feat: add built-in caching via inputs (#89)

src/cache.ts

@@ -0,0 +1,81 @@
+import process from "node:process";
+import cache from "@actions/cache";
+import core from "@actions/core";
+
+const state = {
+  DENO_DIR: "DENO_DIR",
+  CACHE_HIT: "CACHE_HIT",
+  CACHE_SAVE: "CACHE_SAVE",
+} as const;
+
+export async function saveCache() {
+  if (!cache.isFeatureAvailable()) {
+    core.warning("Caching is not available. Caching is skipped.");
+    return;
+  }
+
+  const denoDir = core.getState(state.DENO_DIR);
+  const saveKey = core.getState(state.CACHE_SAVE);
+  if (!denoDir || !saveKey) {
+    core.info("Caching is not enabled. Caching is skipped.");
+    return;
+  } else if (core.getState(state.CACHE_HIT) === "true") {
+    core.info(
+      `Cache hit occurred on the primary key "${saveKey}", not saving cache.`,
+    );
+    return;
+  }
+
+  await cache.saveCache([denoDir], saveKey);
+  core.info(`Cache saved with key: "${saveKey}".`);
+}
+
+export async function restoreCache(cacheHash: string) {
+  try {
+    const denoDir = await resolveDenoDir();
+    core.saveState(state.DENO_DIR, denoDir);
+
+    const { GITHUB_JOB, RUNNER_OS, RUNNER_ARCH } = process.env;
+    const restoreKey = `deno-cache-${RUNNER_OS}-${RUNNER_ARCH}`;
+    // CI jobs often download different dependencies, so include Job ID in the cache key.
+    const primaryKey = `${restoreKey}-${GITHUB_JOB}-${cacheHash}`;
+    core.saveState(state.CACHE_SAVE, primaryKey);
+
+    const loadedCacheKey = await cache.restoreCache([denoDir], primaryKey, [
+      restoreKey,
+    ]);
+    const cacheHit = primaryKey === loadedCacheKey;
+    core.setOutput("cache-hit", cacheHit);
+    core.saveState(state.CACHE_HIT, cacheHit);
+
+    const message = loadedCacheKey
+      ? `Cache key used: "${loadedCacheKey}".`
+      : `No cache found for restore key: "${restoreKey}".`;
+    core.info(message);
+  } catch (err) {
+    core.warning(
+      new Error("Failed to restore cache. Continuing without cache.", {
+        cause: err,
+      }),
+    );
+  }
+}
+
+async function resolveDenoDir(): Promise<string> {
+  const { DENO_DIR } = process.env;
+  if (DENO_DIR) return DENO_DIR;
+
+  // Retrieve the DENO_DIR from `deno info --json`
+  const { exec } = await import("node:child_process");
+  const output = await new Promise<string>((res, rej) => {
+    exec("deno info --json", (err, stdout) => err ? rej(err) : res(stdout));
+  });
+  const info = JSON.parse(output);
+  if (typeof info.denoDir !== "string") {
+    throw new Error(
+      "`deno info --json` output did not contain a denoDir property. " +
+        "Maybe try updating this action or your Deno version if either are old.",
+    );
+  }
+  return info.denoDir;
+}