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Title: vfs: align virtual file handles with open(2) by pipobscure · Pull Request #65854 · nodejs/node · GitHub

Open Graph Title: vfs: align virtual file handles with open(2) by pipobscure · Pull Request #65854 · nodejs/node

X Title: vfs: align virtual file handles with open(2) by pipobscure · Pull Request #65854 · nodejs/node

Description: vfs: align virtual file handles with open(2) A file descriptor obtained on a mounted path answers several node:fs calls differently from one on a real file, in both providers: writeFileSync(path, data, { flag: 'r+' }) replaces the whole file instead of overwriting bytes from offset 0 and keeping the tail. Numeric open flags are mapped by treating any write-ish bit as "w": O_WRONLY alone truncates, and O_RDONLY | O_CREAT opens the file write-only and truncates it. A handle opened with "a+" starts its read offset at the end of the file, so the first read returns nothing; O_APPEND only affects writes. The ZipProvider handle additionally: throws EISDIR instead of EBADF when reading a write-only handle or writing a read-only one; leaves stale bytes in place when ftruncate grows a file that was previously shrunk, where real files read back as zeros; rejects a BigInt position with a TypeError from mixing number and BigInt arithmetic. This adds a test that runs the same sequence of calls against a memory mount and a ZIP mount and expects the real-fs result, so every divergence shows up as its own failing case. Proposed solution: decode numeric flags bit by bit (O_TRUNC decides truncation, O_CREAT decides creation, O_WRONLY/O_RDWR decide access) instead of collapsing them to a flag string; keep the read offset at 0 for append handles and only force writes to the end; make the handle writeFile for non-truncating flags write at offset 0 without shrinking; in the ZIP handle use EBADF for access-mode violations, zero-fill on growth in #doTruncate, and coerce position with Number() as the memory handle does. Note: Since these are gaps/defects in existing functionality, I decided to create the failing tests first (first commit) and then add the fix/solution as a second commit. That way whoever wants to review this can first prove out the issue, before applying the solution. This goes with the VFS work by @mcollina and the bug-fix PRs by @trivikr.

Open Graph Description: vfs: align virtual file handles with open(2) A file descriptor obtained on a mounted path answers several node:fs calls differently from one on a real file, in both providers: writeFileSync(path, ...

X Description: vfs: align virtual file handles with open(2) A file descriptor obtained on a mounted path answers several node:fs calls differently from one on a real file, in both providers: writeFileSync(path, ...

Opengraph URL: https://github.com/nodejs/node/pull/65854

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