apple/pkl · error · VmException

cannotFindMember ${key} on object

Error message

cannotFindMember ${key} on object

What it means

Thrown when a subscript/bracket read on a Pkl object does not resolve to any member: the object has no property or element matching the given key. It is Pkl's equivalent of a 'member not found' error for dynamic member reads (`VmUtils.readMemberOrNull` returned null).

Source

Thrown at pkl-core/src/main/java/org/pkl/core/ast/expression/binary/SubscriptNode.java:152

  @Specialization
  protected long eval(VmBytes receiver, long index) {
    if (index < 0 || index >= receiver.getLength()) {
      CompilerDirectives.transferToInterpreter();
      throw exceptionBuilder()
          .evalError("elementIndexOutOfRange", index, 0, receiver.getLength() - 1)
          .withProgramValue("Value", receiver)
          .build();
    }
    return receiver.get(index);
  }

  private Object readMember(VmObject object, Object key, IndirectCallNode callNode) {
    var result = VmUtils.readMemberOrNull(object, key, callNode);
    if (result != null) return result;

    CompilerDirectives.transferToInterpreter();
    throw exceptionBuilder().cannotFindMember(object, key).build();
  }
}

View on GitHub (pinned to f3efcbfc9b)

Solutions

  1. Fix the key name (check the exact spelling in the error)
  2. Declare the property on the object or its class before reading it
  3. Use `obj[key] ?? default` style defaulting where the API allows, or check with `containsKey`-style helpers
  4. Verify the intended amendment/module is actually imported and applied

Example fix

// before
port = config["prot"]
// after
port = config["port"] ?? 8080
Defensive patterns

Strategy: type-guard

Validate before calling

// pkl
exists = obj.hasProperty("key") // or containsKey for mappings
value = if (exists) obj["key"] else default

Type guard

function hasMember(obj, key) { return obj != null && key in obj }

Try / catch

// catch member-not-found and supply a default value

Prevention

When it happens

Trigger: Evaluating `obj[key]` or dynamic member read where `key` matches no property of the object; e.g. reading a config field that was never declared, or a typo in the key name.

Common situations: Typos in config keys, expecting a property added by an amendment that wasn't applied, reading optional fields without a default, schema drift between producer and consumer of a config.

Understand the failure class

Background: Record Not Found Errors: "not found", RecordNotFound, and "was not found" — what they mean and how to fix them — this error's family across 28 libraries.

Related errors

AI-assisted analysis of apple/pkl@f3efcbfc9b (2026-09-08). Data as JSON: /api/errors/e9a486144bf040c9. Report an issue: GitHub.