Skip to content

Forcing values with toMap in dependency loop situations can emit null values from VmObject.iterateAlreadyForcedMemberValues #1181

New issue
New issue
Open
Open
Forcing values with toMap in dependency loop situations can emit null values from VmObject.iterateAlreadyForcedMemberValues#1181
@sin-ack

Description

@sin-ack
sin-ack
opened on Aug 20, 2025

Reproduced in Pkl 0.29.0.

I don't really have a reproducer for this, as the failure happens in an internal codebase which I am not allowed to share and I haven't been able to create an independent reproduction that exhibits the error. This is an approximation of how the code looks (but does not reproduce the error):

// --- meta.pkl ---
amends "PackageMetadata.pkl"

name = "package"

packages {
    ["package"] {
        meta = (import("meta.pkl")) {}
        definition = (import("definition.pkl")) {}
    }
}

// --- definition.pkl ---
extends "PackageDefinition.pkl"

import "DockerContainerTask.pkl"
import "DockerNetworkTask.pkl"

import "meta.pkl"

tasks {
    ["Docker"] {
        local docker = this

        ["network"] = new DockerNetworkTask {
            name = "network"
        }

        ["backend"] = new DockerContainerTask {
            name = "backend"
            image = "backend"
            networks { docker["network"].asNetwork(meta.self) }
        }

        ["other"] = new DockerContainerTask {
            name = "other"
            image = "other"
        }
    }
}

// --- PackageMetadata.pkl ---
module PackageMetadata

import "PackageDefinition.pkl"
import "PackageMetadata.pkl"

name: String
packages: Mapping<String, Package>

hidden fixed self = packages[name]

class Package {
    meta: PackageMetadata
    definition: PackageDefinition

    function absoluteName(providerName: String, taskName: String): String =
        let (provider = definition.tasks.getOrNull(providerName))
        if (provider == null) throw("Package '\(this.meta.name)' does not support provider '\(providerName)'")
        else
            // v Error happens here, in `filter`
            let (task = provider.toMap().values.filter((t) -> t.name == taskName).firstOrNull)
            if (task == null) throw("Package '\(meta.name)' does not contain task '\(taskName)' in provider '\(providerName)'")
            else "\(meta.name)-\(taskName)"
}

// --- PackageDefinition.pkl ---
open module PackageDefinition

import "Task.pkl"

tasks: Mapping<String, Mapping<String, Task>>

// --- Task.pkl ---
abstract module Task

name: String

// --- DockerContainerTask.pkl ---
module DockerContainerTask

extends "Task.pkl"

import "DockerNetwork.pkl"

image: String
networks: Listing<DockerNetwork> = new { }

// --- DockerNetworkTask.pkl ---
module DockerNetworkTask

extends "Task.pkl"

import "PackageMetadata.pkl"
import "DockerNetwork.pkl"

driver: String = "bridge"

/// Return this task as a `DockerNetwork`. [package] must be the package this
/// task is defined in.
function asNetwork(package: PackageMetadata.Package) = new DockerNetwork {
    kind = "External"
    name = package.absoluteName("Docker", outer.name)
}

// --- DockerNetwork.pkl ---
module DockerNetwork

typealias NetworkKind = "Internal" | "External"

name: String
kind: NetworkKind = "Internal"

When I evaluate definition.pkl in the internal codebase, I get the following Pkl error (stack trace redacted/modified to fit the code example):

org.pkl.core.PklBugException: An unexpected error has occurred. Would you mind filing a bug report?
Cmd+Double-click the link below to open an issue.
Please copy and paste the entire error output into the issue's description.

https://github.com/apple/pkl/issues/new

java.lang.NullPointerException

–– Pkl Error ––
None (cause has no message)

52 | let (task = provider.toMap().values.filter((t) -> t.name == taskName).firstOrNull)
                                                ^^^^^^^^^^^^^^^^^^^^^^^^^
at PackageMetadata#Package.absoluteName.<function#3> (PackageMetadata.pkl)

52 | let (task = provider.toMap().values.filter((t) -> t.name == taskName).firstOrNull)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at PackageMetadata#Package.absoluteName.<function#1> (PackageMetadata.pkl)

49 | let (provider = definition.tasks.getOrNull(providerName))
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at PackageMetadata#Package.absoluteName (PackageMetadata.pkl)

31 | name = Package.absoluteName("Docker", outer.name)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at DockerNetworkTask#asNetwork.name (DockerNetworkTask.pkl)

Pkl 0.30.0-dev+dbcd11da (Linux 6.15.3-cachyos, native)

java.lang.NullPointerException
        at org.pkl.core.ast.expression.member.ReadPropertyNodeGen.executeGeneric(ReadPropertyNodeGen.java:78)
        at org.pkl.core.ast.expression.binary.EqualNodeGen.executeGeneric_generic5(EqualNodeGen.java:205)
        at org.pkl.core.ast.expression.binary.EqualNodeGen.executeGeneric(EqualNodeGen.java:93)
        at org.pkl.core.ast.member.FunctionNode.executeImpl(FunctionNode.java:116)
        at org.pkl.core.ast.PklRootNode.execute(PklRootNode.java:46)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.executeRootNode(OptimizedCallTarget.java:776)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.profiledPERoot(OptimizedCallTarget.java:700)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callBoundary(OptimizedCallTarget.java:624)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.invokeCallBoundary(SubstrateOptimizedCallTarget.java:124)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTargetInstalledCode.doInvoke(SubstrateOptimizedCallTargetInstalledCode.java:232)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.doInvoke(SubstrateOptimizedCallTarget.java:106)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callDirect(OptimizedCallTarget.java:556)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedDirectCallNode.call(OptimizedDirectCallNode.java:94)
        at org.pkl.core.ast.lambda.ApplyVmFunction1Node.evalDirect(ApplyVmFunction1Node.java:80)
        at org.pkl.core.ast.lambda.ApplyVmFunction1NodeGen.execute(ApplyVmFunction1NodeGen.java:71)
        at org.pkl.core.ast.lambda.ApplyVmFunction1Node.executeBoolean(ApplyVmFunction1Node.java:41)
        at org.pkl.core.stdlib.base.ListNodes$filter.eval(ListNodes.java:430)
        at org.pkl.core.stdlib.base.ListNodesFactory$filterNodeGen.executeAndSpecialize(ListNodesFactory.java:3297)
        at org.pkl.core.stdlib.base.ListNodesFactory$filterNodeGen.executeGeneric(ListNodesFactory.java:3286)
        at org.pkl.core.ast.member.FunctionNode.executeImpl(FunctionNode.java:116)
        at org.pkl.core.ast.PklRootNode.execute(PklRootNode.java:46)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.executeRootNode(OptimizedCallTarget.java:776)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.profiledPERoot(OptimizedCallTarget.java:700)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callBoundary(OptimizedCallTarget.java:624)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.invokeCallBoundary(SubstrateOptimizedCallTarget.java:124)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTargetInstalledCode.doInvoke(SubstrateOptimizedCallTargetInstalledCode.java:232)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.doInvoke(SubstrateOptimizedCallTarget.java:106)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callDirect(OptimizedCallTarget.java:556)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedDirectCallNode.call(OptimizedDirectCallNode.java:94)
        at org.pkl.core.ast.expression.member.InvokeMethodVirtualNode.evalCached(InvokeMethodVirtualNode.java:134)
        at org.pkl.core.ast.expression.member.InvokeMethodVirtualNodeGen.executeAndSpecialize(InvokeMethodVirtualNodeGen.java:272)
        at org.pkl.core.ast.expression.member.InvokeMethodVirtualNodeGen.executeGeneric(InvokeMethodVirtualNodeGen.java:193)
        at org.pkl.core.ast.expression.member.ReadPropertyNodeGen.executeGeneric(ReadPropertyNodeGen.java:73)
        at org.pkl.core.ast.expression.binary.LetExprNode.executeGeneric(LetExprNode.java:71)
        at org.pkl.core.ast.expression.ternary.IfElseNode.executeGeneric(IfElseNode.java:49)
        at org.pkl.core.ast.member.FunctionNode.executeImpl(FunctionNode.java:116)
        at org.pkl.core.ast.PklRootNode.execute(PklRootNode.java:46)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.executeRootNode(OptimizedCallTarget.java:776)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.profiledPERoot(OptimizedCallTarget.java:700)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callBoundary(OptimizedCallTarget.java:624)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.invokeCallBoundary(SubstrateOptimizedCallTarget.java:124)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTargetInstalledCode.doInvoke(SubstrateOptimizedCallTargetInstalledCode.java:232)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.doInvoke(SubstrateOptimizedCallTarget.java:106)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callDirect(OptimizedCallTarget.java:556)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedDirectCallNode.call(OptimizedDirectCallNode.java:94)
        at org.pkl.core.ast.expression.binary.LetExprNode.executeGeneric(LetExprNode.java:73)
        at org.pkl.core.ast.member.FunctionNode.executeImpl(FunctionNode.java:116)
        at org.pkl.core.ast.PklRootNode.execute(PklRootNode.java:46)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.executeRootNode(OptimizedCallTarget.java:776)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.profiledPERoot(OptimizedCallTarget.java:700)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callBoundary(OptimizedCallTarget.java:624)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.invokeCallBoundary(SubstrateOptimizedCallTarget.java:124)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTargetInstalledCode.doInvoke(SubstrateOptimizedCallTargetInstalledCode.java:232)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.doInvoke(SubstrateOptimizedCallTarget.java:106)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callDirect(OptimizedCallTarget.java:556)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedDirectCallNode.call(OptimizedDirectCallNode.java:94)
        at org.pkl.core.ast.expression.member.InvokeMethodVirtualNode.evalCached(InvokeMethodVirtualNode.java:134)
        at org.pkl.core.ast.expression.member.InvokeMethodVirtualNodeGen.executeAndSpecialize(InvokeMethodVirtualNodeGen.java:272)
        at org.pkl.core.ast.expression.member.InvokeMethodVirtualNodeGen.executeGeneric(InvokeMethodVirtualNodeGen.java:193)
        at org.pkl.core.ast.member.TypeCheckedPropertyNode.evalTypedObjectCached(TypeCheckedPropertyNode.java:54)
        at org.pkl.core.ast.member.TypeCheckedPropertyNodeGen.executeAndSpecialize(TypeCheckedPropertyNodeGen.java:136)
        at org.pkl.core.ast.member.TypeCheckedPropertyNodeGen.executeImpl(TypeCheckedPropertyNodeGen.java:101)
        at org.pkl.core.ast.PklRootNode.execute(PklRootNode.java:46)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.executeRootNode(OptimizedCallTarget.java:776)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.profiledPERoot(OptimizedCallTarget.java:700)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callBoundary(OptimizedCallTarget.java:624)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.invokeCallBoundary(SubstrateOptimizedCallTarget.java:124)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTargetInstalledCode.doInvoke(SubstrateOptimizedCallTargetInstalledCode.java:232)
        at org.graalvm.truffle.runtime.svm/com.oracle.svm.truffle.api.SubstrateOptimizedCallTarget.doInvoke(SubstrateOptimizedCallTarget.java:106)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.callDirect(OptimizedCallTarget.java:556)
        at org.graalvm.truffle.runtime/com.oracle.truffle.runtime.OptimizedCallTarget.call(OptimizedCallTarget.java:502)
        at org.graalvm.truffle/com.oracle.truffle.api.nodes.IndirectCallNode$1.call(IndirectCallNode.java:96)
        at org.pkl.core.runtime.VmUtils.doReadMember(VmUtils.java:312)
        at org.pkl.core.runtime.VmUtils.doReadMember(VmUtils.java:214)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:177)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:197)
        at org.pkl.core.runtime.VmValue.force(VmValue.java:67)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:185)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:197)
        at org.pkl.core.runtime.VmValue.force(VmValue.java:67)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:185)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:197)
        at org.pkl.core.runtime.VmValue.force(VmValue.java:67)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:185)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:197)
        at org.pkl.core.runtime.VmValue.force(VmValue.java:67)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:185)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:197)
        at org.pkl.core.runtime.VmValue.force(VmValue.java:67)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:185)
        at org.pkl.core.runtime.VmObject.force(VmObject.java:197)
        at org.pkl.core.runtime.VmValue.force(VmValue.java:67)
        at org.pkl.server.BinaryEvaluator.evaluate$lambda$2(BinaryEvaluator.kt:63)
        at org.pkl.core.EvaluatorImpl.lambda$doEvaluate$15(EvaluatorImpl.java:368)
        at org.pkl.core.EvaluatorImpl.doEvaluate(EvaluatorImpl.java:316)
        at org.pkl.core.EvaluatorImpl.doEvaluate(EvaluatorImpl.java:364)
        at org.pkl.server.BinaryEvaluator.evaluate(BinaryEvaluator.kt:59)
        at org.pkl.server.Server.handleEvaluate$lambda$2(Server.kt:128)
        at [email protected]/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
        at [email protected]/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
        at [email protected]/java.lang.Thread.runWith(Thread.java:1596)
        at [email protected]/java.lang.Thread.run(Thread.java:1583)
        at org.graalvm.nativeimage.builder/com.oracle.svm.core.thread.PlatformThreads.threadStartRoutine(PlatformThreads.java:896)
        at org.graalvm.nativeimage.builder/com.oracle.svm.core.thread.PlatformThreads.threadStartRoutine(PlatformThreads.java:872)

I dug through the VM code a bit, and it seems at this particular line null is returned:

pkl/pkl-core/src/main/java/org/pkl/core/runtime/VmObject.java

Lines 130 to 132 in 3f2f0c3

Object cachedValue = getCachedValue(key);
assert cachedValue != null; // forced
return consumer.accept(key, member, cachedValue);

Which then results in a Java null which is untrace()able. Indeed, if I enable assertions in jpkl, the assert below it triggers.
I'm not sure what exactly is causing forcing to fail like this, but presumably Pkl should either outright reject the toMap because of the dependency loop (definition -> DockerNetworkTask -> meta -> definition) or allow partial forcing.

Metadata

Metadata

Assignees

No one assigned

    Labels

    No labels
    No labels

    Type

    No type

    Projects

    No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions