mkdir doesn't error on already-existing directory #19003

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1. pickx

   added

   status:needs-triageAn issue that hasn't had any proper lookAn issue that hasn't had any proper look

   on Sep 10, 2026
2. fdncred

   added

   good first issueGood for newcomersGood for newcomers

   on Sep 10, 2026
3. fdncred

   closed this as completedin #19006on Sep 10, 2026
4. github-actions

   added this to the v0.116.0 milestone on Sep 10, 2026
5. pull

   added a commit that references this issue on Sep 10, 2026

   mkdir errors on already-created dir (nushell#19006)

   ...

   This issue will close once commit 954e34d is merged into the 'main' branch.

   954e34d
6. fdncred

   reopened this on Sep 10, 2026
7. Developer1010x commented on Sep 13, 2026

   

   Developer1010x

   on Sep 13, 2026

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   I had a look at this. The cause is one line, but the fix is a design decision rather than a bug fix, so flagging it before writing code.

   crates/nu-command/src/filesystem/umkdir.rs hard-codes

   const IS_RECURSIVE: bool = true;

   and passes it as Config { recursive: IS_RECURSIVE, .. }. In uu_mkdir the "File exists" error is raised only when recursion is off:

   // uu_mkdir 0.11.0, src/mkdir.rs:213
   if path_exists && !config.recursive {
       return Err(USimpleError::new(1, translate!("mkdir-error-file-exists", ...)));
   }

   With recursive: true the existing-directory case instead falls through to an Ok(()) branch, which is where the silent success comes from.

   So mkdir in nushell is always mkdir -p, which is what the description ("with intermediary directories if required") and the creates_intermediary_directories test both say. The comparison in the report is against non--p mkdir — uutils mkdir -p foo on an existing foo also exits 0 and prints nothing, as POSIX requires -p to suppress that error. So "match uutils" points in two different directions depending on which mkdir we mean.

   That leaves roughly three options:

   1. Add --parents/-p and make the default non-recursive. Exactly matches coreutils. Also breaks every mkdir a/b/c in every existing script and config, and creates_intermediary_directories with it. A large breaking change for a command people use constantly.
   2. Keep creating intermediates, but error if the final target already exists. Gives the behavior asked for here. It is not coreutils semantics under any flag combination, and it needs an explicit existence check on the nushell side, since uu_mkdir will not report it in recursive mode.
   3. Leave the behavior and document that nushell's mkdir is mkdir -p.

   One part is a plain bug under all three, though: mkdir --verbose reports created: true for a directory that already existed. Whatever is decided about the exit code, that field is simply wrong — nothing was created. It can be fixed on its own by checking existence before the call and reporting created: false.

   Happy to implement whichever direction you prefer. If it helps to make progress in the meantime, I can put up a small PR for the --verbose created field alone, since that one does not depend on the decision above.
8. Developer1010x commented on Sep 13, 2026

   

   Developer1010x

   on Sep 13, 2026

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   Put up #19017 for the --verbose created field on its own, since that part does not depend on the decision above. The exit-code question is still open — happy to follow up with whichever of the three options you land on.
9. fdncred

   added 2 commits that reference this issue on Sep 13, 2026

   fix(mkdir): don't report an existing directory as created in --verbose (

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   b6e6562

   feat(mkdir): add --fail-if-exists flag to error on existing directory (…

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   f2fdb76
10. sharmis-tp commented on Nov 12, 2026

    

    sharmis-tp

    on Nov 12, 2026

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    I'd like to take this. Will add an existence check in mkdir before the call.
11. fdncred

    closed this as completedon Nov 12, 2026