protocol-buffers - Protocol Buffers Version 2 中的 "import weak"是什么意思？

Question

Import Statement在 Protocol Buffers Version 2 Language Specification 中有以下文本:

import = "import" [ "weak" | “public”] strLit ";" 

但是Importing Definitions在 Protocol Buffers Version 2 Language Guide 中只谈到了 public 的使用。 import weak 是什么意思？我用谷歌搜索了答案。但我找不到解释。

Answer 1

弱导入是可选的依赖。

请参阅 EnforceWeakDependencies 的文档一些细节:

void DescriptorPool::EnforceWeakDependencies(
        bool enforce)

By default, weak imports are allowed to be missing, in which case we will use a placeholder for the dependency and convert the field to be an Empty message field.

If you call EnforceWeakDependencies(true), however, the DescriptorPool will report a import not found error.