fix: try not to make network requests with prefer offline (#10334)

.changeset/open-laws-pull.md

@@ -0,0 +1,6 @@
+---
+"@pnpm/npm-resolver": patch
+pnpm: patch
+---
+
+Try to avoid making network calls with preferOffline [#10334](https://github.com/pnpm/pnpm/pull/10334).

resolving/npm-resolver/src/pickPackage.ts

@@ -141,13 +141,14 @@ export async function pickPackage (
     if (ctx.offline === true || ctx.preferOffline === true || opts.pickLowestVersion) {
       metaCachedInStore = await limit(async () => loadMeta(pkgMirror))
 
-      if (ctx.offline) {
+      // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
+      if (ctx.offline || ctx.preferOffline) {
         if (metaCachedInStore != null) return {
           meta: metaCachedInStore,
           pickedPackage: _pickPackageFromMeta(metaCachedInStore),
         }
 
-        throw new PnpmError('NO_OFFLINE_META', `Failed to resolve ${toRaw(spec)} in package mirror ${pkgMirror}`)
+        if (ctx.offline) throw new PnpmError('NO_OFFLINE_META', `Failed to resolve ${toRaw(spec)} in package mirror ${pkgMirror}`)
       }
 
       if (metaCachedInStore != null) {

resolving/npm-resolver/test/index.ts

@@ -761,6 +761,45 @@ test('when prefer offline is used, meta from store is used, where latest might b
   nock.cleanAll()
 })
 
+test('prefer offline does not make network requests when cached metadata exists', async () => {
+  nock(registries.default)
+    .get('/is-positive')
+    .reply(200, isPositiveMeta)
+
+  const cacheDir = temporaryDirectory()
+
+  {
+    const { resolveFromNpm } = createResolveFromNpm({
+      cacheDir,
+      registries,
+    })
+
+    await resolveFromNpm({ alias: 'is-positive', bareSpecifier: '1.0.0' }, {})
+  }
+
+  // Wait for the cache file to be written
+  await retryLoadJsonFile<any>(path.join(cacheDir, ABBREVIATED_META_DIR, 'registry.npmjs.org/is-positive.v8')) // eslint-disable-line @typescript-eslint/no-explicit-any
+
+  // Clear all mocks - if a network request is made, nock will throw an error
+  nock.cleanAll()
+  nock.disableNetConnect()
+
+  {
+    const { resolveFromNpm } = createResolveFromNpm({
+      preferOffline: true,
+      cacheDir,
+      registries,
+    })
+
+    const resolveResult = await resolveFromNpm({ alias: 'is-positive', bareSpecifier: '1.0.0' }, {})
+    expect(resolveResult!.id).toBe('is-positive@1.0.0')
+    expect(resolveResult!.resolution).toStrictEqual({
+      integrity: 'sha512-9cI+DmhNhA8ioT/3EJFnt0s1yehnAECyIOXdT+2uQGzcEEBaj8oNmVWj33+ZjPndMIFRQh8JeJlEu1uv5/J7pQ==',
+      tarball: 'https://registry.npmjs.org/is-positive/-/is-positive-1.0.0.tgz',
+    })
+  }
+})
+
 test('error is thrown when package is not found in the registry', async () => {
   const notExistingPackage = 'foo'