com.airbnb.epoxy.processor.resourcescanning.JavacResourceScanner.kt Maven / Gradle / Ivy

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Epoxy is a system for composing complex screens with a ReyclerView in Android.
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package com.airbnb.epoxy.processor.resourcescanning

import androidx.room.compiler.processing.XElement
import androidx.room.compiler.processing.XProcessingEnv
import androidx.room.compiler.processing.XTypeElement
import androidx.room.compiler.processing.compat.XConverters.toJavac
import com.squareup.javapoet.ClassName
import com.sun.source.util.Trees
import com.sun.tools.javac.code.Symbol.VarSymbol
import com.sun.tools.javac.tree.JCTree
import com.sun.tools.javac.tree.JCTree.JCFieldAccess
import com.sun.tools.javac.tree.TreeScanner
import java.util.HashMap
import javax.annotation.processing.ProcessingEnvironment
import javax.lang.model.element.AnnotationMirror
import javax.lang.model.element.Element
import javax.lang.model.type.MirroredTypeException
import javax.lang.model.util.Elements
import javax.lang.model.util.Types
import kotlin.reflect.KClass

class JavacResourceScanner(
    processingEnv: ProcessingEnvironment,
    environmentProvider: () -> XProcessingEnv
) : ResourceScanner(environmentProvider) {
    private val typeUtils: Types = processingEnv.typeUtils
    private val elementUtils: Elements = processingEnv.elementUtils
    private var trees: Trees? = null

    init {
        trees = try {
            Trees.instance(processingEnv)
        } catch (ignored: IllegalArgumentException) {
            try {
                // Get original ProcessingEnvironment from Gradle-wrapped one or KAPT-wrapped one.
                // In Kapt, its field is called "delegate". In Gradle's, it's called "processingEnv"
                processingEnv.javaClass.declaredFields.mapNotNull { field ->
                    if (field.name == "delegate" || field.name == "processingEnv") {
                        field.isAccessible = true
                        val javacEnv = field[processingEnv] as ProcessingEnvironment
                        Trees.instance(javacEnv)
                    } else {
                        null
                    }
                }.firstOrNull()
            } catch (ignored2: Throwable) {
                null
            }
        }
    }

    override fun getResourceValueListInternal(
        annotation: KClass,
        element: XElement,
        property: String,
        values: List,
    ): List {
        val results = getResults(annotation.java, element.toJavac())
        return results.values.filter { it.value in values }
    }

    override fun getResourceValueInternal(
        annotation: KClass,
        element: XElement,
        property: String,
        value: Int
    ): ResourceValue? {
        val results = getResults(annotation.java, element.toJavac())
        return if (results.containsKey(value)) {
            results[value]
        } else {
            null
        }
    }

    override fun getImports(classElement: XTypeElement): List {
        return trees?.getPath(classElement.toJavac())
            ?.compilationUnit
            ?.imports?.map { it.qualifiedIdentifier.toString() }
            ?: emptyList()
    }

    private fun getResults(
        annotation: Class,
        element: Element
    ): Map {
        val scanner = AnnotationScanner()
        val tree = trees?.getTree(
            element,
            getMirror(element, annotation)
        ) as JCTree?
        tree?.accept(scanner)
        return scanner.results()
    }

    private inner class AnnotationScanner : TreeScanner() {
        private val results: MutableMap = HashMap()

        override fun visitSelect(jcFieldAccess: JCFieldAccess) {
            val symbol = jcFieldAccess.sym
            if ((symbol as? VarSymbol)?.enclosingElement?.enclosingElement?.enclClass() != null) {
                parseResourceSymbol(symbol)
            }
        }

        private fun parseResourceSymbol(symbol: VarSymbol) {
            // eg com.airbnb.paris.R
            val rClass = symbol.enclosingElement.enclosingElement.enclClass().className()
            // eg styleable
            val rTypeClass = symbol.enclosingElement.simpleName.toString()
            // eg View_background
            val resourceName = symbol.simpleName.toString()
            val value = symbol.constantValue as? Int ?: return
            val androidResourceId =
                ResourceValue(getClassName(rClass, rTypeClass), resourceName, value)
            results[androidResourceId.value] = androidResourceId
        }

        fun results(): Map = results
    }

    private fun getClassName(rClass: String, rTypeClass: String): ClassName {
        val rClassElement: Element? = try {
            elementUtils.getTypeElement(rClass)
        } catch (mte: MirroredTypeException) {
            typeUtils.asElement(mte.typeMirror)
        }
        val rClassPackageName = elementUtils.getPackageOf(rClassElement).qualifiedName.toString()
        return ClassName.get(rClassPackageName, "R", rTypeClass)
    }

    companion object {
        private fun getMirror(
            element: Element,
            annotation: Class
        ): AnnotationMirror? {
            val targetName = annotation.canonicalName
            return element.annotationMirrors.firstOrNull { it.annotationType.toString() == targetName }
        }
    }
}