Idiomatic way to remove/search/change if it has a certain value

[crankydillo]

I need to remove/change a property only if it has a certain value. I think writing an imperative recipe for this won't be that bad, but just making sure there is no current standard way on this. Everything I see in properties just searches by key. Example

[timtebeek]

You could add a precondition using org.openrewrite.properties.ChangePropertyValue, to match the old value and change it to something else.. Only if that produces any changes would the recipeList containing your removal be executed. Hope that's clear and helps!

[crankydillo]

Interesting. So ChangePropertyValue when used as a Precondition won't actually change the property value in the file?

Got to be honest, I never would have thought to do that:) Is this approach documented or widely used?

[timtebeek]

Indeed preconditions never change the actual code; it's what makes this pattern work. :)
Not sure if we've explicitly documented that pattern, but it's certainly helpful here.

[crankydillo]

I was looking at some of the code around Preconditions yesterday. Does what you say work primarily because of the fact that it will not change things and this code:

@Override                                                                                                                                                                                                        
   public @Nullable Tree visit(@Nullable Tree tree, ExecutionContext ctx) {                                                                                                                                         
         Tree t = p.visit(tree, ctx);                                                                                                                                                                                 
         preconditionApplicable = t != tree;                                                                                                                                                                          
         return tree;                                                                                                                                                                                                 
}   

ChangePropertyValue#getVisitor will generate a different Tree in order to actually change the value, so preconditionApplicable will be true?

[timtebeek]

I'm on mobile, but yes that sounds like it to me. It's also why adding a marker works