Function GetAttr

ops.go:266–393

GetAttr is a helper function that performs the same operation as the attribute access in the HCL expression language. That is, the result is the same as it would be for obj.attr in a configuration expression. This is exported so that applications can access attributes in a manner consistent with ho

(obj cty.Value, attrName string, srcRange *Range)

// though nil can be provided if the calling application is going to
// ignore the subject of the returned diagnostics anyway.
func GetAttr(obj cty.Value, attrName string, srcRange *Range) (cty.Value, Diagnostics) {
	if obj.IsNull() {
		return cty.DynamicVal, Diagnostics{
			{
				Severity: DiagError,
				Summary:  "Attempt to get attribute from null value",
				Detail:   "This value is null, so it does not have any attributes.",
				Subject:  srcRange,
			},
		}
	}

	const unsupportedAttr = "Unsupported attribute"

	ty := obj.Type()
	switch {
	case ty.IsObjectType():
		if !ty.HasAttribute(attrName) {
			return cty.DynamicVal, Diagnostics{
				{
					Severity: DiagError,
					Summary:  unsupportedAttr,
					Detail:   fmt.Sprintf("This object does not have an attribute named %q.", attrName),
					Subject:  srcRange,
				},
			}
		}

		if !obj.IsKnown() {
			return cty.UnknownVal(ty.AttributeType(attrName)).WithSameMarks(obj), nil
		}

		return obj.GetAttr(attrName), nil
	case ty.IsMapType():
		if !obj.IsKnown() {
			return cty.UnknownVal(ty.ElementType()).WithSameMarks(obj), nil
		}

		idx := cty.StringVal(attrName)

		// Here we drop marks from HasIndex result, in order to allow basic
		// traversal of a marked map in the same way we can traverse a marked
		// object
		hasIndex, _ := obj.HasIndex(idx).Unmark()
		if hasIndex.False() {
			return cty.DynamicVal, Diagnostics{
				{
					Severity: DiagError,
					Summary:  "Missing map element",
					Detail:   fmt.Sprintf("This map does not have an element with the key %q.", attrName),
					Subject:  srcRange,
				},
			}
		}

		return obj.Index(idx), nil
	case ty == cty.DynamicPseudoType:
		return cty.DynamicVal.WithSameMarks(obj), nil