feat(document_loaders): add SupadataLoader

[MUDASSIR-75]

Description

This PR adds a new SupadataLoader to @langchain/community’s document loaders.

The loader is a thin wrapper around the official @supadata/js SDK and supports two Supadata operations:

• transcript – fetches text transcripts for a URL (e.g. YouTube).
• metadata – fetches structured metadata for a URL (YouTube via youtube.video, other URLs via web.scrape).

Implementation details:

• Loader lives at: libs/langchain-community/src/document_loaders/web/supadata.ts.
• Exposes a typed SupadataLoaderParams interface with:
  • urls (required array of URLs),
  • operation ("transcript" | "metadata", default "transcript"),
  • lang, text, mode,
  • params for arbitrary extra Supadata options.
• API key resolution:
  • Uses the apiKey constructor param when provided.
  • Fallback to the SUPADATA_API_KEY environment variable via getEnvironmentVariable.
• Returns LangChain Document instances with:
  • metadata.source set to the URL,
  • metadata.supadataOperation set to "transcript", "transcript_job", or "metadata",
  • for transcripts, pageContent is the transcript text (or a message indicating an async job with jobId).

Usage

import { SupadataLoader } from "@langchain/community/document_loaders/web/supadata";

const loader = new SupadataLoader({
  urls: ["https://www.youtube.com/watch?v=dQw4w9WgXcQ"],
  operation: "transcript",
  apiKey: process.env.SUPADATA_API_KEY,
  lang: "en",
  text: true,
  mode: "auto",
});

const docs = await loader.load();
console.log(docs[0].pageContent);

Metadata example:

const loader = new SupadataLoader({
  urls: ["https://www.youtube.com/watch?v=dQw4w9WgXcQ"],
  operation: "metadata",
  apiKey: process.env.SUPADATA_API_KEY,
});

const [doc] = await loader.load();
console.log(doc.metadata.supadataOperation); // "metadata"
console.log(doc.pageContent); // JSON string with Supadata metadata

Tests

From libs/langchain-community:

pnpm test -- supadata

This runs src/document_loaders/tests/supadata.test.ts, which:

• Mocks @supadata/js and verifies the Supadata client is constructed with the correct apiKey.
• Asserts that transcript responses are converted into Document objects with the expected pageContent.
• Asserts that metadata responses are converted into Document objects with the expected pageContent and metadata.supadataOperation.

All tests are currently passing.

Issue

N/A – new integration.

Dependencies

• Adds @supadata/js as a dev dependency for @langchain/community to support unit tests.
• The loader dynamically imports @supadata/js at runtime (await import("@supadata/js")), so users must install @supadata/js in their own project to use this loader.

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[MUDASSIR-75]

Hi @hntrl, could you please help approve the workflows for this PR? Thank you!