hashicorp/nomad · error

value is not known

Error message

value is not known

What it means

CtyValueToMapInterface converts a cty.Value (from ParseHclInterface) into a native Go map. cty unknown values represent values not yet decided (e.g. from expressions or marks); they cannot be materialized, so the helper rejects them up front with this error.

Source

Thrown at helper/pluginutils/hclutils/util.go:73

	value, decDiag := hcldec.Decode(hclFile.Body, spec, evalCtx)
	diag = diag.Extend(decDiag)
	if diag.HasErrors() {
		return cty.NilVal, diag, formattedDiagnosticErrors(diag)
	}

	return value, diag, nil
}

// CtyValueToMapInterface converts a decoded cty value into a Go
// map[string]interface{}.
//
// ParseHclInterface returns a cty.Value and callers sometimes need a generic
// map payload (for example for plugin config maps). This helper converts that
// value recursively into native Go values.
func CtyValueToMapInterface(val cty.Value) (map[string]any, error) {
	if !val.IsKnown() {
		return nil, fmt.Errorf("value is not known")
	}

	if val.IsNull() {
		return nil, nil
	}

	t := val.Type()
	if !t.IsMapType() && !t.IsObjectType() {
		return nil, fmt.Errorf("expected map/object cty value, got %s", t.FriendlyName())
	}

	v, err := ctyValueToInterface(val)
	if err != nil {
		return nil, err
	}

	m, ok := v.(map[string]any)
	if !ok {

View on GitHub (pinned to 482b49bf1a)

Solutions

  1. Evaluate/resolve the HCL expressions so the value is known before converting.
  2. Guard with val.IsKnown() and skip or defer conversion for unknown values.
  3. If validating, treat unknown as 'defer' rather than an error in your caller.

Example fix

// before
m, err := CtyValueToMapInterface(val)
// after
if !val.IsKnown() {
    return nil // skip validation for unknown values
}
m, err := CtyValueToMapInterface(val)
Defensive patterns

Strategy: type-guard

Validate before calling

if !val.IsKnown() {
    return nil // defer validation until value is known
}
mapVal, err := hclutils.CtyValueToMapInterface(val)

Type guard

func isKnownMap(v cty.Value) bool {
    return v.IsKnown() && !v.IsNull() &&
        (v.Type().IsMapType() || v.Type().IsObjectType())
}

Try / catch

m, err := CtyValueToMapInterface(val)
if err != nil && err.Error() == "value is not known" {
    return nil // skip validation for unknown values
} else if err != nil {
    return err
}

Prevention

When it happens

Trigger: Passing a cty.Value whose IsKnown() is false to CtyValueToMapInterface — typically from validatePluginConfig handling plugin config, or HCL containing expressions that evaluate to unknown during validation.

Common situations: Validating plugin configuration where variables/expressions have not been evaluated yet; unit tests covering the Unknown case also exercise this path.

Related errors

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/e7e5eb7b913ebc8d. Report an issue: GitHub.