Add filter for instructions inlined by Kotlin compiler

[Godin]

Fixes #763

After this change for the same example as in #763 :

$ java -jar jacococli.jar classinfo --verbose CallsiteKt.class
  INST   BRAN   LINE   METH   CXTY   ELEMENT
     7      0      4      2      2   class 0xcc96f697bc87baa7 CallsiteKt
     6      0      3      1      1   +- method main([Ljava/lang/String;)V
     1      0                        |  +- line 2
     1      0                        |  +- line 3
     1      0                        |  +- line 4
     1      0      1      1      1   +- method nop()V
     1      0                           +- line 7

[Godin]

@marchof could you please do first review pass?

[Godin]

@jwalter thanks a lot for testing and this valuable feedback just in time to keep our master free from bugs 👍 our small team really appreciates this ❤️

Don't know yet how to reproduce this, but apparently KotlinDebug section is not always present in SMAP. Will try to do a deeper look and fix later today.

[jwalter]

Not sure it helps, but the class triggering looks like this (lines 8-20. 1-7 are package declaration and imports):

internal class GetFormTemplateBodyBuilder: BodyBuilder<GetFormTemplateType> {
  override fun buildElement(mediatorRequest: MediatorClientRequest): JAXBElement<GetFormTemplateType> {
    val getFormsRequest = ObjectFactory().createGetFormTemplateType().apply {
      subjectOfCare = mediatorRequest.subjectOfCare()
      assert(subjectOfCare != null) { "No patient id provided" }
      sessionID = mediatorRequest.correlationId
      assert(sessionID != null) { "No correlation id provided" }
      templateID = mediatorRequest.getParameter("id")
      assert(templateID != null) { "No template id provided" }
    }
    return ObjectFactory().createGetFormTemplate(getFormsRequest)
  }
}

[Godin]

@jwalter thank you for the code - it gave an idea about reproducer, which is actually quite simple:

compilation of

fun main(args: Array<String>) {
    assert(args.size < 0) {
        println("Ouch")
    }
} // line 5

results in

...
        17: getstatic     #21                 // Field kotlin/_Assertions.ENABLED:Z
        20: ifeq          53
...
      LineNumberTable:
        line 2: 6
        line 3: 27
        line 4: 37
        line 2: 40
        line 5: 53
...
SourceDebugExtension:
  SMAP
  Example.kt
  Kotlin
  *S Kotlin
  *F
  + 1 Example.kt
  ExampleKt
  *L
  1#1,6:1
  *E

Will work on a fix in context of this ticket.

However this is also quite interesting in context of a #654 (comment) (CC @goodwinnk @yole): content of assert function clearly becomes inlined (see above bytecode at offsets 17 and 20), however there doesn't seem to be a way to determine this from SMAP as it doesn't mention AssertionsJVM.kt.

[Godin]

And here is another example:

F1.kt

package example

inline fun call(crossinline init: () -> Unit) {
    return {
        init()
    }()
} // line 7

F2.kt

package example

fun test(): String {
    var res = "Fail"
    call {
        res = "OK"
    }
    return res
}

that produces F2Kt$test$$inlined$call$1.class without KotlinDebug strata, however with line numbers that go beyond line numbers in source file F1.kt

...
  public final void invoke();
    descriptor: ()V
    flags: ACC_PUBLIC, ACC_FINAL
    Code:
      stack=2, locals=2, args_size=1
         0: nop
         1: aload_0
         2: getfield      #18                 // Field $res$inlined:Lkotlin/jvm/internal/Ref$ObjectRef;
         5: ldc           #34                 // String OK
         7: putfield      #40                 // Field kotlin/jvm/internal/Ref$ObjectRef.element:Ljava/lang/Object;
        10: nop
        11: return
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            1       9     1 $i$a$1$call   I
            0      12     0  this   Lorg/jacoco/core/test/validation/kotlin/targets/F2Kt$test$$inlined$call$1;
      LineNumberTable:
        line 5: 0
        line 9: 1
        line 10: 10
        line 6: 11
...
SourceFile: "F1.kt"
SourceDebugExtension:
  SMAP
  F1.kt
  Kotlin
  *S Kotlin
  *F
  + 1 F1.kt
  org/jacoco/core/test/validation/kotlin/targets/F1Kt$call$1
  + 2 F2.kt
  org/jacoco/core/test/validation/kotlin/targets/F2Kt
  *L
  1#1,8:1
  6#2,2:9
  *E

From which to me seems that we can change algorithm on following:
in LineSection of main Kotlin strata
find minimal OutputStartLine
excluding LineInfos whose LineFileID corresponds to SourceFile attribute.

• for the above example this means: ignore 1#1,8:1 and from 6#2,2:9 take 9
• this obviously also works for the previous example (Add filter for instructions inlined by Kotlin compiler #764 (comment)): ignore the only existing 1#1,6:1
• for current validation test: ignore 1#1,33:1 and from 22#1,2:34 take 34
• for initial example (Add filter for instructions inlined by Kotlin compiler #763 (comment)): ignore 1#1,8:1, from 2#2,2:9 and 2#3,2:11 take 9

Any feedback/thoughts about this new algorithm are welcome.

[Godin]

I was wrong about current validation test 😞

object KotlinInlineTarget { // line 19

    inline fun inlined() {
        nop()
    }

    @JvmStatic
    fun main(args: Array<String>) {

        inlined()

    }

} // line 32

SMAP
KotlinInlineTarget.kt
Kotlin
*S Kotlin
*F
+ 1 KotlinInlineTarget.kt
org/jacoco/core/test/validation/kotlin/targets/KotlinInlineTarget
*L
1#1,33:1
22#1,2:34
*E
*S KotlinDebug
*F
+ 1 KotlinInlineTarget.kt
org/jacoco/core/test/validation/kotlin/targets/KotlinInlineTarget
*L
28#1,2:34
*E

[Godin]

 excluding `LineInfo`s whose `LineFileID` corresponds to `SourceFile` attribute
+and `InputStartLine` equal to `OutputStartLine`

stale

[Godin]

@jwalter could you please retest?

[jwalter]

@Godin Works great! (My coverage went from 40% to 90%)

[Godin]

@jwalter thanks a lot for testing! 👍 ❤️

Please excuse me for pedantism, but as a remark - when talking about metrics it is IMO very important to always specify metric, i.e. percentage of what? "instructions"? 😉

Nevertheless, while #763 initially is about mismatch between numbers of lines in XML report and source files, another aspect - is indeed a fix of metrics (instructions, lines, branches, complexity), which before this change were including inlined code that potentially comes from other libraries and therefore doesn't require tests on a side of consumers of library.

Thanks again for spotting bug and testing! ❤️ Hope there won't be other obstacles and we'll publish this soon.