如果带注释的成员没有被特定的块包围，则发出IDE警告

Question

我有一个数据结构，它的成员不是线程安全的，调用者需要锁定资源以便适当地读写。下面是一个简单的代码示例:

class ExampleResource : LockableProjectItem {
override val readWriteLock: ReadWriteLock = ReentrantReadWriteLock()
@RequiresReadLock
val nonThreadSafeMember: String = ""
}
interface LockableProjectItem {
val readWriteLock: ReadWriteLock
}
fun <T : LockableProjectItem, Out> T.readLock(block: T.() -> Out): Out {
try {
readWriteLock.readLock().lock()
return block(this)
} finally {
readWriteLock.readLock().unlock()
}
}
fun <T : LockableProjectItem, Out> T.writeLock(block: T.() -> Out): Out {
try {
readWriteLock.writeLock().lock()
return block(this)
} finally {
readWriteLock.writeLock().unlock()
}
}
annotation class RequiresReadLock

调用ExampleResource.nonThreadSafeMember可能看起来像这样:

val resource = ExampleResource()
val readResult = resource.readLock { nonThreadSafeMember }

为了确保调用者知道资源需要被锁定，我希望IDE对任何带有@RequiresReadLock注释且没有被readLock块包围的成员发出警告。有没有办法做到这一点，在IntelliJ编写一个自定义插件的IDE?

Answer 1

我认为这是一种hack，但使用上下文接收器可能会工作。但我不认为它们是用来这样使用的。

您可以声明一个虚拟object作为上下文接收器，并将其作为上下文接收器添加到属性:

object ReadLock
class ExampleResource : LockableProjectItem {
override val readWriteLock: ReadWriteLock = ReentrantReadWriteLock()
// properties with context receivers cannot have a backing field, so we need to explicitly declare this
private val nonThreadSafeMemberField: String = ""
context(ReadLock)
val nonThreadSafeMember: String
get() = nonThreadSafeMemberField
}

然后在readLock中，您传递object:

fun <T : LockableProjectItem, Out> T.readLock(block: context(ReadLock) T.() -> Out): Out {
try {
readWriteLock.readLock().lock()
return block(ReadLock, this)
} finally {
readWriteLock.readLock().unlock()
}
}

指出:

• 如果你试图访问nonThreadSafeMember而没有上下文接收器，将会给你一个错误:

  val resource = ExampleResource()
  val readResult = resource.nonThreadSafeMember //error
  

• 您仍然可以访问nonThreadSafeMember而无需获取读锁，例如:

  with(ReadLock) { // with(ReadLock) doesn't acquire the lock, just gets the context receiver
  resource.nonThreadSafeMember // no error
  }
  

  但是不小心写这样的东西要困难得多，我认为这是你想要防止的。

• 如果你在readLock内部调用另一个函数，并且你想在该函数中访问nonThreadSafeMember，你也应该用context(ReadLock)标记该函数。例如

  fun main() {
  val resource = ExampleResource()
  val readResult = resource.readLock {
  foo(this)
  }
  }
  context(ReadLock)
  fun foo(x: ExampleResource) {
  x.nonThreadSafeMember
  }
  

  上下文接收者通过。