host_env: os.mkdir for Windows, Redox#8128

joshuamegnauth54

Python supports mkdir on Windows. I deferred to calling Rust's implementation for now. However, like rename, Python's implementation supports additional features that are currently unsupported on RustPython. I added a note for future reference.

Redox supports mkdirat which significantly cleans up the implementation.

Closes #xxxx
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Summary

Windows support for os.mkdir
Deduplicate Unix implementation

On a related note, I think the WASI Posix and Unix implementations can be combined eventually. 🤔

Summary by CodeRabbit

Refactor
- Unified directory creation interface across platforms for improved consistency and maintainability.

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📝 Walkthrough

Walkthrough

The PR unifies the directory-creation API in host_env: the separate make_dir(&CStr, mode) and make_dir_at(i32, &CStr, mode) functions are replaced by a single make_dir(Option<crt_fd::Borrowed<'_>>, &Path, mode) in both posix.rs and posix_wasi.rs, with rustix::fs::mkdirat as the backend. The os stdlib mkdir implementation and platform capability flags are updated to use the new signature.

Changes

Unified make_dir API refactor

Layer / File(s)	Summary
New `make_dir` signature in `posix.rs` and `posix_wasi.rs` `crates/host_env/src/posix.rs`, `crates/host_env/src/posix_wasi.rs`	Adds `use crate::crt_fd` import; replaces old `make_dir(&CStr)`/`make_dir_at(i32, &CStr)` pair with a single `make_dir(Option<crt_fd::Borrowed<'_>>, &Path, mode)`. Non-Unix falls back to `std::fs::create_dir` or returns `Unsupported`; Unix and WASI delegate to `rustix::fs::mkdirat` with `CWD` when no fd is given.
`os` stdlib `mkdir` caller and platform flags `crates/vm/src/stdlib/os.rs`	Simplifies `cfg_select!` `AT_FDCWD` condition to `any(unix, target_os = "wasi")`, changes `MKDIR_DIR_FD` from non-windows/non-redox to `cfg!(unix)`, adds `Path` to `std` imports, and rewrites `mkdir` to call `host_env::posix::make_dir` with `dir_fd.get_opt()` and `Path::new`.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

RustPython/RustPython#7604: Introduced the crt_fd::Borrowed abstraction and the original make_dir/make_dir_at implementations that this PR directly replaces.
RustPython/RustPython#7636: Also modifies the cfg_select! AT_FDCWD/directory-fd fallback condition in crates/vm/src/stdlib/os.rs.

Suggested reviewers

youknowone

🐇 Hop, hop, hooray for paths so clean,
No more raw i32 hiding between!
Option<Borrowed> and &Path now unite,
mkdirat hums with rustix delight.
One make_dir to rule them all tonight! 🌿

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Title check	⚠️ Warning	The title references Windows and Redox support, but the actual changes focus on refactoring the `make_dir` API to accept optional directory file descriptors and changing platform conditionals for Unix/non-Unix, not primarily adding Windows/Redox support.	Consider retitling to reflect the core changes, e.g., 'Refactor make_dir API to support optional directory file descriptors' or 'Simplify make_dir with unified API for directory operations'.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@crates/host_env/src/posix_wasi.rs`:
- Around line 4-10: The make_dir function uses &Path as a parameter type, but
Path is not imported from the standard library, causing a compilation error. Add
path::Path to the existing std imports at the top of the file where ffi::OsStr
and io are already imported to bring Path into scope.

In `@crates/vm/src/stdlib/os.rs`:
- Line 191: The MKDIR_DIR_FD constant in the os.rs file is currently configured
only for unix systems using cfg!(unix), but since WASI now supports the optional
dir_fd parameter in make_dir function as implemented in posix_wasi.rs, the cfg
condition needs to be updated. Modify the MKDIR_DIR_FD constant definition to
also include WASI targets in the condition so that dir_fd functionality is
enabled on WASI systems where it is now supported.

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📥 Commits

Reviewing files that changed from the base of the PR and between fe2a7db and 9e4a98a.

📒 Files selected for processing (3)

crates/host_env/src/posix.rs
crates/host_env/src/posix_wasi.rs
crates/vm/src/stdlib/os.rs

Python supports `mkdir` on Windows. I deferred to calling Rust's implementation for now. However, like `rename`, Python's implementation supports additional features that are currently unsupported on RustPython. I added a note for future reference. Redox supports `mkdirat` which significantly cleans up the implementation.

coderabbitai Bot reviewed Jun 18, 2026

View reviewed changes

joshuamegnauth54 marked this pull request as draft June 18, 2026 01:27

joshuamegnauth54 force-pushed the host_env-mkdir branch 3 times, most recently from d408aea to be40b57 Compare June 19, 2026 00:49

joshuamegnauth54 force-pushed the host_env-mkdir branch from be40b57 to af2dbfb Compare June 19, 2026 00:50

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host_env: os.mkdir for Windows, Redox#8128