Merge pull request #28067 from hashicorp/alisdair/defaults-fix-null-structural-types

functions: Fix defaults for null objects/tuples

Author: alisdair

lang/funcs/defaults.go

@@ -94,6 +94,16 @@ func defaultsApply(input, fallback cty.Value) cty.Value {
 		return v
 
 	case wantTy.IsObjectType():
+		// For structural types, a null input value must be passed through. We
+		// do not apply default values for missing optional structural values,
+		// only their contents.
+		//
+		// We also pass through the input if the fallback value is null. This
+		// can happen if the given defaults do not include a value for this
+		// attribute.
+		if input.IsNull() || fallback.IsNull() {
+			return input
+		}
 		atys := wantTy.AttributeTypes()
 		ret := map[string]cty.Value{}
 		for attr, aty := range atys {
@@ -107,6 +117,17 @@ func defaultsApply(input, fallback cty.Value) cty.Value {
 		return cty.ObjectVal(ret)
 
 	case wantTy.IsTupleType():
+		// For structural types, a null input value must be passed through. We
+		// do not apply default values for missing optional structural values,
+		// only their contents.
+		//
+		// We also pass through the input if the fallback value is null. This
+		// can happen if the given defaults do not include a value for this
+		// attribute.
+		if input.IsNull() || fallback.IsNull() {
+			return input
+		}
+
 		l := wantTy.Length()
 		ret := make([]cty.Value, l)
 		for i := 0; i < l; i++ {

lang/funcs/defaults_test.go

@@ -370,6 +370,79 @@ func TestDefaults(t *testing.T) {
 			Defaults: cty.StringVal("hello"),
 			WantErr:  `only object types and collections of object types can have defaults applied`,
 		},
+		// When applying default values to structural types, null objects or
+		// tuples in the input should be passed through.
+		{
+			Input: cty.ObjectVal(map[string]cty.Value{
+				"a": cty.NullVal(cty.Object(map[string]cty.Type{
+					"x": cty.String,
+					"y": cty.String,
+				})),
+				"b": cty.NullVal(cty.Tuple([]cty.Type{cty.String, cty.String})),
+			}),
+			Defaults: cty.ObjectVal(map[string]cty.Value{
+				"a": cty.ObjectVal(map[string]cty.Value{
+					"x": cty.StringVal("hello"),
+					"y": cty.StringVal("there"),
+				}),
+				"b": cty.TupleVal([]cty.Value{
+					cty.StringVal("how are"),
+					cty.StringVal("you?"),
+				}),
+			}),
+			Want: cty.ObjectVal(map[string]cty.Value{
+				"a": cty.NullVal(cty.Object(map[string]cty.Type{
+					"x": cty.String,
+					"y": cty.String,
+				})),
+				"b": cty.NullVal(cty.Tuple([]cty.Type{cty.String, cty.String})),
+			}),
+		},
+		// When applying default values to structural types, we permit null
+		// values in the defaults, and just pass through the input value.
+		{
+			Input: cty.ObjectVal(map[string]cty.Value{
+				"a": cty.ListVal([]cty.Value{
+					cty.ObjectVal(map[string]cty.Value{
+						"p": cty.StringVal("xyz"),
+						"q": cty.StringVal("xyz"),
+					}),
+				}),
+				"b": cty.SetVal([]cty.Value{
+					cty.TupleVal([]cty.Value{
+						cty.NumberIntVal(0),
+						cty.NumberIntVal(2),
+					}),
+					cty.TupleVal([]cty.Value{
+						cty.NumberIntVal(1),
+						cty.NumberIntVal(3),
+					}),
+				}),
+				"c": cty.NullVal(cty.String),
+			}),
+			Defaults: cty.ObjectVal(map[string]cty.Value{
+				"c": cty.StringVal("tada"),
+			}),
+			Want: cty.ObjectVal(map[string]cty.Value{
+				"a": cty.ListVal([]cty.Value{
+					cty.ObjectVal(map[string]cty.Value{
+						"p": cty.StringVal("xyz"),
+						"q": cty.StringVal("xyz"),
+					}),
+				}),
+				"b": cty.SetVal([]cty.Value{
+					cty.TupleVal([]cty.Value{
+						cty.NumberIntVal(0),
+						cty.NumberIntVal(2),
+					}),
+					cty.TupleVal([]cty.Value{
+						cty.NumberIntVal(1),
+						cty.NumberIntVal(3),
+					}),
+				}),
+				"c": cty.StringVal("tada"),
+			}),
+		},
 		// When applying default values to collection types, null collections in the
 		// input should result in empty collections in the output.
 		{