Compilation customizer is not called during compilation of groovy DSL script - groovy

Question

I want to write a groovy DSL with syntax:
returnValue when booleanCondition
I want to use compilation customizers to transform this expression to a typical if return statement using AST transformations.
For this script:
2 when 1 == 1
I get exception message:
MultipleCompilationErrorsException: startup failed:
Script1.groovy: 1: expecting EOF, found '1' # line 1, column 8.
I don't understand why my compilation customizer is not called at all?
I need it to be called before compilation so I can make it into a valid groovy code.
If the script contains valid groovy code, then my compilation customizer is called.
My code:
class MyDslTest {
public static void main(String[] args) {
String script = '''2 when 1 == 1
'''
def compilerConfig = new CompilerConfiguration()
compilerConfig.addCompilationCustomizers(new MyCompilationCustomizer())
GroovyShell groovyShell = new GroovyShell(compilerConfig)
groovyShell.evaluate(script)
}
}
class MyCompilationCustomizer extends CompilationCustomizer {
MyCompilationCustomizer() {
super(CompilePhase.CONVERSION)
}
#Override
void call(SourceUnit source, GeneratorContext context, ClassNode classNode) throws CompilationFailedException {
println 'in compilation customizer'
}
}

Answer 1

The problem is that your code is not syntactically valid. A compilation customizer will not workaround that: to be able to get an AST, on which the customizer will work, you have to produce syntactically correct code. One option is to use a different AntlrParserPlugin, but in general I don't recommend to do it because it will modify the sources before parsing, and therefore create a mismatch between the AST and the actual source.