apple/pkl · error · VmException

methodNotDefined1

methodNotDefined1

Error message

methodNotDefined1

What it means

ExternalMethod1Node is the Truffle node base class for Pkl stdlib methods taking one argument. If no type-specialized execution path matches the (receiver class, argument class) pair, the @Fallback method runs and throws the "methodNotDefined1" eval error, naming the qualified member and the argument's actual class. It means the stdlib method does not support that argument type.

Solutions

1. Read the error's reported argument class and compare with the method's documented parameter type.
2. Convert the argument explicitly: `.toInt()`, `.toString()`, `.toRegex()`, etc., before the call.
3. Check for null/unset propagation — use the null-coalescing or `??` default to supply a correct value.
4. Verify the method overload exists in your Pkl version's stdlib docs.

Example fix

// before
names.joinToString(sep)
// after (when sep is accidentally an Int count)
names.joinToString(sep.toString())

// Pkl: assert the argument type before the stdlib call
assert(isString(sep), "joinToString separator must be a String")

function isString(x) = x is String
// also: x is Int, x != null checks before the call

When it happens

Trigger: Calling a one-argument stdlib method (e.g. a List/Map/String method) with an argument whose type is not in its overload set — e.g. passing a String where an Int is expected, or null, or a concrete object/Class where a Function was expected.

Common situations: Config typo passing the wrong property; value became null due to an earlier default; Pkl version change where a type overload was removed; passing `this` or a module where a simpler type was expected.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• methodNotDefined2
• methodNotDefined3
• methodNotDefined4
• methodNotDefined5
• cannotExportValue

AI-assisted analysis of apple/pkl@f3efcbfc9b (2026-09-08). Data as JSON: /api/errors/5017bdb5c4f84c48. Report an issue: GitHub.

Appendix: source

Thrown at pkl-core/src/main/java/org/pkl/core/stdlib/ExternalMethod1Node.java:31

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.pkl.core.stdlib;

import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
import com.oracle.truffle.api.dsl.Fallback;
import com.oracle.truffle.api.dsl.NodeChild;
import org.pkl.core.ast.ExpressionNode;
import org.pkl.core.runtime.VmUtils;

@NodeChild(value = "arg1Node", type = ExpressionNode.class)
public abstract class ExternalMethod1Node extends ExternalMethodNode {
  public abstract ExpressionNode getArg1Node();

  @Fallback
  @TruffleBoundary
  protected Object fallback(@SuppressWarnings("unused") Object receiver, Object argument) {
    throw exceptionBuilder()
        .evalError("methodNotDefined1", getQualifiedMemberName(), VmUtils.getClass(argument))
        .withProgramValue("Argument", argument)
        .build();
  }

  public interface Factory {
    ExternalMethod1Node create(ExpressionNode receiverNode, ExpressionNode arg1Node);
  }
}

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