IsFileWriteable: probe via permission bits, not append-open#20
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The previous implementation tested writability by opening the file with ios_base::app|out, which: 1. As a side effect, created empty files when probing non-existent paths (relevant on platforms where ScanFiles might pass through transient candidate paths). 2. On iOS keyboard extensions, where the data bundle is read-only and sandboxed, generated a 'file-write-data' sandbox deny for every bundled file scanned (colour XMLs, alphabet XMLs, etc.). Each deny produced a kernel log line and forced the kernel to set up + tear down a denied file descriptor. Replace the open-with-append with std::filesystem::status(), checking the permission bits for any write bit (owner/group/others). This is: - Side-effect free: never creates files. - Faster: one stat() per file instead of open()+close(). - Sandbox-clean: no write attempts against read-only paths. Semantically equivalent for all callers (ScanFiles only invokes IsFileWriteable on paths that already exist as regular files, so the 'non-existent file' case doesn't apply in practice). Signed-off-by: will wade <willwade@gmail.com>
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Why
IsFileWriteable()tested writability by opening the file withios_base::app | out. Two problems with that:.appexcontainer. EveryScanFiles()call probed each scanned file with an append-open, producing aSandbox: deny file-write-datalog line per file from the kernel. Several dozen denies perRealize()call.What this changes
Replaces the open-and-check with
std::filesystem::status()and a permission-bit check for any write bit (owner/group/others).stat()instead ofopen()+close().Compatibility
Semantically equivalent for all current callers.
ScanFiles()only invokesIsFileWriteable()on entries thatrecursive_directory_iteratoralready returned asis_regular_file(), so the non-existent-file edge case doesn't arise in practice. The new code handles it anyway (returnsfalseonstatus()error).No public API change. No header change. Drop-in for all frontends (Apple, Windows, GTK, WASM).
Verification
Built and verified on iOS via the Dasher Apple keyboard extension. Sandbox denies during
Realize()are gone; no regressions in DasherApp, DasherMac, or DasherVision.