Jackson 3 breaks `FastDoubleParser` - problem with shading

[m-burst]

We have a project that has FastDoubleParser (ch.randelshofer:fastdoubleparser:2.0.1) as a dependency.

After an upgrade of another dependency transitively brought in Jackson 3.0.1, we saw the following error in our application:

java.lang.NoClassDefFoundError: ch/randelshofer/fastdoubleparser/FastIntegerMath (wrong name: tools/jackson/core/internal/shaded/fdp/FastIntegerMath)
  at java.base/java.lang.ClassLoader.defineClass1(Native Method)
  at java.base/java.lang.ClassLoader.defineClass(Unknown Source)
  at java.base/java.security.SecureClassLoader.defineClass(Unknown Source)
  at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(Unknown Source)
  at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(Unknown Source)
  at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(Unknown Source)
  at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown Source)
  at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
  at ch.randelshofer.fastdoubleparser.FastDoubleMath.tryDecToDoubleWithFastAlgorithm(FastDoubleMath.java:891)
  at ch.randelshofer.fastdoubleparser.FastDoubleMath.tryDecFloatToDoubleTruncated(FastDoubleMath.java:795)
  at ch.randelshofer.fastdoubleparser.JavaDoubleBitsFromCharSequence.valueOfFloatLiteral(JavaDoubleBitsFromCharSequence.java:38)
  at ch.randelshofer.fastdoubleparser.AbstractJavaFloatingPointBitsFromCharSequence.parseDecFloatLiteral(AbstractJavaFloatingPointBitsFromCharSequence.java:184)
  at ch.randelshofer.fastdoubleparser.AbstractJavaFloatingPointBitsFromCharSequence.parseFloatingPointLiteral(AbstractJavaFloatingPointBitsFromCharSequence.java:238)
  at ch.randelshofer.fastdoubleparser.JavaDoubleParser.parseDouble(JavaDoubleParser.java:190)
  at ch.randelshofer.fastdoubleparser.JavaDoubleParser.parseDouble(JavaDoubleParser.java:174)
  at (our code)

I investigated the error and found out that ch/randelshofer/fastdoubleparser/FastIntegerMath.class appears on our classpath twice:

• the correct version inside fastdoubleparser-2.0.1.jar,
• and another version inside jackson-core-3.0.1.jar, which apparently was intended to be shaded, but still appears in the JAR under the original qualified name.

Because of this, if the Jackson JAR appears on the classpath before the FastDoubleParser JAR, FastDoubleParser fails.

[cowtowncoder]

I wonder if this is similar to FasterXML/jackson-modules-base#316 ?

EDIT: does not look like actual duplicates are included. Perhaps some metadata missed by shade plug-in

[cowtowncoder]

@m-burst Which JDK are you observing this with? Looks like there's missing handling of JDK 23+ classes.

[cowtowncoder]

@m-burst I think the issue(s) was fixed via #1501 -- any chance you could verify with jackson-core version 3.0.2-SNAPSHOT?

[m-burst]

I can verify that the issue is indeed fixed in 3.0.2-SNAPSHOT.

We have observed the issue with JDK 24.

Is there a way to make the fix future-proof? For example, if FastDoubleParser adds JDK 25+ specific classes, it will cause a regression on JDK 25+, and this will need to be fixed again.

Alternatively, maybe some kind of CI check can be added to automatically verify that shading works correctly (e.g. that there are no FastDoubleParser classes in their original location)

[m-burst]

For reference, here is my testing code (written in Kotlin):

import java.lang.classfile.ClassFile

fun main() {
    printClasses("ch.randelshofer.fastdoubleparser.FastIntegerMath")
    printClasses("tools.jackson.core.internal.shaded.fdp.FastIntegerMath")
}

private fun printClasses(className: String) {
    val resourceName = className.replace('.', '/') + ".class"
    println("Searching for resource: $resourceName")
    val classLoader = {}::class.java.classLoader
    classLoader.getResources(resourceName).asSequence().forEach { url ->
        println("Found resource: $url")
        println("Class name: ${ClassFile.of().parse(url.readBytes()).thisClass().name()}")
    }
    println()
}

Output with Jackson 3.0.1

Searching for resource: ch/randelshofer/fastdoubleparser/FastIntegerMath.class
Found resource: jar:file:<REDACTED_PATH>/fastdoubleparser-2.0.1.jar!/META-INF/versions/23/ch/randelshofer/fastdoubleparser/FastIntegerMath.class
Class name: ch/randelshofer/fastdoubleparser/FastIntegerMath
Found resource: jar:file:<REDACTED_PATH>/jackson-core-3.0.1.jar!/META-INF/versions/23/ch/randelshofer/fastdoubleparser/FastIntegerMath.class
Class name: tools/jackson/core/internal/shaded/fdp/FastIntegerMath

Searching for resource: tools/jackson/core/internal/shaded/fdp/FastIntegerMath.class
Found resource: jar:file:<REDACTED_PATH>/jackson-core-3.0.1.jar!/META-INF/versions/21/tools/jackson/core/internal/shaded/fdp/FastIntegerMath.class
Class name: tools/jackson/core/internal/shaded/fdp/FastIntegerMath

Output with Jackson 3.0.2-SNAPSHOT

Searching for resource: ch/randelshofer/fastdoubleparser/FastIntegerMath.class
Found resource: jar:file:<REDACTED_PATH>/fastdoubleparser-2.0.1.jar!/META-INF/versions/23/ch/randelshofer/fastdoubleparser/FastIntegerMath.class
Class name: ch/randelshofer/fastdoubleparser/FastIntegerMath

Searching for resource: tools/jackson/core/internal/shaded/fdp/FastIntegerMath.class
Found resource: jar:file:<REDACTED_PATH>/jackson-core-3.0.2-SNAPSHOT.jar!/META-INF/versions/23/tools/jackson/core/internal/shaded/fdp/FastIntegerMath.class
Class name: tools/jackson/core/internal/shaded/fdp/FastIntegerMath