Merge pull request #18508 from hashicorp/jbardin/config-nulls

always use Null for unset configuration values

configs/configschema/coerce_value.go

@@ -58,9 +58,7 @@ func (b *Block) coerceValue(in cty.Value, path cty.Path) (cty.Value, error) {
 		switch {
 		case ty.HasAttribute(name):
 			val = in.GetAttr(name)
-		case attrS.Computed:
-			val = cty.UnknownVal(attrS.Type)
-		case attrS.Optional:
+		case attrS.Computed || attrS.Optional:
 			val = cty.NullVal(attrS.Type)
 		default:
 			return cty.UnknownVal(b.ImpliedType()), path.NewErrorf("attribute %q is required", name)

configs/configschema/coerce_value_test.go

@@ -342,6 +342,22 @@ func TestCoerceValue(t *testing.T) {
 			cty.DynamicVal,
 			`.foo: number required`,
 		},
+		"unset computed value": {
+			&Block{
+				Attributes: map[string]*Attribute{
+					"foo": {
+						Type:     cty.String,
+						Optional: true,
+						Computed: true,
+					},
+				},
+			},
+			cty.ObjectVal(map[string]cty.Value{}),
+			cty.ObjectVal(map[string]cty.Value{
+				"foo": cty.NullVal(cty.String),
+			}),
+			``,
+		},
 	}
 
 	for name, test := range tests {

configs/configschema/decoder_spec.go

@@ -2,7 +2,6 @@ package configschema
 
 import (
 	"github.com/hashicorp/hcl2/hcldec"
-	"github.com/zclconf/go-cty/cty"
 )
 
 var mapLabelNames = []string{"key"}
@@ -11,9 +10,8 @@ var mapLabelNames = []string{"key"}
 // using the facilities in the hcldec package.
 //
 // The returned specification is guaranteed to return a value of the same type
-// returned by method ImpliedType, but it may contain null or unknown values if
-// any of the block attributes are defined as optional and/or computed
-// respectively.
+// returned by method ImpliedType, but it may contain null values if any of the
+// block attributes are defined as optional and/or computed respectively.
 func (b *Block) DecoderSpec() hcldec.Spec {
 	ret := hcldec.ObjectSpec{}
 	if b == nil {
@@ -21,30 +19,10 @@ func (b *Block) DecoderSpec() hcldec.Spec {
 	}
 
 	for name, attrS := range b.Attributes {
-		switch {
-		case attrS.Computed && attrS.Optional:
-			// In this special case we use an unknown value as a default
-			// to get the intended behavior that the result is computed
-			// unless it has been explicitly set in config.
-			ret[name] = &hcldec.DefaultSpec{
-				Primary: &hcldec.AttrSpec{
-					Name: name,
-					Type: attrS.Type,
-				},
-				Default: &hcldec.LiteralSpec{
-					Value: cty.UnknownVal(attrS.Type),
-				},
-			}
-		case attrS.Computed:
-			ret[name] = &hcldec.LiteralSpec{
-				Value: cty.UnknownVal(attrS.Type),
-			}
-		default:
-			ret[name] = &hcldec.AttrSpec{
-				Name:     name,
-				Type:     attrS.Type,
-				Required: attrS.Required,
-			}
+		ret[name] = &hcldec.AttrSpec{
+			Name:     name,
+			Type:     attrS.Type,
+			Required: attrS.Required,
 		}
 	}
 

configs/configschema/decoder_spec_test.go

@@ -55,6 +55,11 @@ func TestBlockDecoderSpec(t *testing.T) {
 						Optional: true,
 						Computed: true,
 					},
+					"optional_computed_unknown": {
+						Type:     cty.String,
+						Optional: true,
+						Computed: true,
+					},
 				},
 			},
 			hcltest.MockBody(&hcl.BodyContent{
@@ -67,14 +72,19 @@ func TestBlockDecoderSpec(t *testing.T) {
 						Name: "optional_computed_overridden",
 						Expr: hcltest.MockExprLiteral(cty.True),
 					},
+					"optional_computed_unknown": {
+						Name: "optional_computed_overridden",
+						Expr: hcltest.MockExprLiteral(cty.UnknownVal(cty.String)),
+					},
 				},
 			}),
 			cty.ObjectVal(map[string]cty.Value{
 				"optional":                     cty.NullVal(cty.Number),
 				"required":                     cty.StringVal("5"), // converted from number to string
-				"computed":                     cty.UnknownVal(cty.List(cty.Bool)),
-				"optional_computed":            cty.UnknownVal(cty.Map(cty.Bool)),
+				"computed":                     cty.NullVal(cty.List(cty.Bool)),
+				"optional_computed":            cty.NullVal(cty.Map(cty.Bool)),
 				"optional_computed_overridden": cty.True,
+				"optional_computed_unknown":    cty.UnknownVal(cty.String),
 			}),
 			0,
 		},