Groovy ConfigSlurper: how to modify a closure in a config? - grails

Question

I want to modify a grails BuildConfig.groovy:
grails.project.dependency.resolution = {
plugins {
build ":tomcat:7.0.50"
// plugins for the compile step
compile ":scaffolding:2.0.1"
compile ':cache:1.1.1'
// plugins needed at runtime but not for compilation
runtime ":hibernate:3.6.10.7" // or ":hibernate4:4.1.11.6"
runtime ":database-migration:1.3.8"
runtime ":jquery:1.10.2.2"
runtime ":resources:1.2.1"
}
}
Especially I want to add a plugin and modify another one.
I tried it with ConfigSlurper:
def conf = new ConfigSlurper().parse(new File(buildConfig).toURL())
def plugins = conf.grails.project.dependency.resolution
println "found plugins: $plugins"
plugins.each {
println it
}
The access to conf.grails.project.dependency works fine but conf.grails.project.dependency.resolution is a closure and I don't know how to access or even modify this section.

Answer 1

I don't know grails enough to make some opinionated guess, but it seems to me this config file doesn't conform to ConfigSlurper expected syntax. If what you want to parse isn't very long, you can try intercepting it yourself:
class PluginConfig {
def compileLibs = []
def runtimeLibs = []
def version
def build(version) { this.version = version }
def compile(lib) { compileLibs << lib }
def runtime(lib) { runtimeLibs << lib }
}
def conf = new ConfigSlurper().parse(new File("BuildConfig.groovy").toURL())
def plugins = conf.grails.project.dependency.resolution
def lib = new PluginConfig()
plugins.delegate = lib // magick!!
plugins()
assert lib.compileLibs == [":scaffolding:2.0.1", ':cache:1.1.1']
assert lib.runtimeLibs == [
":hibernate:3.6.10.7",
":database-migration:1.3.8",
":jquery:1.10.2.2",
":resources:1.2.1"
]
assert lib.version == ":tomcat:7.0.50"
No idea how to rewrite this to a file (easily) after the change, though. Maybe using Grails own config parser might be a better idea; it must have a representation of the config when it parses the file.

Answer 2

As far as I know there is no perfect way for doing this: all available parsers/slurpers drop the comments of your configuration. So even if you would modify the result from the config slurper and write it back, it wouldn't be what you are looking for.
You also have t consider that people might use variables for version numbers and other unexpected stuff.
So I guess the best way to modify the config is to use some regular expressions and hope that you users have a standard configuration...