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How to explicitly select a Java method overload? #37
Description
When calling a Java method from JS, if multiple overloads are applicable, the runtime correctly complains that it can't choose (please forgive the nonsensical example):
$ js --jvm
> Graal
{language: "JavaScript", versionJS: "1.0", versionGraalVM: "1.0.0-rc5", isGraalRuntime: true}
> java.lang.Runtime.getRuntime().exec(null)
TypeError: INVOKE on JavaObject[java.lang.Runtime@799f10e1 (java.lang.Runtime)] failed due to: java.lang.IllegalArgumentException: Multiple applicable overloads found for method name exec (candidates: [Method[public java.lang.Process java.lang.Runtime.exec(java.lang.String[]) throws java.io.IOException], Method[public java.lang.Process java.lang.Runtime.exec(java.lang.String) throws java.io.IOException]], arguments: [DynamicObject<null>@18078bef (DynamicObjectBasic)])
at <js> :program(<shell>:3:1:0-35)
This is in line with Nashorn:
$ jjs -version
nashorn 1.8.0_121
jjs> java.lang.Runtime.getRuntime().exec(null)
java.lang.RuntimeException: java.lang.NoSuchMethodException: Can't unambiguously select between fixed arity signatures [(java.lang.String), (java.lang.String[])] of the method java.lang.Runtime.exec for argument types [null]
However Nashorn lets us pick an overload to resolve the ambiguity:
jjs> java.lang.Runtime.getRuntime()["exec(java.lang.String)"](null)
java.lang.NullPointerException
Trying the same syntax in GraalJS doesn't work:
> java.lang.Runtime.getRuntime()["exec(java.lang.String)"](null)
TypeError: (intermediate value).lang.Runtime.getRuntime(...)["exec(java.lang.String)"] is not a function
at <js> :program(<shell>:8:1:56-61)
The lookupOverloadByParamTypeString method:
https://github.com/graalvm/graaljs/blob/69bc58643bf77ed6eaaaffca3e79beb4b473a664/graal-js/src/com.oracle.truffle.js.runtime/src/com/oracle/truffle/js/runtime/interop/JavaMethod.java#L504
looks promising but I have no idea how to invoke it. Ideally, the Nashorn syntax would be supported…
Activity
Experimental explicit overload resolver
woess commentedon Dec 7, 2020
java.lang.Runtime.getRuntime()["exec(java.lang.String)"]is supported since 21.0.0.