[web] isolate cypress webpack caches (#33516)

GitOrigin-RevId: 65f8bf162df4fa3b67c8ac19f36fd578251e88f4

services/web/frontend/macros/cypress-cache-variant.js

@@ -0,0 +1,23 @@
+const path = require('path')
+
+// Returns the cache subdirectory name for the current Cypress CT variant,
+// or null when CYPRESS_RESULTS is not set.
+// Throws if the derived basename is unsafe to prevent path traversal or
+// absolute-path escapes.
+function cypressCacheVariant() {
+  if (!process.env.CYPRESS_RESULTS) return null
+  const variant = path.basename(process.env.CYPRESS_RESULTS)
+  if (
+    !variant ||
+    variant === '.' ||
+    variant === '..' ||
+    path.isAbsolute(variant)
+  ) {
+    throw new Error(
+      `CYPRESS_RESULTS must resolve to a safe basename; got "${process.env.CYPRESS_RESULTS}"`
+    )
+  }
+  return variant
+}
+
+module.exports = cypressCacheVariant

services/web/frontend/macros/invalidate-babel-cache-if-needed.js

@@ -1,9 +1,13 @@
 const fs = require('fs')
 const Path = require('path')
 const Settings = require('@overleaf/settings')
+const cypressCacheVariant = require('./cypress-cache-variant')
 
 module.exports = function invalidateBabelCacheIfNeeded() {
-  const cacheDir = Path.join(__dirname, '../../node_modules/.cache')
+  // Use a unique subdirectory per Cypress CT variant to avoid parallel jobs
+  // racing on the shared babel cache and state file.
+  const suffix = cypressCacheVariant() ?? ''
+  const cacheDir = Path.join(__dirname, '../../node_modules/.cache', suffix)
   const cachePath = Path.join(cacheDir, 'babel-loader')
   const statePath = Path.join(cacheDir, 'last-overleafModuleImports.json')
   let lastState = ''