Nested lists and maps fail in GetRaw

When referencing a list of maps variable from within a resource, only
the first list element is included the plan. This is because GetRaw
can't access the interpolated values. Add some tests to document this
behavior for both Get and GetRaw.

terraform/resource_test.go

@@ -172,6 +172,42 @@ func TestResourceConfigGet(t *testing.T) {
 			Value: nil,
 		},
 
+		// Reference list of maps variable.
+		// This does not work from GetRaw.
+		{
+			Vars: map[string]interface{}{
+				"maplist": []interface{}{
+					map[string]interface{}{
+						"key": "a",
+					},
+					map[string]interface{}{
+						"key": "b",
+					},
+				},
+			},
+			Config: map[string]interface{}{
+				"maplist": "${var.maplist}",
+			},
+			Key:   "maplist.0",
+			Value: map[string]interface{}{"key": "a"},
+		},
+
+		// Reference a map-of-lists variable.
+		// This does not work from GetRaw.
+		{
+			Vars: map[string]interface{}{
+				"listmap": map[string]interface{}{
+					"key1": []interface{}{"a", "b"},
+					"key2": []interface{}{"c", "d"},
+				},
+			},
+			Config: map[string]interface{}{
+				"listmap": "${var.listmap}",
+			},
+			Key:   "listmap.key1",
+			Value: []interface{}{"a", "b"},
+		},
+
 		// FIXME: this is ambiguous, and matches the nested map
 		//        leaving here to catch this behaviour if it changes.
 		{
@@ -270,6 +306,92 @@ func TestResourceConfigGet(t *testing.T) {
 	}
 }
 
+func TestResourceConfigGetRaw(t *testing.T) {
+	cases := []struct {
+		Config map[string]interface{}
+		Vars   map[string]interface{}
+		Key    string
+		Value  interface{}
+	}{
+		// Referencing a list-of-maps variable doesn't work from GetRaw.
+		// The ConfigFieldReader currently catches this case and looks up the
+		// variable in the config.
+		{
+			Vars: map[string]interface{}{
+				"maplist": []interface{}{
+					map[string]interface{}{
+						"key": "a",
+					},
+					map[string]interface{}{
+						"key": "b",
+					},
+				},
+			},
+			Config: map[string]interface{}{
+				"maplist": "${var.maplist}",
+			},
+			Key:   "maplist.0",
+			Value: nil,
+		},
+		// Reference a map-of-lists variable.
+		// The ConfigFieldReader currently catches this case and looks up the
+		// variable in the config.
+		{
+			Vars: map[string]interface{}{
+				"listmap": map[string]interface{}{
+					"key1": []interface{}{"a", "b"},
+					"key2": []interface{}{"c", "d"},
+				},
+			},
+			Config: map[string]interface{}{
+				"listmap": "${var.listmap}",
+			},
+			Key:   "listmap.key1",
+			Value: nil,
+		},
+	}
+
+	for i, tc := range cases {
+		var rawC *config.RawConfig
+		if tc.Config != nil {
+			var err error
+			rawC, err = config.NewRawConfig(tc.Config)
+			if err != nil {
+				t.Fatalf("err: %s", err)
+			}
+		}
+
+		if tc.Vars != nil {
+			vs := make(map[string]ast.Variable)
+			for k, v := range tc.Vars {
+				hilVar, err := hil.InterfaceToVariable(v)
+				if err != nil {
+					t.Fatalf("%#v to var: %s", v, err)
+				}
+				vs["var."+k] = hilVar
+			}
+			if err := rawC.Interpolate(vs); err != nil {
+				t.Fatalf("err: %s", err)
+			}
+		}
+
+		rc := NewResourceConfig(rawC)
+		rc.interpolateForce()
+
+		// Test getting a key
+		t.Run(fmt.Sprintf("get-%d", i), func(t *testing.T) {
+			v, ok := rc.GetRaw(tc.Key)
+			if ok && v == nil {
+				t.Fatal("(nil, true) returned from GetRaw")
+			}
+
+			if !reflect.DeepEqual(v, tc.Value) {
+				t.Fatalf("%d bad: %#v", i, v)
+			}
+		})
+	}
+}
+
 func TestResourceConfigIsComputed(t *testing.T) {
 	cases := []struct {
 		Name   string