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https://issues.apache.org/jira/browse/GROOVY-10258?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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mgroovy updated GROOVY-10258:
-----------------------------
Priority: Major (was: Minor)
> NPE: Pinpoint Exact Location in Call Chain
> ------------------------------------------
>
> Key: GROOVY-10258
> URL: https://issues.apache.org/jira/browse/GROOVY-10258
> Project: Groovy
> Issue Type: Improvement
> Reporter: mgroovy
> Priority: Major
>
> Groovy should output the exact location where a NullPointerException occurred
> inside a call chain in the NPE message, if possible pretty printed.
> The JVM has been improved in this regard since OpenJDK 14:
> https://openjdk.java.net/jeps/358
> https://www.baeldung.com/java-14-nullpointerexception
> https://bugs.openjdk.java.net/browse/JDK-8233014
> The messages produced alas look pretty ugly for @CompileStatic Groovy (see
> below), due to its predominant use of properties instead of fields, and the
> original goal of JEP 358 to print the complete call chain (access path) seems
> to have been dropped, so it is not particularily helpful in some situations
> (see examples below).
> In Groovy 3.0.9 under OpenJDK 16:
> {code}
> @Newify(pattern=/[A-Z][A-Za-z0-9_]*/)
> //@CompileStatic
> class HelpfulNullPointerExceptionTest {
> static class X {
> X x; String s
> X(X x, String s = null) { this.x = x; this.s = s }
> @Override String toString() { "X($s,$x)" }
> }
> @Test
> void nullPointerInCallChain() {
> final x = X(X(X(X(null,"X-Men"))))
> println "x.x.x.x=$x.x.x.x"
> x.x.x = null
> /*
> * OpenJDK 16 (Eclipse jdk-16.0.2.7-hotspot) (Note:
> -XX:+ShowCodeDetailsInExceptionMessages is now always on by default)
> ** @CompileDynamic: java.lang.NullPointerException: Cannot get
> property 'x' on null object
> ** @CompileStatic: java.lang.NullPointerException: Cannot invoke
> "simple.groovy.HelpfulNullPointerExceptionTest$X.getX()" because the return
> value of "simple.groovy.HelpfulNullPointerExceptionTest$X.getX()" is null
> ** Would hope for something like (or its pretty-printed
> equivalent): java.lang.NullPointerException: Cannot get property 'x.x.x.x' on
> null object
> */
> println "x.x.x.x=$x.x.x.x"
> }
> @Canonical static class A { String a }
> @Canonical static class B { A a }
> @Canonical static class C { B b }
> @Canonical static class D { C c }
> @Test
> void nullPointerInCallChain2() {
> final x = D(C(B(A("aha!"))))
> println "x.c.b.a=$x.c.b.a"
> /*
> * OpenJDK 16 (Eclipse jdk-16.0.2.7-hotspot)
> ** @CompileDynamic: java.lang.NullPointerException: Cannot get
> property 'b' on null object
> ** @CompileStatic: java.lang.NullPointerException: Cannot invoke
> "simple.groovy.HelpfulNullPointerExceptionTest$C.getB()" because the return
> value of "simple.groovy.HelpfulNullPointerExceptionTest$D.getC()" is null
> ** Would hope for something like (or its pretty-printed
> equivalent): java.lang.NullPointerException: Cannot get property 'x.c.b.a' on
> null object
> */
> x.c = null
> println "x.c.b.a=$x.c.b.a"
> }
> }
> {code}
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