fix: create the cache dir before symlinking the re-warm project at it

benchmarkFixture.js

@@ -406,6 +406,12 @@ export default async function benchmark (pm, fixture, opts) {
         if (err?.code !== 'ENOENT') throw err
       }
     }
+    // The cache dir may not exist right now: it was deleted two rows up, and
+    // a manager whose `node_modules` row is a registry-free no-op (pnpm
+    // restores the tree from the lockfile copy inside it) never recreated
+    // it. A symlink to a path that isn't there is dangling, and the warm-up
+    // install fails trying to mkdir its store through it.
+    await fs.mkdir(path.join(cwd, 'cache'), { recursive: true })
     await fs.symlink(path.join(cwd, 'cache'), path.join(rewarmDir, 'cache'), 'dir')
     measureInstall(pm, rewarmDir, env)
   } finally {

mergeResults.js

@@ -47,7 +47,18 @@ async function main () {
   if (!samplesDir) {
     throw new Error('Usage: node mergeResults.js <dir containing one subdirectory per run>')
   }
-  const runDirs = fs.readdirSync(samplesDir, { withFileTypes: true })
+  // A samples directory that doesn't exist means no measuring job uploaded
+  // anything — every one of them failed. That is the same situation as an
+  // empty directory, and it deserves the same explanation rather than a raw
+  // ENOENT from `readdirSync`.
+  let entries
+  try {
+    entries = fs.readdirSync(samplesDir, { withFileTypes: true })
+  } catch (err) {
+    if (err.code !== 'ENOENT') throw err
+    entries = []
+  }
+  const runDirs = entries
     .filter((entry) => entry.isDirectory())
     // Sorted so that a merge of the same runs always produces the same file,
     // whatever order the artifacts happened to be downloaded in.