如何解决 ScalaJS 链接中的问题"Fatal error: java.lang.Object is missing called from core module analyzer"

Question

我正试图将ScalaJS链接推迟到运行时，这使得多阶段编译更加灵活，对sbt的依赖更少。

设置如下：

1. 我没有使用scalajs-sbt插件，而是选择直接调用scalajs编译器作为scala编译器插件：

scalaCompilerPlugins("org.scala-js:scalajs-compiler_${vs.scalaV}:${vs.scalaJSV}")

这可以成功地生成"；sjir"；项目输出目录下的文件，但没有其他文件。

2. 使用本文中的解决方案：

在windows机器上使用gradle构建/编译最新的SalaJS(1.3+(？

"链接scala.js自己"要在所有已编译的sjsir文件上调用链接器以生成js文件，这是我的实现：

在编译时&运行时依赖项，添加scalajs基础和scalajs-linker:

bothImpl("org.scala-js:scalajs-library_${vs.scalaBinaryV}:${vs.scalaJSV}")
bothImpl("org.scala-js:scalajs-linker_${vs.scalaBinaryV}:${vs.scalaJSV}")
bothImpl("org.scala-js:scalajs-dom_${vs.scalaJSSuffix}:2.1.0")

编写以下代码：

import org.scalajs.linker.interface.{Report, StandardConfig}
import org.scalajs.linker.{PathIRContainer, PathOutputDirectory, StandardImpl}
import org.scalajs.logging.{Level, ScalaConsoleLogger}
import java.nio.file.{Path, Paths}
import java.util.Collections
import scala.concurrent.duration.Duration
import scala.concurrent.{Await, ExecutionContext}
object JSLinker {
implicit def gec = ExecutionContext.global
def link(classpath: Seq[Path], outputDir: Path): Report = {
val logger = new ScalaConsoleLogger(Level.Warn)
val linkerConfig = StandardConfig() // look at the API of this, lots of options.
val linker = StandardImpl.linker(linkerConfig)
// Same as scalaJSModuleInitializers in sbt, add if needed.
val moduleInitializers = Seq()
val cache = StandardImpl.irFileCache().newCache
val result = PathIRContainer
.fromClasspath(classpath)
.map(_._1)
.flatMap(cache.cached _)
.flatMap(linker.link(_, moduleInitializers, PathOutputDirectory(outputDir), logger))
Await.result(result, Duration.Inf)
}
def linkClasses(outputDir: Path = Paths.get("./")): Report = {
import scala.jdk.CollectionConverters._
val cl = Thread.currentThread().getContextClassLoader
val resources = cl.getResources("")
val rList = Collections.list(resources).asScala.toSeq.map { v =>
Paths.get(v.toURI)
}
link(rList, outputDir)
}
lazy val linkOnce = {
linkClasses()
}
}

资源检测成功，检测到所有包含sjir的根：

rList = {$colon$colon@1629} "::" size = 4
0 = {UnixPath@1917} "/home/peng/git-scaffold/scaffold-gradle-kts/build/classes/scala/test"
1 = {UnixPath@1918} "/home/peng/git-scaffold/scaffold-gradle-kts/build/classes/scala/testFixtures"
2 = {UnixPath@1919} "/home/peng/git-scaffold/scaffold-gradle-kts/build/classes/scala/main"
3 = {UnixPath@1920} "/home/peng/git-scaffold/scaffold-gradle-kts/build/resources/main"

但链接仍然失败：

Fatal error: java.lang.Object is missing
called from core module analyzer

There were linking errors
org.scalajs.linker.interface.LinkingException: There were linking errors
at org.scalajs.linker.frontend.BaseLinker.reportErrors$1(BaseLinker.scala:91)
at org.scalajs.linker.frontend.BaseLinker.$anonfun$analyze$5(BaseLinker.scala:100)
at scala.concurrent.impl.Promise$Transformation.run$$$capture(Promise.scala:467)
at scala.concurrent.impl.Promise$Transformation.run(Promise.scala)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
at java.util.concurrent.ForkJoinTask.doExec$$$capture(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:175)

我想知道这个错误信息意味着什么。显然，java.lang.Object没有被编译成sjir。这个错误消息有意义吗？我该如何修复它？

Answer 1

感谢@sjrd，我现在拥有了正确的运行时编译堆栈。在我的旧设置中有2个问题：

1. 事实证明cl.getResources("")确实无法推断所有类路径，所以我切换到系统属性java.class.path，它包含所有依赖的类路径

2. moduleInitizers必须手动设置为指向一个主方法，该方法将在调用js函数时调用。

更正后，编译类变为：

import org.scalajs.linker.interface.{ModuleInitializer, Report, StandardConfig}
import org.scalajs.linker.{PathIRContainer, PathOutputDirectory, StandardImpl}
import org.scalajs.logging.{Level, ScalaConsoleLogger}
import java.nio.file.{Files, Path, Paths}
import scala.concurrent.duration.Duration
import scala.concurrent.{Await, ExecutionContext, ExecutionContextExecutor}
object JSLinker {
implicit def gec: ExecutionContextExecutor = ExecutionContext.global
val logger = new ScalaConsoleLogger(Level.Info) // TODO: cannot be lazy val, why?
lazy val linkerConf: StandardConfig = {
StandardConfig()
} // look at the API of this, lots of options.
def link(classpath: Seq[Path], outputDir: Path): Report = {
val linker = StandardImpl.linker(linkerConf)
// Same as scalaJSModuleInitializers in sbt, add if needed.
val moduleInitializers = Seq(
ModuleInitializer.mainMethodWithArgs(SlinkyHelloWorld.getClass.getName.stripSuffix("$"), "main")
)
Files.createDirectories(outputDir)
val cache = StandardImpl.irFileCache().newCache
val result = PathIRContainer
.fromClasspath(classpath)
.map(_._1)
.flatMap(cache.cached _)
.flatMap { v =>
linker.link(v, moduleInitializers, PathOutputDirectory(outputDir), logger)
}
Await.result(result, Duration.Inf)
}
def linkClasses(outputDir: Path = Paths.get("./ui/build/js")): Report = {
val rList = getClassPaths
link(rList, outputDir)
}
def getClassPaths: Seq[Path] = {
val str = System.getProperty("java.class.path")
val paths = str.split(':').map { v =>
Paths.get(v)
}
paths
}
lazy val linkOnce: Report = {
val report = linkClasses()
logger.info(
s"""
|=== [Linked] ===
|${report.toString()}
|""".stripMargin
)
report
}
}

这就是将sjsir伪影转换为单个main.js文件所需的全部内容。