Replace version in yaml structure with regexp

user_672009 0
Viewed 337

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?

kotlin regex
1 Answers

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.
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