terraform: mapping overrides work

terraform/context.go

@@ -332,6 +332,13 @@ func (c *Context) computeVars(raw *config.RawConfig) error {
 			val, ok := c.variables[v.Name]
 			if ok {
 				vs[n] = val
+				continue
+			}
+
+			for k, val := range c.variables {
+				if strings.HasPrefix(k, v.Name+".") {
+					vs["var."+k] = val
+				}
 			}
 		}
 	}

terraform/context_test.go

@@ -1045,7 +1045,8 @@ func TestContextApply_vars(t *testing.T) {
 			"aws": testProviderFuncFixed(p),
 		},
 		Variables: map[string]string{
-			"foo": "us-west-2",
+			"foo":            "us-west-2",
+			"amis.us-east-1": "override",
 		},
 	})
 

terraform/terraform_test.go

@@ -222,6 +222,7 @@ const testTerraformApplyVarsStr = `
 aws_instance.bar:
   ID = foo
   bar = foo
+  baz = override
   foo = us-west-2
   type = aws_instance
 aws_instance.foo:

terraform/test-fixtures/apply-vars/main.tf

@@ -17,4 +17,5 @@ resource "aws_instance" "foo" {
 resource "aws_instance" "bar" {
     foo = "${var.foo}"
     bar = "${lookup(var.amis, var.foo)}"
+    baz = "${var.amis.us-east-1}"
 }