125 lines
4.9 KiB
TypeScript
125 lines
4.9 KiB
TypeScript
import { describe, expect, test } from "bun:test";
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import { Tensor } from "@huggingface/transformers";
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import {
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PROMPT_PREFIX_KWARG,
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WHISPER_DECODER_POSITIONS,
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buildPromptPrefix,
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installPromptSupport,
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type PromptableModel,
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} from "../src/worker/prompt";
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const PREV = 50362;
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/**
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* Stand-in for a Transformers.js Whisper model: records the kwargs each
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* generate() call received and, like the real one, returns the decoder input
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* followed by the "generated" tokens as an int64 [1, n] tensor.
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*/
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function fakeModel(initTokens: number[], generated: number[] = [50365, 400, 401, 50400]) {
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const calls: Record<string, unknown>[] = [];
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const model: PromptableModel & { calls: typeof calls } = {
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calls,
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_prepare_generation_config: (_config, kwargs) => ({ fromKwargs: kwargs }),
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_retrieve_init_tokens: () => [...initTokens],
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async generate(kwargs) {
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calls.push(kwargs);
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const input = (kwargs.decoder_input_ids as number[] | undefined) ?? initTokens;
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const sequence = [...input, ...generated];
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return new Tensor("int64", BigInt64Array.from(sequence.map(BigInt)), [1, sequence.length]);
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},
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};
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return model;
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}
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function tokens(output: unknown): number[] {
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return (output as Tensor).tolist()[0]!.map(Number);
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}
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describe("installPromptSupport (D-WS2a)", () => {
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test("without a prompt kwarg, generate is called exactly as before", async () => {
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const model = fakeModel([50258, 50259, 50360]);
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installPromptSupport(model);
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const kwargs = { max_new_tokens: 440, return_timestamps: true };
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const output = await model.generate({ ...kwargs });
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expect(model.calls).toEqual([kwargs]);
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expect(tokens(output)).toEqual([50258, 50259, 50360, 50365, 400, 401, 50400]);
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});
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test("an empty prefix is the same as no prompt", async () => {
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const model = fakeModel([50258]);
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installPromptSupport(model);
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await model.generate({ max_new_tokens: 440, [PROMPT_PREFIX_KWARG]: [] });
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expect(model.calls).toEqual([{ max_new_tokens: 440 }]);
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});
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test("a prefix is prepended to the init tokens and stripped from the output", async () => {
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const model = fakeModel([50258, 50259, 50360]);
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installPromptSupport(model);
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const output = await model.generate({
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max_new_tokens: 440,
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language: "en",
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[PROMPT_PREFIX_KWARG]: [PREV, 1, 2],
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});
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const call = model.calls[0]!;
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expect(call.decoder_input_ids).toEqual([PREV, 1, 2, 50258, 50259, 50360]);
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expect(call).not.toHaveProperty(PROMPT_PREFIX_KWARG);
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expect(call.language).toBe("en");
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// Prompt tokens would otherwise reach _decode_asr as transcript text.
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expect(tokens(output)).toEqual([50258, 50259, 50360, 50365, 400, 401, 50400]);
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});
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test("works for English-only models (init tokens are just <|startoftranscript|>)", async () => {
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const model = fakeModel([50257]);
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installPromptSupport(model);
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const output = await model.generate({ max_new_tokens: 440, [PROMPT_PREFIX_KWARG]: [50361, 7] });
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expect(model.calls[0]!.decoder_input_ids).toEqual([50361, 7, 50257]);
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expect(tokens(output)[0]).toBe(50257);
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});
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test("caps max_new_tokens so prompt + init + new tokens fit Whisper's 448 positions", async () => {
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const model = fakeModel([50258, 50259, 50360]);
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installPromptSupport(model);
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const prefix = [PREV, ...Array.from({ length: 223 }, (_, i) => 1000 + i)];
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await model.generate({ max_new_tokens: 440, [PROMPT_PREFIX_KWARG]: prefix });
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expect(WHISPER_DECODER_POSITIONS).toBe(448);
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expect(model.calls[0]!.max_new_tokens).toBe(448 - 227);
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// A short prompt keeps the D-021 value.
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await model.generate({ max_new_tokens: 440, [PROMPT_PREFIX_KWARG]: [PREV, 5] });
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expect(model.calls[1]!.max_new_tokens).toBe(440);
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});
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test("installing twice wraps once", async () => {
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const model = fakeModel([50258]);
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installPromptSupport(model);
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installPromptSupport(model);
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await model.generate({ max_new_tokens: 440, [PROMPT_PREFIX_KWARG]: [PREV, 5] });
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expect(model.calls).toHaveLength(1);
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expect(model.calls[0]!.decoder_input_ids).toEqual([PREV, 5, 50258]);
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});
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});
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describe("buildPromptPrefix", () => {
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const tokenizer = {
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encode: (text: string, _options: { add_special_tokens: false }) =>
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[...text].map((c) => c.charCodeAt(0)),
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convert_tokens_to_ids: (token: string) => (token === "<|startofprev|>" ? PREV : -1),
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};
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test("no hint → no prefix", () => {
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expect(buildPromptPrefix(tokenizer, "")).toEqual([]);
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expect(buildPromptPrefix(tokenizer, " \n ")).toEqual([]);
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});
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test("a hint → <|startofprev|> then the space-led, full-stopped hint tokens", () => {
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expect(buildPromptPrefix(tokenizer, "Max\nVoid")).toEqual([
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PREV,
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...[..." Max, Void."].map((c) => c.charCodeAt(0)),
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]);
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});
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test("a huge hint stays within the 120-token budget (D-WS2a)", () => {
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const prefix = buildPromptPrefix(tokenizer, "Maxwell, ".repeat(500));
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expect(prefix.length).toBeLessThanOrEqual(121);
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});
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});
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