Create header mode to enable eliding function / method bodies

[aviroop-123]

• Create -Xheader-mode compiler argument to enable header generation.
• Skip converting function and method body code to FIR.
• Skip inline functions, objects and functions.
• Handle null body during FIR -> IR conversion.
• Handle contracts.
• Disable checkers during header compilation.

More in https://youtrack.jetbrains.com/issue/KT-78422

[ddolovov]

Is this a Kotlin/JVM-only feature?

If yes, then why the CLI flag is available for other Kotlin compilers?

If no, then what's the plan towards the exising -Xheader-klib-path CLI flag in Kotlin/Native?

[aviroop-123]

Is this a Kotlin/JVM-only feature? If yes, then why the CLI flag is available for other Kotlin compilers? If no, then what's the plan towards the exising -Xheader-klib-path CLI flag in Kotlin/Native?

No, we should change the description of the issue. It should work atleast across the JVM and native compiler. Once all the features are implemented, we might be able to deprecate the Xheader-klib-path.

[ddolovov]

I think, it's also important to pass the "header mode" flag down to IrSerializationSettings.publicAbiOnly. This way you can instruct the IR serializer to avoid serializing data that is not part of KLIB ABI, for example, IR element offsets.

[mglukhikh]

I don't see any tests for the feature and it seems quite strange for me. As a very minimum, I'd recommend to add some new tests to compiler/fir/analysis-tests/testData/resolve with the new flag enabled and FIR_DUMP also enabled. This will allow you to check if the necessary body parts (like contracts) are generated and unnecessary parts are not generated.

[mglukhikh]

I think this flag is not needed as you can access it via session.languageVersionSettings.getFlag(...). As an example you can see how it's done for lenientMode. I don't see it's a good idea adding any flag we need as an argument everywhere.