless: Add support for //l
This means "literal" and is exposed for completeness sake with
the java api.
Painless: Add support for //c
c enables Java's CANON_EQ (canonical equivalence) flag which makes
unicode characters that are canonically equal match. Java's javadoc
gives "a\u030A" being equal to "\u00E5". That is that the "a" code
point followed by the "combining ring above" code point is equal to
the "a with combining ring above" code point.
Update docs and add multi-flag test
Whitelist most of the Pattern class.
Adds support for the find operator (=~) and the match operator (==~)
to painless's regexes. Also whitelists most of the Matcher class and
documents regex support in painless.
The find operator (=~) returns a boolean that is the result of building
a matcher on the lhs with the Pattern on the RHS and calling `find` on
it. Use it like this:
```
if (ctx._source.last =~ /b/)
```
The match operator (==~) returns boolean like find but instead of calling
`find` on the Matcher it calls `matches`.
```
if (ctx._source.last ==~ /[^aeiou].*[aeiou]/)
```
Finally, if you want the actual matcher you do:
```
Matcher m = /[aeiou]/.matcher(ctx._source.last)
```
Registering a script engine or native scripts still uses Guice today
and is much more complicated than needed. This change moves to a pull
based model where script plugins have to implement a dedicated interface
`ScriptPlugin` and defines simple getter returning instances rather than
classes.