terraform: validation with unknown variables works [GH-432]

terraform/context.go

@@ -1069,6 +1069,9 @@ func (c *walkContext) validateWalkFn() depgraph.WalkFunc {
 				l.Unlock()
 			}
 
+			// Compute the variables in this resource
+			rn.Resource.Config.interpolate(c, rn.Resource)
+
 			log.Printf("[INFO] Validating resource: %s", rn.Resource.Id)
 			ws, es := rn.Resource.Provider.ValidateResource(
 				rn.Resource.Info.Type, rn.Resource.Config)
@@ -1451,6 +1454,11 @@ func (c *walkContext) computeVars(
 				}
 			}
 		case *config.ModuleVariable:
+			if c.Operation == walkValidate {
+				vs[n] = config.UnknownVariableValue
+				continue
+			}
+
 			value, err := c.computeModuleVariable(v)
 			if err != nil {
 				return err
@@ -1476,6 +1484,11 @@ func (c *walkContext) computeVars(
 				vs[n] = c.Context.module.Config().Dir
 			}
 		case *config.ResourceVariable:
+			if c.Operation == walkValidate {
+				vs[n] = config.UnknownVariableValue
+				continue
+			}
+
 			var attr string
 			var err error
 			if v.Multi && v.Index == -1 {
@@ -1495,6 +1508,11 @@ func (c *walkContext) computeVars(
 				continue
 			}
 
+			if c.Operation == walkValidate {
+				vs[n] = config.UnknownVariableValue
+				continue
+			}
+
 			// Look up if we have any variables with this prefix because
 			// those are map overrides. Include those.
 			for k, val := range c.Variables {

terraform/context_test.go

@@ -499,6 +499,53 @@ func TestContextValidate_selfRefMultiAll(t *testing.T) {
 	}
 }
 
+func TestContextValidate_varRef(t *testing.T) {
+	m := testModule(t, "validate-variable-ref")
+	p := testProvider("aws")
+	c := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	computed := false
+	p.ValidateResourceFn = func(t string, c *ResourceConfig) ([]string, []error) {
+		computed = c.IsComputed("foo")
+		return nil, nil
+	}
+
+	c.Validate()
+	if !computed {
+		t.Fatal("should be computed")
+	}
+}
+
+func TestContextValidate_varRefFilled(t *testing.T) {
+	m := testModule(t, "validate-variable-ref")
+	p := testProvider("aws")
+	c := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		Variables: map[string]string{
+			"foo": "bar",
+		},
+	})
+
+	var value interface{}
+	p.ValidateResourceFn = func(t string, c *ResourceConfig) ([]string, []error) {
+		value, _ = c.Get("foo")
+		return nil, nil
+	}
+
+	c.Validate()
+	if value != "bar" {
+		t.Fatalf("bad: %#v", value)
+	}
+}
+
 func TestContextInput(t *testing.T) {
 	input := new(MockUIInput)
 	m := testModule(t, "input-vars")

terraform/test-fixtures/validate-variable-ref/main.tf

@@ -0,0 +1,5 @@
+variable "foo" {}
+
+resource "aws_instance" "bar" {
+    foo = "${var.foo}"
+}