overleaf/server-ce/hotfix/5.5.3/pr_27230.patch

diff --git a/services/web/app.mjs b/services/web/app.mjs
index b7c723da3d77..3f54cc36a8c3 100644
--- a/services/web/app.mjs
+++ b/services/web/app.mjs
@@ -56,14 +56,8 @@ if (Settings.catchErrors) {
 // Create ./data/dumpFolder if needed
 FileWriter.ensureDumpFolderExists()

-if (
-  !Features.hasFeature('project-history-blobs') &&
-  !Features.hasFeature('filestore')
-) {
-  throw new Error(
-    'invalid config: must enable either project-history-blobs (Settings.enableProjectHistoryBlobs=true) or enable filestore (Settings.disableFilestore=false)'
-  )
-}
+// Validate combination of feature flags.
+Features.validateSettings()

 // handle SIGTERM for graceful shutdown in kubernetes
 process.on('SIGTERM', function (signal) {
diff --git a/services/web/app/src/Features/History/HistoryURLHelper.js b/services/web/app/src/Features/History/HistoryURLHelper.js
index 8b8d8cbdd730..acb43ced68e0 100644
--- a/services/web/app/src/Features/History/HistoryURLHelper.js
+++ b/services/web/app/src/Features/History/HistoryURLHelper.js
@@ -8,7 +8,7 @@ function projectHistoryURLWithFilestoreFallback(
 ) {
   const filestoreURL = `${Settings.apis.filestore.url}/project/${projectId}/file/${fileRef._id}?from=${origin}`
   // TODO: When this file is converted to ES modules we will be able to use Features.hasFeature('project-history-blobs'). Currently we can't stub the feature return value in tests.
-  if (fileRef.hash && Settings.enableProjectHistoryBlobs) {
+  if (fileRef.hash && Settings.filestoreMigrationLevel >= 1) {
     return {
       url: `${Settings.apis.project_history.url}/project/${historyId}/blob/${fileRef.hash}`,
       fallbackURL: filestoreURL,
diff --git a/services/web/app/src/infrastructure/Features.js b/services/web/app/src/infrastructure/Features.js
index aaf51103b9b8..89c8e6b841d0 100644
--- a/services/web/app/src/infrastructure/Features.js
+++ b/services/web/app/src/infrastructure/Features.js
@@ -19,8 +19,7 @@ const trackChangesModuleAvailable =
  * @property {boolean | undefined} enableGithubSync
  * @property {boolean | undefined} enableGitBridge
  * @property {boolean | undefined} enableHomepage
- * @property {boolean | undefined} enableProjectHistoryBlobs
- * @property {boolean | undefined} disableFilestore
+ * @property {number} filestoreMigrationLevel
  * @property {boolean | undefined} enableSaml
  * @property {boolean | undefined} ldap
  * @property {boolean | undefined} oauth
@@ -29,7 +28,39 @@ const trackChangesModuleAvailable =
  * @property {boolean | undefined} saml
  */

+/**
+ * @return {{'project-history-blobs': boolean, filestore: boolean}}
+ */
+function getFilestoreMigrationOptions() {
+  switch (Settings.filestoreMigrationLevel) {
+    case 0:
+      return {
+        'project-history-blobs': false,
+        filestore: true,
+      }
+    case 1:
+      return {
+        'project-history-blobs': true,
+        filestore: true,
+      }
+
+    case 2:
+      return {
+        'project-history-blobs': true,
+        filestore: false,
+      }
+    default:
+      throw new Error(
+        `invalid OVERLEAF_FILESTORE_MIGRATION_LEVEL=${Settings.filestoreMigrationLevel}, expected 0, 1 or 2`
+      )
+  }
+}
+
 const Features = {
+  validateSettings() {
+    getFilestoreMigrationOptions() // throws for invalid settings
+  },
+
   /**
    * @returns {boolean}
    */
@@ -89,9 +120,9 @@ const Features = {
             Settings.enabledLinkedFileTypes.includes('url')
         )
       case 'project-history-blobs':
-        return Boolean(Settings.enableProjectHistoryBlobs)
+        return getFilestoreMigrationOptions()['project-history-blobs']
       case 'filestore':
-        return Boolean(Settings.disableFilestore) === false
+        return getFilestoreMigrationOptions().filestore
       case 'support':
         return supportModuleAvailable
       case 'symbol-palette':
diff --git a/services/web/config/settings.defaults.js b/services/web/config/settings.defaults.js
index bd0730d5d00c..4df63ebd7c6c 100644
--- a/services/web/config/settings.defaults.js
+++ b/services/web/config/settings.defaults.js
@@ -440,6 +440,9 @@ module.exports = {
     ','
   ),

+  filestoreMigrationLevel:
+    parseInt(process.env.OVERLEAF_FILESTORE_MIGRATION_LEVEL, 10) || 0,
+
   // i18n
   // ------
   //

diff --git a/services/history-v1/storage/scripts/back_fill_file_hash.mjs b/services/history-v1/storage/scripts/back_fill_file_hash.mjs
index 0ccadaf5a955..2e12328e5c49 100644
--- a/services/history-v1/storage/scripts/back_fill_file_hash.mjs
+++ b/services/history-v1/storage/scripts/back_fill_file_hash.mjs
@@ -150,10 +150,6 @@ const CONCURRENT_BATCHES = parseInt(process.env.CONCURRENT_BATCHES || '2', 10)
 const RETRIES = parseInt(process.env.RETRIES || '10', 10)
 const RETRY_DELAY_MS = parseInt(process.env.RETRY_DELAY_MS || '100', 10)

-const USER_FILES_BUCKET_NAME = process.env.USER_FILES_BUCKET_NAME || ''
-if (!USER_FILES_BUCKET_NAME) {
-  throw new Error('env var USER_FILES_BUCKET_NAME is missing')
-}
 const RETRY_FILESTORE_404 = process.env.RETRY_FILESTORE_404 === 'true'
 const BUFFER_DIR = fs.mkdtempSync(
   process.env.BUFFER_DIR_PREFIX || '/tmp/back_fill_file_hash-'

diff --git a/services/web/app/src/infrastructure/Features.js b/services/web/app/src/infrastructure/Features.js
index 89c8e6b841d0..6147e70e0faf 100644
--- a/services/web/app/src/infrastructure/Features.js
+++ b/services/web/app/src/infrastructure/Features.js
@@ -28,37 +28,13 @@ const trackChangesModuleAvailable =
  * @property {boolean | undefined} saml
  */

-/**
- * @return {{'project-history-blobs': boolean, filestore: boolean}}
- */
-function getFilestoreMigrationOptions() {
-  switch (Settings.filestoreMigrationLevel) {
-    case 0:
-      return {
-        'project-history-blobs': false,
-        filestore: true,
-      }
-    case 1:
-      return {
-        'project-history-blobs': true,
-        filestore: true,
-      }
-
-    case 2:
-      return {
-        'project-history-blobs': true,
-        filestore: false,
-      }
-    default:
+const Features = {
+  validateSettings() {
+    if (![0, 1, 2].includes(Settings.filestoreMigrationLevel)) {
       throw new Error(
         `invalid OVERLEAF_FILESTORE_MIGRATION_LEVEL=${Settings.filestoreMigrationLevel}, expected 0, 1 or 2`
       )
-  }
-}
-
-const Features = {
-  validateSettings() {
-    getFilestoreMigrationOptions() // throws for invalid settings
+    }
   },

   /**
@@ -120,9 +96,9 @@ const Features = {
             Settings.enabledLinkedFileTypes.includes('url')
         )
       case 'project-history-blobs':
-        return getFilestoreMigrationOptions()['project-history-blobs']
+        return Settings.filestoreMigrationLevel > 0
       case 'filestore':
-        return getFilestoreMigrationOptions().filestore
+        return Settings.filestoreMigrationLevel < 2
       case 'support':
         return supportModuleAvailable
       case 'symbol-palette':