Hide fallback choices after loading

[tvararu]

Fixes #912.

Checklist

• The new code additions passed the tests (npm test).
• The linter ran and found no issues (npm run-script lint).

Description

This preserves the isInvisibleDefault flag by adding it to serialisation and deserialisation.

Add a regression test to ensure it works correctly. I've also tested this manually on an actual story.

When the story runs normally, Story.ProcessChoice copies the runtime ChoicePoint.isInvisibleDefault into each generated Choice:

let choice = new Choice();
choice.targetPath = choicePoint.pathOnChoice;
choice.sourcePath = choicePoint.path.toString();
choice.isInvisibleDefault = choicePoint.isInvisibleDefault; // <-- Flag
choice.threadAtGeneration = this.state.callStack.ForkThread();
choice.tags = tags.reverse(); //C# is a stack
choice.text = (startText + choiceOnlyText).replace(/^[ \t]+|[ \t]+$/g, "");

return choice;

Story.currentChoices filters those with isInvisibleDefault:

get currentChoices() {
  let choices: Choice[] = [];

  if (this._state === null) {
    return throwNullException("this._state");
  }
  for (let c of this._state.currentChoices) {
    if (!c.isInvisibleDefault) { // <-- Filtering out invisible choices
      c.index = choices.length;
      choices.push(c);
    }
  }

  return choices;
}

JsonSerialisation uses WriteChoice to store the game state, but that payload omits isInvisibleDefault:

// No invisible flag anywhere
public static WriteChoice(writer: SimpleJson.Writer, choice: Choice) {
  writer.WriteObjectStart();
  writer.WriteProperty("text", choice.text);
  writer.WriteIntProperty("index", choice.index);
  writer.WriteProperty("originalChoicePath", choice.sourcePath);
  writer.WriteIntProperty("originalThreadIndex", choice.originalThreadIndex);
  writer.WriteProperty("targetPath", choice.pathStringOnChoice);
  this.WriteChoiceTags(writer, choice);
  writer.WriteObjectEnd();
}

On reload, JObjectToChoice reconstructs the choice instances, without the flag:

// No invisible flag anywhere
public static JObjectToChoice(jObj: Record<string, any>) {
  let choice = new Choice();
  choice.text = jObj["text"].toString();
  choice.index = parseInt(jObj["index"]);
  choice.sourcePath = jObj["originalChoicePath"].toString();
  choice.originalThreadIndex = parseInt(jObj["originalThreadIndex"]);
  choice.pathStringOnChoice = jObj["targetPath"].toString();
  choice.tags = this.JArrayToTags(jObj);
  return choice;
}

That hits the same currentChoices method as above, but now it doesn't filter anything out.

[smwhr]

I have reported the issue and linked to this fix over in the inkle/ink repo, since it must be happening in the reference implementation also.

[tvararu]

Thanks @smwhr! I haven’t touched C# in 7 years but I’ll see if I have time to open a PR on the main repo.