[stable-34.0] Detect upload conflicts with an If-Match precondition#10394
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Content uploads on the modify path were unconditional PUTs: the extension
never told the server "only accept this if your copy is still the version I
edited." When the server copy changed since the last sync — another device or
user, or an app such as Adobe InDesign/Illustrator issuing rapid multi-step
re-saves — the client silently overwrote it (last-writer-wins, data loss).
Send the base version's etag as an `If-Match` precondition so the server
rejects a conflicting write with 412 Precondition Failed instead of clobbering.
`modifyContents` now takes `baseVersion` + `options` (threaded from the
`modify` call site) and derives the base etag from `baseVersion.contentVersion`
(falling back to the stored metadata etag).
Behaviour is tiered by OS, because Apple's real conflict-resolution contract —
`NSFileProviderModifyItemFailOnConflict` and the
`.localVersionConflictingWithServer` error — is macOS 26.0+ only, while the
extension deploys back to macOS 13:
* macOS 26+ with the system's `.failOnConflict` option: on 412 return
`.localVersionConflictingWithServer` so the system creates a conflict copy
and both versions survive. Advertised via
`NSExtensionFileProviderSupportsFailingUploadOnConflict` in Info.plist.
* macOS 13–25 (best-effort heuristic): always send `If-Match`; on 412 clear
any lock token, signal a working-set re-enumeration, and return a transient
NSCocoaError so the system re-fetches the server version before re-driving
the edit — turning a silent overwrite into a visible sync round-trip.
* macOS 26+ without `.failOnConflict`: unchanged (no `If-Match` sent).
A `sentIfMatch` guard (we only send `If-Match` when a base etag exists) gates
the new 412-as-conflict branch, so a lock-only 412 keeps its previous
stale-lock meaning.
Scope: the single-PUT modify path. Chunked (large-file) uploads need an
upstream NextcloudKit change (an `If-Match` scoped to the assembly MOVE only,
so it does not ride on the chunk PUTs) and are a deferred follow-up.
Tests: added coverage for the precondition being sent, the macOS 26+ conflict
return, and the macOS < 26 transient-retry path; updated the existing 412
lock-token test for the new OS-dependent behaviour; added a
`lastUploadIfMatchHeader` capture knob to the mock remote interface.
Signed-off-by: Iva Horn <iva.horn@nextcloud.com>
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claucambra,
mgallien and
nilsding
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July 17, 2026 14:07
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added
bug
os: 🍎 macOS
claucambra
approved these changes
Jul 17, 2026
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Artifact containing the AppImage: nextcloud-appimage-pr-10394.zip Digest: To test this change/fix you can download the above artifact file, unzip it, and run it. Please make sure to quit your existing Nextcloud app and backup your data. |
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Backport of PR #10393