Replace version in yaml structure with regexp - regex

Question

I'm trying to replace the value of the version property in the following yaml structure.
My reason for using regex rather than parsing the yaml is that I need to write it back again. If I parse it and then write it back it'll loose it's existing formatting.
environments:
local:
values:
- kubeContext: default
- surfScreenshotter:
installed: false
version: 0
- whoamiMn:
installed: false
version: 0
dev:
values:
- kubeContext: nuc
- surfScreenshotter:
installed: false
version: 0
- whoamiMn:
installed: false
version: 0
My kotlin code
val regex = """environments:
|.*
| $environment:
| values:
|.*
| - $projectName:
|.*
| {10}version: (\S+)
""".trimMargin().toRegex(MULTILINE)
val updatedHelmfile = regex.replaceFirst(helmfileContent, version)
$environment can be either "local" or "dev" and projectName can be "surfScreenshotter" or "whoamiMn".
Nothing is matched. Anyone got an idea how to make this work?

Answer 1

You can rely on indentation to make sure you are in the right section of your text block and capture the whole part before the version into a capturing group:
val regex = """(environments:
|(?:\R\h{2}.*)*?\R\h{2}$environment:
|(?:\R\h{4}.*)*?\R\h{6}-\h*$projectName:
|(?:\R\h{10}.*)*?\R\h{10}
|version:\h*)\S+
""".trimMargin().toRegex(RegexOption.COMMENTS)
Then, you need to make sure to restore Group 1 contents with $1 in the replacement pattern:
val updatedHelmfile = regex.replaceFirst(helmfileContent, "$1" + version)
See the regex demo and the Kotlin demo.
Details
(environments: - Group 1 start and environments: string
(?:\R\h{2}.*)*?\R\h{2}dev: - zero or more occurrences (as few as possible) of a line break followed with two horizontal whitespace and then the rest of the line, then a line break, two horizontal whitespace and dev: string
(?:\R\h{4}.*)*?\R\h{6}-\h*whoamiMn: - zero or more occurrences (as few as possible) of a line break followed with four horizontal whitespace and then the rest of the line, then a line break, six horizontal whitespace and - + 0 or more spaces, and then whoamiMn: string
(?:\R\h{10}.*)*?\R\h{10} - zero or more occurrences (as few as possible) of a line break followed with ten horizontal whitespace and then the rest of the line, then a line break, ten horizontal whitespace
version:\h*) - version:, 0 or more spaces, end of Group 1
\S+ - one or more non-whitespace chars.