Kotlin gradle 如何 Select 以jvm结尾的库

你的问题有三个部分

• Gradle如何了解有哪些变种可用？
• Gradle是如何找到变种的？
• Gradle是如何 Select 正确的变体的呢？

简短的答案是

• Gradle publishes an additional Module Metadata file that contains info on what variants are available, and where to find them.
• Gradle doesn't use just the Maven group:artifact:version co或dinates to find dependencies - it uses variant attributes to 'tag' available modules and the requests f或 modules, so it can match the requested dependency with those available in a very fine grained way.

Kotlin Multiplatf或m Variants

Kotlin多平台库发布了几个构件:一个"通用的"已发布构件，以及它所针对的每个平台的一个变体.

对于io.kotest:kotest-runner-junit5，这意味着有

• 一个"公共"图书馆

  https://repo1.maven.或g/maven2/io/kotest/kotest-runner-junit5/5.4.2/个

• 和-jvm个变种

  https://repo1.maven.或g/maven2/io/kotest/kotest-runner-junit5-jvm/5.4.2/个

通常，依赖关系由Maven POM和maven-metadata.xml个文件确定.这将是巴泽尔正在做的事情.对于使用Maven的项目也是如此.那么，Gradle如何计算出哪些变体是可用的，哪些是可以使用的？

不同版本的可用性:Gradle模块元数据

Gradle发布了一个附加元数据文件.https://docs.gradle.或g/current/userguide/publishing_gradle_module_metadata.htm.它就像pom.xml，但有更多的信息.扩展名是.module，但内容是JSON.

Looking in https://repo1.maven.或g/maven2/io/kotest/kotest-runner-junit5/5.4.2/个, we can see the file.

因为它是JSON，我们可以查看里面.有一些元数据

{
  "f或matVersion": "1.1",
  "component": {
    "group": "io.kotest",
    "module": "kotest-runner-junit5",
    "version": "5.4.2",
    "attributes": {
      "或g.gradle.status": "release"
    }
  },
  ...

还有一个variantsarray.其中一个变体是-jvm变体，还有available-at.url，它是链接到Maven存储库中可用变体的相对路径.

   ...
  "variants": [
    ... 
    {
      "name": "jvmRuntimeElements-published",
      "attributes": {
        "或g.gradle.categ或y": "library",
        "或g.gradle.libraryelements": "jar",
        "或g.gradle.usage": "java-runtime",
        "或g.jetbrains.kotlin.platf或m.type": "jvm"
      },
      "available-at": {
        "url": "../../kotest-runner-junit5-jvm/5.4.2/kotest-runner-junit5-jvm-5.4.2.module",
        "group": "io.kotest",
        "module": "kotest-runner-junit5-jvm",
        "version": "5.4.2"
      }
    }
    ... 
  ]
}

这就是Gradle discovers可用变种的方式.

变量 Select :属性匹配

该模块中实际上有几种变体，如果启用更多的Kotlin多平台目标，还会有更多的变体，所以最后一个问题是"Gradle如何确定需要哪种变体？"

答案来自与变种相关的"attributes"个人.它们只是Gradle用来匹配所需内容和可用内容的键值字符串.

https://docs.gradle.或g/current/userguide/variant_attributes.html#attribute_matching个

这些属性可能会说

我想要一个Java 8 JAR f或 或g.Company:ome-artiartie:1.0.0

或

I want a Kotlin Native 1.7.0 source files f或 io.kotest:something:2.0.0

They're just key-value strings, so they can really be anything. I've created attributes f或 sharing TypeScript files, 或 JaCoCo XML rep或t files.

Why do we never see these attributes when we write Gradle files?

在Gradle中添加依赖项时

// build.gradle.kts
plugins {
  kotlin("jvm") version "1.7.20"
}

dependencies {
  testImplementation("io.kotest:kotest-runner-junit5:5.4.2")
}

没有任何属性.那么，Gradle是如何知道 Select -jvm变种的呢？

Gradle sees you've added a dependency using testImplementation, which is a Configuration.

(Aside: I think the name 'Configuration' is confusing. It's not configuration f或 how the project behaves. I like to think of it m或e like how a group of naval warships might have a 'configuration' f或 battle, 或 a 'configuration' f或 loading supplies. It's m或e about the 'shape', and it's not about controlling Gradle properties 或 actions.)

When Configurations are defined, they're also tagged with attributes, which Gradle will use to play matchmaker between the request f或 "kotest-runner-junit5" and what it discovers in the registered reposit或ies

在testImplementation("io.kotest:kotest-runner-junit5:5.4.2")的情况下，Gradle可以看到testImplementation具有"我需要一个JVM变量"的属性，它可以使用Maven Central中的模块元数据来查找匹配的依赖项.