serve_deno_cache.ts

serve_deno_cache.ts

import { serve } from "https://deno.land/std@0.83.0/http/server.ts";
import { walk } from "https://deno.land/std@0.83.0/fs/walk.ts";

const PORT = 8001;

interface DenoInfo {
  denoDir: string;
  modulesCache: string;
  typescriptCache: string;
}

const getDenoInfo = async (): Promise<DenoInfo> => {
  const infoProcess = Deno.run({
    cmd: ["deno", "info", "--unstable", "--json"],
    stdout: "piped",
  });
  const textDecoder = new TextDecoder();
  return JSON.parse(textDecoder.decode(await infoProcess.output()));
};

const { modulesCache } = await getDenoInfo();

interface DenoCacheMetadata {
  headers: Record<string, string>;
  url: string;
}

const cacheMetadata = new Map<string, DenoCacheMetadata>();

for await (const entry of walk(modulesCache, { exts: [".metadata.json"] })) {
  try {
    const metadataText = await Deno.readTextFile(entry.path);
    const metadata: DenoCacheMetadata = JSON.parse(metadataText);
    cacheMetadata.set(entry.path.replace(".metadata.json", ""), metadata);
  } catch (err) {
    console.log(`${entry.path}: ${err.message}`);
  }
}

const server = serve({ port: PORT });

console.log(`Serving Deno cache on port ${PORT}`);

for await (const req of server) {
  try {
    let foundMetadata: [string, DenoCacheMetadata] | undefined;

    for (const [cachePath, metadata] of cacheMetadata) {
      if (metadata.url.endsWith(req.url)) {
        foundMetadata = [cachePath, metadata];
        break;
      }
    }

    if (foundMetadata) {
      const [cachePath, cacheMetadata] = foundMetadata;
      const cachedFile = await Deno.readTextFile(cachePath);
      if (cachedFile) {
        console.log(cacheMetadata.url);
        req.respond({
          status: 200,
          body: cachedFile,
          headers: new Headers(cacheMetadata.headers),
        });
      } else {
        throw new Error("No cache entry founda");
      }
    }
  } catch (_) {
    req.respond({ status: 404 });
  }
}

serve_deno_cache

A simple utility that starts an HTTP server to serve Deno's cache directory.

Running

Install with deno install --allow-run --allow-net --allow-read https://gist.githubusercontent.com/LukeChannings/151edca27f4e19f50b10af35edb3bf97/raw/db0b6aed7ee19bac3cb81a1fcdf75e0b35730c99/serve_deno_cache.ts

Run with serve_deno_cache

Or run once with deno run --allow-run --allow-net --allow-read https://gist.githubusercontent.com/LukeChannings/151edca27f4e19f50b10af35edb3bf97/raw/db0b6aed7ee19bac3cb81a1fcdf75e0b35730c99/serve_deno_cache.ts

Using the server

Let's say you've installed a dependency like https://deno.land/std@0.83.0/http/server.ts in one of your projects, you can load the module in a browser by navigating to http://localhost:8001/deno.land/std@0.83.0/http/server.ts when serve_deno_cache is running.

You can manually cache dependencies (including TypeScript types) using deno cache https://cdn.skypack.dev/react@17.0.1?dts (for example).

You can then use them in your browser with <script type="module" src="http://localhost:8001/cdn.skypack.dev/react@17.0.1?dts"></script>, all offline.