terraform: clean up any final TODOs with comments and placeholders

terraform/shadow_context.go

@@ -48,9 +48,15 @@ func newShadowContext(c *Context) (*Context, *Context, Shadow) {
 		module:     c.module,
 		state:      c.state.DeepCopy(),
 		targets:    targetRaw.([]string),
-		uiInput:    nil, // TODO
 		variables:  varRaw.(map[string]interface{}),
 
+		// NOTE(mitchellh): This is not going to work for shadows that are
+		// testing that input results in the proper end state. At the time
+		// of writing, input is not used in any state-changing graph
+		// walks anyways, so this checks nothing. We set it to this to avoid
+		// any panics but even a "nil" value worked here.
+		uiInput: new(MockUIInput),
+
 		// Hardcoded to 4 since parallelism in the shadow doesn't matter
 		// a ton since we're doing far less compared to the real side
 		// and our operations are MUCH faster.

terraform/shadow_resource_provider.go

@@ -738,14 +738,8 @@ func (p *shadowResourceProviderShadow) ReadDataApply(
 	return result.Result, result.ResultErr
 }
 
-// TODO
-// TODO
-// TODO
-// TODO
-// TODO
-
 func (p *shadowResourceProviderShadow) ImportState(info *InstanceInfo, id string) ([]*InstanceState, error) {
-	return nil, nil
+	panic("import not supported by shadow graph")
 }
 
 // The structs for the various function calls are put below. These structs