我正在尝试使用scala.tools.nsc.interpreter
启用交互式调试(如 Python 的 pdb/ipdb):
val foo = 123
import scala.tools.nsc.Settings
import scala.tools.nsc.interpreter.{ ILoop, SimpleReader }
val repl = new ILoop
repl.settings = new Settings
repl.settings.usejavacp.value = true
repl.in = SimpleReader()
repl.createInterpreter()
repl.intp.bind("foo", "Int", foo)
repl.loop()
repl.closeInterpreter()
运行时,这就是我得到的:
$ scala repl.scala
foo: Int = 123
scala> "hello"
java.lang.NullPointerException
at scala.concurrent.Await$$anonfun$ready$1.apply(package.scala:95)
at scala.concurrent.Await$$anonfun$ready$1.apply(package.scala:95)
at scala.concurrent.BlockContext$DefaultBlockContext$.blockOn(BlockContext.scala:53)
at scala.concurrent.Await$.ready(package.scala:95)
at scala.tools.nsc.interpreter.ILoop.processLine(ILoop.scala:402)
at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:430)
at Main$$anon$1.<init>(repl.scala:14)
at Main$.main(repl.scala:1)
at Main.main(repl.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at scala.reflect.internal.util.ScalaClassLoader$$anonfun$run$1.apply(ScalaClassLoader.scala:70)
at scala.reflect.internal.util.ScalaClassLoader$class.asContext(ScalaClassLoader.scala:31)
at scala.reflect.internal.util.ScalaClassLoader$URLClassLoader.asContext(ScalaClassLoader.scala:101)
at scala.reflect.internal.util.ScalaClassLoader$class.run(ScalaClassLoader.scala:70)
at scala.reflect.internal.util.ScalaClassLoader$URLClassLoader.run(ScalaClassLoader.scala:101)
at scala.tools.nsc.CommonRunner$class.run(ObjectRunner.scala:22)
at scala.tools.nsc.ObjectRunner$.run(ObjectRunner.scala:39)
at scala.tools.nsc.CommonRunner$class.runAndCatch(ObjectRunner.scala:29)
at scala.tools.nsc.ObjectRunner$.runAndCatch(ObjectRunner.scala:39)
at scala.tools.nsc.ScriptRunner.scala$tools$nsc$ScriptRunner$$runCompiled(ScriptRunner.scala:175)
at scala.tools.nsc.ScriptRunner$$anonfun$runScript$1.apply(ScriptRunner.scala:192)
at scala.tools.nsc.ScriptRunner$$anonfun$runScript$1.apply(ScriptRunner.scala:192)
at scala.tools.nsc.ScriptRunner$$anonfun$withCompiledScript$1$$anonfun$apply$mcZ$sp$1.apply(ScriptRunner.scala:161)
at scala.tools.nsc.ScriptRunner$$anonfun$withCompiledScript$1.apply$mcZ$sp(ScriptRunner.scala:161)
at scala.tools.nsc.ScriptRunner$$anonfun$withCompiledScript$1.apply(ScriptRunner.scala:129)
at scala.tools.nsc.ScriptRunner$$anonfun$withCompiledScript$1.apply(ScriptRunner.scala:129)
at scala.tools.nsc.util.package$.trackingThreads(package.scala:43)
at scala.tools.nsc.util.package$.waitingForThreads(package.scala:27)
at scala.tools.nsc.ScriptRunner.withCompiledScript(ScriptRunner.scala:128)
at scala.tools.nsc.ScriptRunner.runScript(ScriptRunner.scala:192)
at scala.tools.nsc.ScriptRunner.runScriptAndCatch(ScriptRunner.scala:205)
at scala.tools.nsc.MainGenericRunner.runTarget$1(MainGenericRunner.scala:67)
at scala.tools.nsc.MainGenericRunner.run$1(MainGenericRunner.scala:87)
at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:98)
at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:103)
at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)
Abandoning crashed session.
scala>
如果我删除该repl.intp.bind("foo", "Int", foo)
部分,这就是我得到的:
$ scala repl.scala
scala> 123
null
Abandoning crashed session.
scala>
我究竟做错了什么?是否有更简单的方法可以在程序运行期间进入交互式 REPL 以进行调试?断点、单步执行和检查本地人有时是不会这样做的。
我在 Scala 2.11.5 上。