Gradle 5.0 在 buid.gradle.kts 中使用 Kotlin DSL 时导致错误 Val cannot be reassigned

Question

这个错误确实 不是 发生在 gradle 版本 4.10.2

行classDirectories = files(filesToCover)导致 gradle 抛出错误:

* What went wrong:
Script compilation error:

  Line 80:             classDirectories = files(filesToCover)
                       ^ Val cannot be reassigned

但是当你查看底层 Java 类时 JacocoReportBase您可以清楚地看到有一个 setter 并且类属性不是最终的。

public abstract class JacocoReportBase extends JacocoBase {
    private FileCollection executionData;
    private FileCollection sourceDirectories;
    private FileCollection classDirectories;
    private FileCollection additionalClassDirs;
    private FileCollection additionalSourceDirs;

    ...

    public void setClassDirectories(FileCollection classDirectories) {
        this.classDirectories = classDirectories;
    }

build.gradle.kts

tasks {
    withType<KotlinCompile<KotlinJvmOptions>> {
        kotlinOptions.freeCompilerArgs = listOf("-Xjsr305=strict")
        kotlinOptions.jvmTarget = "1.8"
    }

    withType<JacocoReport> {
        reports {
            xml.isEnabled = false
            csv.isEnabled = false
            html.destination = file("$buildDir/jacocoHtml")
        }

        afterEvaluate {
            val filesToAvoidForCoverage = listOf(
                    "/dto",
                    "/config",
                    "AuthenticationMicroServiceKt.class"
            )
            val filesToCover = mutableListOf<String>()
            File("build/classes/kotlin/main/app/example/core/")
                    .walkTopDown()
                    .mapNotNull { file ->
                        var match = false
                        filesToAvoidForCoverage.forEach {
                            if (file.absolutePath.contains(it)) {
                                match = true
                            }
                        }
                        return@mapNotNull if (!match) {
                            file.absolutePath
                        } else {
                            null
                        }
                    }
                    .filter { it.contains(".class") }
                    .toCollection(filesToCover)

            classDirectories = files(filesToCover) // error
        }
    }
}

我还在 Github here 上发布了一个问题

Answer 1

来看看the source code :

/**
 * Source sets that coverage should be reported for.
 */
@PathSensitive(PathSensitivity.RELATIVE)
@InputFiles
public ConfigurableFileCollection getClassDirectories() {
    return classDirectories;
}

/**
 * Classes that coverage should be reported for.
 * @deprecated Use {@code getClassDirectories().setFrom(...)}
 */
@Deprecated
public void setClassDirectories(FileCollection classDirectories) {
    DeprecationLogger.nagUserOfDiscontinuedMethod("JacocoReportBase.setClassDirectories(FileCollection)", "Use getClassDirectories().from(...)");
    this.classDirectories.setFrom(classDirectories);
}

如您所见， getClassDirectories返回类型为 ConfigurableFileCollection和 setClassDirectories接受 FileCollection .所以这不是一个有效的 Java Beans 属性，因为 getter 和 setter 对不同的类型进行操作。所以 Kotlin 只能看到 getter，实际上它是 val .

您可以尝试调用 setClassDirectories直接( setClassDirectories(…) 而不是 classDirectories = … )，或使用 classDirectories.setFrom ，正如 Javadocs 所建议的那样。

它在 4.10.2 中工作，因为它 was a property at that time (getter 和 setter 类型相同)。 this commit 中的情况发生了变化.