feat: Check for existing bun before downloading (#138)

* feat: Check for existing bun before downloading

Check for existing bun with same version number, if it exists we skip any futher actions. This avoids downloading cache or bun over the network.

* [autofix.ci] apply automated fixes

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/action.ts

@@ -7,6 +7,7 @@ import {
   symlinkSync,
   renameSync,
   copyFileSync,
+  existsSync,
 } from "node:fs";
 import { addPath, info, warning } from "@actions/core";
 import { isFeatureAvailable, restoreCache } from "@actions/cache";
@@ -73,27 +74,40 @@ export default async (options: Input): Promise<Output> => {
 
   let revision: string | undefined;
   let cacheHit = false;
-  if (cacheEnabled) {
-    const cacheKey = createHash("sha1").update(url).digest("base64");
 
-    const cacheRestored = await restoreCache([bunPath], cacheKey);
+  // Check if Bun executable already exists and matches requested version
-    if (cacheRestored) {
+  if (!options.customUrl && existsSync(bunPath)) {
-      revision = await getRevision(bunPath);
+    const existingRevision = await getRevision(bunPath);
-      if (revision) {
+    if (existingRevision && isVersionMatch(existingRevision, options.version)) {
-        cacheHit = true;
+      revision = existingRevision;
-        info(`Using a cached version of Bun: ${revision}`);
+      cacheHit = true; // Treat as cache hit to avoid unnecessary network requests
-      } else {
+      info(`Using existing Bun installation: ${revision}`);
-        warning(
-          `Found a cached version of Bun: ${revision} (but it appears to be corrupted?)`,
-        );
-      }
     }
   }
 
-  if (!cacheHit) {
+  if (!revision) {
-    info(`Downloading a new version of Bun: ${url}`);
+    if (cacheEnabled) {
-    // TODO: remove this, temporary fix for https://github.com/oven-sh/setup-bun/issues/73
+      const cacheKey = createHash("sha1").update(url).digest("base64");
-    revision = await retry(async () => await downloadBun(url, bunPath), 3);
+
+      const cacheRestored = await restoreCache([bunPath], cacheKey);
+      if (cacheRestored) {
+        revision = await getRevision(bunPath);
+        if (revision) {
+          cacheHit = true;
+          info(`Using a cached version of Bun: ${revision}`);
+        } else {
+          warning(
+            `Found a cached version of Bun: ${revision} (but it appears to be corrupted?)`,
+          );
+        }
+      }
+    }
+
+    if (!cacheHit) {
+      info(`Downloading a new version of Bun: ${url}`);
+      // TODO: remove this, temporary fix for https://github.com/oven-sh/setup-bun/issues/73
+      revision = await retry(async () => await downloadBun(url, bunPath), 3);
+    }
   }
 
   if (!revision) {
@@ -122,6 +136,29 @@ export default async (options: Input): Promise<Output> => {
   };
 };
 
+function isVersionMatch(
+  existingRevision: string,
+  requestedVersion?: string,
+): boolean {
+  // If no version specified, default is "latest" - don't match existing
+  if (!requestedVersion) {
+    return false;
+  }
+
+  // Non-pinned versions should never match existing installations
+  if (/^(latest|canary|action)$/i.test(requestedVersion)) {
+    return false;
+  }
+
+  const [existingVersion] = existingRevision.split("+");
+
+  const normalizeVersion = (v: string) => v.replace(/^v/i, "");
+
+  return (
+    normalizeVersion(existingVersion) === normalizeVersion(requestedVersion)
+  );
+}
+
 async function downloadBun(
   url: string,
   bunPath: string,