From 0ac092d1772f6c06e802d6eddec3a5e5b948f252 Mon Sep 17 00:00:00 2001
From: Andrey Antukh <niwi@niwi.nz>
Date: Wed, 10 Jun 2026 10:58:50 +0200
Subject: [PATCH] :bug: Make set-file-shared idempotent to fix race condition
 with optimistic updates (#10093)

---
 backend/src/app/rpc/commands/files.clj       |  6 +++
 backend/test/backend_tests/rpc_file_test.clj | 43 ++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/backend/src/app/rpc/commands/files.clj b/backend/src/app/rpc/commands/files.clj
index a05ef28e78..e8a4bc32b0 100644
--- a/backend/src/app/rpc/commands/files.clj
+++ b/backend/src/app/rpc/commands/files.clj
@@ -974,6 +974,12 @@
                              {:id id})
                  file)
 
+               (= (:is-shared file) (:is-shared params))
+               ;; File is already in the desired state (idempotent);
+               ;; this can happen when the frontend sends a duplicate
+               ;; request due to optimistic updates or race conditions.
+               file
+
                :else
                (ex/raise :type :validation
                          :code :invalid-shared-state
diff --git a/backend/test/backend_tests/rpc_file_test.clj b/backend/test/backend_tests/rpc_file_test.clj
index 24bb45cb80..5460b4143f 100644
--- a/backend/test/backend_tests/rpc_file_test.clj
+++ b/backend/test/backend_tests/rpc_file_test.clj
@@ -830,6 +830,49 @@
     (t/is (th/ex-info? error))
     (t/is (th/ex-of-type? error :not-found))))
 
+(t/deftest set-file-shared-idempotent
+  (let [profile (th/create-profile* 1)
+        file    (th/create-file* 1 {:project-id (:default-project-id profile)
+                                    :profile-id (:id profile)})]
+
+    ;; Share the file
+    (let [data {::th/type :set-file-shared
+                ::rpc/profile-id (:id profile)
+                :id (:id file)
+                :is-shared true}
+          out  (th/command! data)]
+      (t/is (nil? (:error out)))
+      (t/is (true? (-> out :result :is-shared))))
+
+    ;; Calling set-file-shared with is-shared=true again should be a
+    ;; no-op success (idempotent), not an error.
+    (let [data {::th/type :set-file-shared
+                ::rpc/profile-id (:id profile)
+                :id (:id file)
+                :is-shared true}
+          out  (th/command! data)]
+      (t/is (nil? (:error out)))
+      (t/is (true? (-> out :result :is-shared))))
+
+    ;; Unshare the file
+    (let [data {::th/type :set-file-shared
+                ::rpc/profile-id (:id profile)
+                :id (:id file)
+                :is-shared false}
+          out  (th/command! data)]
+      (t/is (nil? (:error out)))
+      (t/is (false? (-> out :result :is-shared))))
+
+    ;; Calling set-file-shared with is-shared=false again should also
+    ;; be a no-op success (idempotent).
+    (let [data {::th/type :set-file-shared
+                ::rpc/profile-id (:id profile)
+                :id (:id file)
+                :is-shared false}
+          out  (th/command! data)]
+      (t/is (nil? (:error out)))
+      (t/is (false? (-> out :result :is-shared))))))
+
 (t/deftest permissions-checks-link-to-library-1
   (let [profile1 (th/create-profile* 1)
         profile2 (th/create-profile* 2)