From 8f295fcb227fba913a6c85d0661f0d60e1ebfc43 Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Fri, 20 Jul 2018 12:59:50 -0400
Subject: [PATCH] CoerceValue should insert Null for unset attrs

This matches the decoder spec, where a value unset in the configuration
is always Null.
---
 configs/configschema/coerce_value.go      |  4 +---
 configs/configschema/coerce_value_test.go | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/configs/configschema/coerce_value.go b/configs/configschema/coerce_value.go
index 1f3793ad11..9c54f158aa 100644
--- a/configs/configschema/coerce_value.go
+++ b/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)
diff --git a/configs/configschema/coerce_value_test.go b/configs/configschema/coerce_value_test.go
index d9b7a17f4a..f0e3552d97 100644
--- a/configs/configschema/coerce_value_test.go
+++ b/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 {