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swift - Type extensions from a framework's dependency available in app

问题描述

OK... this is difficult to explain (and to come up with a title for) but I'll try my best.

We first discovered this when using Carthage to import stuff but setting up a sample project in Xcode (without using Carthage) it seems to have done the same thing.

First, here's a screenshot of the sample project we set up...

enter image description here

The have a target Test20000 and it has a dependency A.

The A framework then has a dependency on B.

Important

The Test20000 app does NOT add B as a direct dependency.

The frameworks

In B there is a struct like...

import Foundation

public struct BType {
    public let value = "Hello, B!"
}

In A there is a file like...

import Foundation
import B

public struct AType {
    public let value = "Hello, A!"

    public func doAThing() {
        print(BType().value)
    }
}

The App

Now in the Test20000 app we do something like...

import Foundation
import A

struct TestType {
    func doSomething() {
        let aType = AType()

        print(aType.value)
        aType.doAThing()
    }
}

This works as expected. It prints...

Hello, A! Hello, B!

If I change the function to something like this...

import Foundation
import A

struct TestType {
    func doSomething() {
        let bType = BType()

        print(bType.value)
    }
}

Then this doesn't compile as B is not imported and so BType can't be accessed.

The catch!

However! If you declare an extension in B something like...

extension String {
    func doAThingInB() {
        print(self)
    }
}

Then now... without any changes to the imports and the dependencies, I can now change my app code to...

import Foundation
import A

struct TestType {
    func doSomething() {
        "Hello, bug!".doAThingInB()
    }
}

And this will print out as though the extension is public to the actual App. It sort of "bunny hops" from B, over A and into the app.

I feel like this shouldn't happen at all.

We can't find a way to turn this off or to stop this happening.

Is this a bug?

Is there something we need to do to stop this?

Thanks

标签： swiftframeworks

解决方案

我曾尝试使用私有模块映射来隐藏内部框架，使其用户不可见A，但没有运气。可能与[SR-2896] 私有模块映射无法正常工作有关。

我想这是现​​在的预期行为。swift.org 论坛上有多个提案可以实现您想要的东西，例如命名空间 x 子模块或更相关的一个@_exported 和修复导入可见性。

上一篇的相关部分：

今天的 Swift 设计得更像 Java、C# 或 Python，因为如果你在 Foo 的实现中导入 Bar，它不会影响导入 Foo 的客户端。或者，它不会让导入 Foo 的客户看到 Bar 的顶级名称。

  1. 您仍然需要 Bar，因为编译器不会跟踪您是否在 Foo 的公共接口中使用了它的一种类型。（这是上一节。）

  2. Bar 中的扩展仍然对导入 Foo 的客户端可见，因为编译器不区分扩展来自今天的位置。

  3. Bar 中的运算符声明仍然对导入 Foo 的客户端可见，因为编译器以不同的方式查找运算符，而不是在顶层查找其他所有内容。

从最后一条消息中：

这个讨论的总体结果是，它可能不值得为 Swift vNext 做任何聪明的事情：只需添加“仅实现导入”和可能的“导出导入”，然后暂时不用管其余部分。

我很高兴知道是否有解决方法，但似乎 没有。

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