fix(vitest): add more type guards for --merge-reports

packages/vitest/src/node/reporters/blob.ts

@@ -1,4 +1,4 @@
-import { mkdir, readFile, readdir, writeFile } from 'node:fs/promises'
+import { mkdir, readFile, readdir, stat, writeFile } from 'node:fs/promises'
 import { existsSync } from 'node:fs'
 import { parse, stringify } from 'flatted'
 import { dirname, resolve } from 'pathe'
@@ -80,10 +80,22 @@ export async function readBlobs(
   const resolvedDir = resolve(process.cwd(), blobsDirectory)
   const blobsFiles = await readdir(resolvedDir)
   const promises = blobsFiles.map(async (file) => {
-    const content = await readFile(resolve(resolvedDir, file), 'utf-8')
+    const fullPath = resolve(resolvedDir, file)
+    const stats = await stat(fullPath)
+    if (!stats.isFile()) {
+      throw new TypeError(
+        `vitest.mergeReports() expects all paths in "${blobsDirectory}" to be files generated by the blob reporter, but "${file}" is not a file`,
+      )
+    }
+    const content = await readFile(fullPath, 'utf-8')
     const [version, files, errors, moduleKeys, coverage] = parse(
       content,
     ) as MergeReport
+    if (!version) {
+      throw new TypeError(
+        `vitest.mergeReports() expects all paths in "${blobsDirectory}" to be files generated by the blob reporter, but "${file}" is not a valid blob file`,
+      )
+    }
     return { version, files, errors, moduleKeys, coverage }
   })
   const blobs = await Promise.all(promises)
@@ -94,6 +106,13 @@ export async function readBlobs(
     )
   }
 
+  const versions = new Set(blobs.map(blob => blob.version))
+  if (versions.size > 1) {
+    throw new Error(
+      `vitest.mergeReports() requires all blob files to be generated by the same Vitest version, received ${Array.from(versions).join(', ')}`,
+    )
+  }
+
   // fake module graph - it is used to check if module is imported, but we don't use values inside
   const projects = Object.fromEntries(
     projectsArray.map(p => [p.getName(), p]),