What's the best way to achieve this? ```// Transfo...

# compiler

[Leland Takamine]

What's the best way to achieve this?

// Transform all instances of this call...
foo()

// ...into this via a compiler plugin:
foo("Hello")

I'm playing around with CallResolutionInterceptorExtension but wondering if there are any other extensions I should be looking at.

[jereksel]

If you are sure method with the same name and string parameter exists, you can use ExpressionCodegenExtension - but it's JVM only

[jereksel]

You could also use IR manipulation, but I haven't done that - I know arrow Meta is using that.

[Leland Takamine]

Awesome thanks! I'll dig into that. If you happen to know of a good example using ExpressionCodegenExtension to alter a function call let me know!

[Leland Takamine]

I'm sure there's a number of things I'm doing wrong here but would appreciate any pointers:

class FooExpressionCodegenExtension(private val project: Project) : ExpressionCodegenExtension {

    override fun applyFunction(
        receiver: StackValue,
        resolvedCall: ResolvedCall<*>,
        c: ExpressionCodegenExtension.Context
    ): StackValue? {
        val newExpression = KtPsiFactory(project).createExpression("foo()")
        return c.codegen.gen(newExpression)
    }
}

With the code above I'm getting the following error:

No resolved call for 'foo()' at (2,1) in dummy.kt

I've taken a look at some different API's and it seems like I'm always getting stuck figuring out how to provide a ResolvedCall . Are there any examples I can take a look at to figure this out or is there any tribal knowledge that anyone can provide here?

[Leland Takamine]

Same result with

return StackValue.expression(
            Type.getMethodType("()V"),
            KtPsiFactory(project).createExpression("foo()"),
            c.codegen
        )

[jereksel]

The only examples I know are Android Extensions:
https://github.com/JetBrains/kotlin/blob/master/plugins/android-extensions/android-extensions-compiler/src/org/jetbrains/kotlin/android/synthetic/codegen/AbstractAndroidExtensionsExpressionCodegenExtension.kt
https://github.com/JetBrains/kotlin/blob/master/plugins/android-extensions/android-extensions-compiler/src/org/jetbrains/kotlin/android/parcel/ParcelableCodegenExtension.kt

and my own plug-in:
https://github.com/jereksel/jailbreakk/blob/master/kotlin-plugin/src/main/kotlin/com/jereksel/jailbreakk/JailbreakkExpressionCodegenExtension.kt

I'll see if I can cook up example for you.

[jereksel]

Also, what are you trying to achieve? Codegen is usually used for generating custom declarations, not rewriting existing ones.

[jereksel]

Here you go: https://github.com/jereksel/leland-compiler-plugin-example - there are some unchecked casts and unsafe null dropping, but it works fine.

[Leland Takamine]

Thank you this is super helpful! I'm trying to implement a prototype of a something similar to Swifts #line / #file / #function / etc macros:

// Swift 
func logFunctionName(string: String = #function) {
    print(string)
}
func myFunction() {
    logFunctionName() // Prints "myFunction()".
}

[Leland Takamine]

I feel like it would have been really difficult to figure out on my own what you've implemented in that example. Are there any resources available to learn more about these APIs?