Treatment of enum based feature flags

[aleksandr-zakshevskii-n26]

Hello, I wanted to get your advice on how to treat the following case,
we have a feature flag which is called FEATURE-A-ENABLED

the code which is using the feature flag:

enum class FeatureFlags(val featureName: String) {
    FEATURE_A("FEATURE-A-ENABLED"),
    FEATURE_B("FEATURE-B-ENABLED")
    ;
}

fun isFeatureEnabled() =
    featureService.isEnabled(FeatureFlags.FEATURE_A)

fun main() {
    if (isFeatureEnabled()) {
        println("Hello world!")
    } else {
        println("Hi world!")
    }
}

Ideally i would like to remove usages of FEATURE_A enum entry and isFeatureEnabled() invocations

enum class FeatureFlags(val featureName: String) {
    FEATURE_B("FEATURE_B")
    ;
}

fun main() {
   println("Hi world!")
}

Initially I tried adding the following rules:

rule #1
delete_enum_declaration - deletes the enum entry using the string "FEATURE-A-ENABLED" , since it's a seed rule I can use the @flag_enum_name in the subsequent non-seed rules

[[rules]]
name = "delete_enum_declaration"
query = """
(
(enum_entry
    (simple_identifier) @flag_enum_name
    (value_arguments
    	(value_argument [
        	(string_literal) @flag_name
     ]))
) @enum_entry
(#eq? @flag_name "\\\"@stale_flag_name\\\"")
)
"""
replace_node = "enum_entry"
replace= ""
groups = ["delete_property_declaration"]
holes = ["stale_flag_name"]

rule #2
replace_flag_method_declaration - deletes one-line functions which are using the FEATURE_A enum entry, in order to use @flag_enum_name from the previous rule this rule must be declared as is_seed_rule = false

[[rules]]
name = "replace_flag_method_declaration"
query = """
(
(function_declaration
    (simple_identifier) @func_name
    (function_body
    	(call_expression
            (navigation_expression (_))
            (call_suffix
            	(value_arguments
                	(value_argument
                    	(navigation_expression
                        	(navigation_suffix
                            	(simple_identifier) @enum_item
                            )))))))) @function_declaration
(#eq? @enum_item "@flag_enum_name")
)
"""
replace_node = "func_name"
replace= ""
groups = ["delete_method_declaration"]
holes = ["flag_enum_name"]
is_seed_rule = false

After running those 2 rules - I get the following result:

enum class FeatureFlags(val featureName: String) {
    FEATURE_B("FEATURE_B")
    ;
}

fun main() {
    if (isFeatureEnabled()) {
        println("Hello world!")
    } else {
        println("Hi world!")
    }
}

As you can see the enum entry and the function declaration isFeatureEnabled are deleted. I want also to replace invocation of isFeatureEnabled() with boolean literal

But from the rules perspective I don't understand how can I accomplish that, since the second rule which matches function declarations - is not a seed rule - so I can't add @function_name to the hole of the 3rd rule. Also I cannot make the 2nd rule as seed, since I need the @ flag_enum_name to identify such functions.

I hope I explained it clearly. I would be appreciated for your help.
Thanks!

[dvmarcilio]

Hi @aleksandr-zakshevskii-n26. Have you tried adding an edge from the 2nd rule to the 3rd rule? In general, if you have rules a and b, and an edge a -> b, you can use matches from a as holes in b.

[aleksandr-zakshevskii-n26]

Hello @dvmarcilio . Thanks a lot, that helped!