How can I use regex to convert Uppercase text to lowercase text in combination with a look-ahead and look-behind

Question

In the context of an XML file, I want to use the XML tags in a positive look-behind and positive look-ahead to convert a value to lowercase.

BEFORE:

<CONDITION NAME="ABC-DEF-GHI" DATE="DATE">

AFTER:

<CONDITION NAME="abc-def-ghi" DATE="DATE">

Pattern's tried from other questions/regex wiki that don't work.

1.

FIND:    
(?<=(<CONDITION NAME="))(.+)(?=(" DATE="DATE"))
REPLACE:
\L0

FIND:    
(?<=(<CONDITION NAME=".*))(\w)(?=(.*" DATE="DATE"))
REPLACE:
\L$1

Using VS Code 1.62.1 MAC OS Darwin x64 19.6.0

Answer 1

Make sure you make the other groups non-capturing:

(?<=(?:<CONDITION NAME="))(.+)(?=(?:" DATE="DATE"))

Or leave out the inner () altogether:

(?<=<CONDITION NAME=")(.+)(?=" DATE="DATE")

Or use $2 as replacement. Everything between standard () becomes a captured group, no matter where in the expression they are.

And be careful with .+, in this case [^"]+ is a much safer choice.

Answer 2

You don't need any capture groups if yo want to use lookarounds at the left and right side.

Instead of using .+ which is a broad match and can match too much, you can use a negated character class [^"]+ to match any character except a double quote, or you can use [\w-]+ to match 1 or more word characters or a hyphen:

(?<=<CONDITION NAME=")[^"]+(?=" DATE="DATE")

Regex demo

Replace with the full match using $0

\L$0

---

Another option is to use 2 capture groups with a single lookahead as lookarounds can be expensive, and replace with $1\L$2

(<CONDITION NAME=")([\w-]+)(?=" DATE="DATE")

Answer 3

Pattern 2 works. The replace value just needs to change from \L$1 -> \L$2

Pattern 1 could also be used with \L$2 as the replace value.

This pattern works: FIND:
(?<=(<CONDITION NAME=".*))(\w)(?=(.*" DATE="DATE")) REPLACE: \L$2