CopyDefaultValuesFromExpectLowering.kt
/*
* Copyright 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.compose.compiler.plugins.kotlin.lower
import androidx.compose.compiler.plugins.kotlin.hasComposableAnnotation
import org.jetbrains.kotlin.descriptors.FunctionDescriptor
import org.jetbrains.kotlin.ir.IrStatement
import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
import org.jetbrains.kotlin.ir.declarations.IrFunction
import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
import org.jetbrains.kotlin.resolve.multiplatform.findCompatibleExpectsForActual
/**
* [ComposableFunctionBodyTransformer] relies on presence of default values in
* Composable functions' parameters.
* If Composable function is declared as `expect fun` with default value parameter, then
* [ComposableFunctionBodyTransformer] will not find any default value in `actual fun` - IrFunction.
*
* [CopyDefaultValuesFromExpectLowering] sets default values to parameters of actual functions by
* taking them from their corresponding `expect fun` declarations.
* This lowering needs to run before [ComposableFunctionBodyTransformer] and
* before [ComposerParamTransformer].
*
* Fixes https://github.com/JetBrains/compose-jb/issues/1407
*/
@OptIn(ObsoleteDescriptorBasedAPI::class)
class CopyDefaultValuesFromExpectLowering : ModuleLoweringPass {
override fun lower(module: IrModuleFragment) {
// it uses FunctionDescriptor since current API (findCompatibleExpectedForActual)
// can return only a descriptor
val expectComposables = mutableMapOf<FunctionDescriptor, IrFunction>()
// first pass to find expect functions with default values
module.transformChildrenVoid(object : IrElementTransformerVoid() {
override fun visitFunction(declaration: IrFunction): IrStatement {
if (declaration.isExpect && declaration.hasComposableAnnotation()) {
val hasDefaultValues = declaration.valueParameters.any {
it.defaultValue != null
}
if (hasDefaultValues) {
expectComposables[declaration.descriptor] = declaration
}
}
return super.visitFunction(declaration)
}
})
// second pass to set corresponding default values
module.transformChildrenVoid(object : IrElementTransformerVoid() {
override fun visitFunction(declaration: IrFunction): IrStatement {
if (declaration.descriptor.isActual && declaration.hasComposableAnnotation()) {
val compatibleExpects = declaration.descriptor.findCompatibleExpectsForActual {
module.descriptor == it
}
if (compatibleExpects.isNotEmpty()) {
val expectFun = compatibleExpects.firstOrNull {
it in expectComposables
}?.let {
expectComposables[it]
}
if (expectFun != null) {
declaration.valueParameters.forEachIndexed { index, it ->
it.defaultValue =
it.defaultValue ?: expectFun.valueParameters[index].defaultValue
}
}
}
}
return super.visitFunction(declaration)
}
})
}
}