[phoerious]

Fixes #13970

The previous TempFile saving method failed under Qt6 on certain remote file systems that don't support hard-linking or O_TMPFILE renames, such as remote SMB shares. Here, QFile::rename() created an unamed Q_TMPFILE, and tried to rename it with linkat(), which failed. Since QFile::rename() does not do file replacements, KeePassXC had to remove the target before moving the new file in place, which could cause to data loss when the rename failed.

This patch changes TempFile to a hybrid approach: The database is first written to a temporary file. The temporary file is committed to disk, and then streamed to a named sibling of the target file. Streaming avoids using QFile::copy() or QFile::rename(), which can trigger the failure. After straming the file back, the target file is replaced atomically (if possible) with the sibling.

Warning

Needs testing. It's quite possible that it fixes the addressed issue, but reintroduces the Dropbox locking issues that the original TempFile saving method was supposed to solve.

Codex created a first rough draft and wrote the tests.

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)

[Copilot]

🟡 Changes recommended

Two active issues remain in src/core/Database.cpp: an unbalanced Windows error message and a source-text change that would invalidate existing translations.

2 open issues

• Close the parenthesis in the Windows error message · New
• Preserve the existing translated backup message · New

What changed in this PR

This pull request reworks KeePassXC’s TempFile database-saving path to stage data in a sibling file, synchronize it, and perform platform-native replacement, improving reliability on remote filesystems.

Changes:

• Added POSIX and Windows file synchronization and replacement helpers.
• Reworked staged saves to preserve the original database on replacement failures and retain recovery copies.
• Updated save-method documentation and removed the obsolete restore helper.
• Added regression coverage for staged saves, atomic saves, permissions, recovery, failures, and cleanup.

Review comments remain regarding an unbalanced Windows error message, translation-string compatibility, long filenames exceeding filesystem limits, and replacement of dangling Windows symlinks.

File	Description
tests/​TestDatabase.h	Declares the new staged-save test cases.
tests/​TestDatabase.cpp	Adds coverage for staged saves, atomic saves, failure preservation, recovery, permissions, and temporary-file cleanup.
src/​core/​Database.h	Updates save-method documentation and removes the obsolete restore helper declaration.
src/​core/​Database.cpp	Implements file synchronization, native replacement, staged sibling writes, recovery handling, and related save-path logic.

_{Review effort: Lite}

[Copilot]

🟡 Changes recommended

A critical test assertion omits “database” from the expected backup-path pattern, so the staged-save recovery check fails at regex matching instead of validating recovery.

1 open issue

• Match the staged-save error’s “Backup database located at” text · New

2 resolved since last review

• Preserve the existing translated backup message
• Close the parenthesis in the Windows error message

_{Review effort: Lite}

[codecov]

Codecov Report

❌ Patch coverage is 69.89247% with 28 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.24%. Comparing base (c263a11) to head (45056dc).

Files with missing lines	Patch %	Lines
src/core/Database.cpp	69.57%	28 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #13992      +/-   ##
===========================================
+ Coverage    61.19%   61.24%   +0.05%     
===========================================
  Files          396      396              
  Lines        37926    37988      +62     
===========================================
+ Hits         23208    23264      +56     
- Misses       14718    14724       +6     

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