feat: allow getting cache key if lock file does not exist

src/cache.test.ts

@@ -54,14 +54,14 @@ describe("Getting the cache key", () => {
     );
   });
 
-  it("should not get the cache key if there is no lock file", async () => {
+  it("should get the cache key if there is no lock file", async () => {
     const { getCacheKey } = await import("./cache.js");
 
     mock.fs.existsSync.mockReturnValue(false);
 
     const cacheKey = await getCacheKey();
 
-    expect(cacheKey).toBeUndefined();
+    expect(cacheKey).toBe(`yarn-install-action-${os.type()}-1.2.3`);
   });
 });
 

src/cache.ts

@@ -4,18 +4,22 @@ import fs from "node:fs";
 import os from "node:os";
 import { getYarnConfig, getYarnVersion } from "./yarn.js";
 
-export async function getCacheKey(): Promise<string | undefined> {
+export async function getCacheKey(): Promise<string> {
   core.info("Getting Yarn version...");
   const version = await getYarnVersion();
 
   core.info("Calculating lock file hash...");
-  if (!fs.existsSync("yarn.lock")) {
-    core.warning(`Lock file not found, skipping cache`);
-    return undefined;
+  let lockFileHash: string | undefined = undefined;
+  if (fs.existsSync("yarn.lock")) {
+    lockFileHash = await hashFile("yarn.lock", { algorithm: "md5" });
+  } else {
+    core.warning(`Lock file could not be found, using empty hash`);
   }
-  const lockFileHash = await hashFile("yarn.lock", { algorithm: "md5" });
 
-  const cacheKey = `yarn-install-action-${os.type()}-${version}-${lockFileHash}`;
+  let cacheKey = `yarn-install-action-${os.type()}-${version}`;
+  if (lockFileHash !== undefined) {
+    cacheKey += `-${lockFileHash}`;
+  }
   core.info(`Using cache key: ${cacheKey}`);
 
   return cacheKey;

src/index.ts

@@ -9,37 +9,29 @@ async function main(): Promise<void> {
   });
 
   const cacheKey = await core.group("Getting cache key", getCacheKey);
+  const cachePaths = await core.group("Getting cache paths", getCachePaths);
 
-  let cachePaths: string[] = [];
-  if (cacheKey !== undefined) {
-    cachePaths = await core.group("Getting cache paths", getCachePaths);
-  }
-
-  if (cacheKey !== undefined) {
-    const cacheFound = await core.group("Restoring cache", async () => {
-      const cacheId = await cache.restoreCache(cachePaths.slice(), cacheKey);
-      if (cacheId === undefined) {
-        core.warning("Cache not found");
-        return false;
-      }
-      return true;
-    });
-
-    if (cacheFound) {
-      core.info("Cache restored successfully");
-      return;
+  const cacheFound = await core.group("Restoring cache", async () => {
+    const cacheId = await cache.restoreCache(cachePaths.slice(), cacheKey);
+    if (cacheId === undefined) {
+      core.warning("Cache not found");
+      return false;
     }
+    return true;
+  });
+
+  if (cacheFound) {
+    core.info("Cache restored successfully");
+    return;
   }
 
   await core.group("Installing dependencies", async () => {
     return yarnInstall();
   });
 
-  if (cacheKey !== undefined) {
-    await core.group("Saving cache", async () => {
-      return cache.saveCache(cachePaths.slice(), cacheKey);
-    });
-  }
+  await core.group("Saving cache", async () => {
+    return cache.saveCache(cachePaths.slice(), cacheKey);
+  });
 }
 
 main().catch((err) => core.setFailed(err));