Prompt with nested variables

[zirkelc]

Hey,

I would like to know if you're in adding support for nested prompt variables:

  const prompt = PromptTemplate.fromTemplate<{
    simple: string;
    nested: { a: string; b: string };
  }>(`
  Simple: {simple}
  Nested:
    A: {nested.a}
    B: {nested.b}`);

  const formatted = await prompt.format({
    simple: 'simple',
    nested: { a: '1', b: '2' },
  });

console.log(formatted);
// Simple: simple
// Nested:
//  - A
//  - B

I know this is easily possible with a RunnableMap before the PromptTemplate via a RunnableSequence. However, I think that creates unnecessary overhead and latency (due to the RunnableMap) and adds more complexity.

The implementation could be done like this:

• extract placeholder name, e.g.{nested.a}
• get value from input["nested.a"] (existing logic)
  • if value is undefined, get value from Lodash.get("nested.a", input) (new logic)
• replace placeholder with value

Let me know what you think.

[ericwooley]

Would love to see this happen, just ran into this.