Adds onCallGenkit

[inlined]

Adds support for a callable function specialization just for Genkit!

This design chooses to implement callable functions by locally redefining necessary interfaces to avoid a dependency on Genkit that is otherwise only needed for type definitions. Once RC.4 is released (fixing compiler errors in firebase-functions when taking a dependency on genkit) we can add genkit as a dev dependency and add a "succeeds if compiles" test to detect changes in the Genkit API.

[inlined]

Tested manually, though it requires a CLI with firebase/firebase-tools#8127

Code:

import { defineSecret } from 'firebase-functions/params';
import { onCallGenkit } from "firebase-functions/https";
import { gemini15Flash, googleAI } from "@genkit-ai/googleai";
import { genkit, z } from "genkit";

const apiKey = defineSecret("GOOGLE_GENAI_API_KEY")

const ai = genkit({
  plugins: [ googleAI(), ],
  model: gemini15Flash,
});

export const jokeTeller = ai.defineFlow({
   name: "jokeTeller",
   inputSchema: z.string().nullable(),
   outputSchema: z.string(),
   streamSchema: z.string(),
}, async (type, { sendChunk }) => {
   const { stream, response } = ai.generateStream(`Tell me a ${type ?? "dad"} joke.`);
   for await (const chunk of stream) {
      sendChunk(chunk.text);
   }
   return (await response).text;
});

export const tellJoke = onCallGenkit({ secrets: [apiKey] }, jokeTeller);

Tests:

❯ curl -X POST -H "Content-Type: application/json" -d '{"data": "software"}' https://us-central1-inlined-junkdrawer.cloudfunctions.net/tellJoke
{"result":"Why do programmers prefer dark mode?\n\nBecause light attracts bugs!\n"}%   

❯ curl -X POST -H "Content-Type: application/json" -H "Accept: text/event-stream" -d '{"data": "software"}' https://us-central1-inlined-junkdrawer.cloudfunctions.net/tellJoke
data: {"message":"Why"}
data: {"message":" do programmers prefer dark mode?\n\nBecause light attracts bugs!\n"}
data: {"result":"Why do programmers prefer dark mode?\n\nBecause light attracts bugs!\n"}

Additionally tested that a second test without using onCallGenkit was able to compile successfully without taking a dependency on Genkit.

[taeold]

This looks awesome!

[taeold]

q: is this visible during firebase deploy?

[inlined]

Only if you do --debug I think. Can figure out for sure later, but I have to run and want to let you cut a release so I can build upon it over the weekend.

[inlined]

Alternatively, we could push this into the CLI where it notices a genkit onCall with no secrets?