Windows: don't error if `access_mode` is set on `OpenOptions` by ChrisDenton · Pull Request #162984 · rust-lang/rust

ChrisDenton · 2026-09-18T19:15:43Z

In RFC 1252 it was decided to artificially restrict the combination of File access modes and creation modes for the sake of cross-platform compatibility. This is tested in library/std/src/fs/tests.rs. As the RFC says, using platform specific function should allow overriding this.

On Windows, access_mode does indeed override read, write and append. However currently OpenOptions can still error if you don't use read, write or append. For example:

use std::os::windows::fs::OpenOptionsExt;
File::options()
    .create_new(true)
    .write(true) // useless except it prevents std from erroring
    .access_mode(0)

This PR makes it so you don't need the misleading write(true).

I also cleaned up the error handling for the access mode a bit. It was unnecessarily split between two functions.

rustbot · 2026-09-18T19:15:49Z

r? @clarfonthey

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clarfonthey · 2026-09-20T14:50:23Z

So, just looking at this code, I'm a little confused why the existing code doesn't already work, since the (.., Some(mode)) branch should be equivalent to the if let Some(mode) you changed it to?

Branches are followed in order, and the other branches even explicitly mention that you need None to make them work, so, I don't know why this wouldn't apply.

clarfonthey · 2026-09-20T14:51:29Z

Like, for reviewability purposes, it would be helpful if you left everything in the previous match format at least for one commit so I can more easily tell what the difference is, then you can add a second commit refactoring out the if let if you like.

clarfonthey · 2026-09-20T14:53:05Z

@rustbot author

ChrisDenton · 2026-09-20T15:22:17Z

I've added an intermediate commit so that the diff is more readable.

Moving the access_mode case out of the match does seem more reasonable to me because it's logically a different thing. It's either use the given access mode or else infer the access mode from read, write and append. The first and second things should not interact at all.

ChrisDenton · 2026-09-20T15:22:54Z

@rustbot ready

clarfonthey · 2026-09-20T16:44:05Z

Okay, yes, this is much easier to understand now. This looks good to me, especially with the motivation provided.

@bors try jobs=x86_64-msvc-*

(just because I keep getting burned by this…)

Windows: don't error if `access_mode` is set on `OpenOptions` try-job: x86_64-msvc-*

rust-bors · 2026-09-20T16:45:12Z

💔 Test for 3f2aae8 failed: CI. Failed job:

Calculate job matrix (web logs, enhanced plaintext logs)

rust-log-analyzer · 2026-09-20T16:45:15Z

A job failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

   Compiling glob-match v0.2.1
   Compiling citool v0.1.0 (/home/runner/work/rust/rust/src/ci/citool)
    Finished `dev` profile [unoptimized] target(s) in 33.48s
     Running `target/debug/citool calculate-job-matrix`
Run type: TryJob { job_patterns: Some(["x86_64-msvc-*"]), nolimit: false }
Error: Failed to calculate job matrix

Caused by:
    Patterns `x86_64-msvc-*` did not match any auto jobs
##[error]Process completed with exit code 1.
Post job cleanup.

ChrisDenton · 2026-09-20T16:51:22Z

I do test locally but fair enough. Btw, job names have changed

@bors try jobs=test-x86_64-msvc-*

Windows: don't error if `access_mode` is set on `OpenOptions` try-job: test-x86_64-msvc-*

clarfonthey · 2026-09-20T16:51:52Z

@bors try jobs=test-x86_64-msvc-*

🙃

Windows: don't error if `access_mode` is set on `OpenOptions` try-job: test-x86_64-msvc-*

rust-bors · 2026-09-20T19:49:45Z

☀️ Try build successful (CI)
Build commit: 80f06fa (80f06fac542312ae886904376699bc6ce55753c5)
Base parent: 12c4d3f (12c4d3f34dcb4715784d2fa0e8443853e0592194)

clarfonthey · 2026-09-21T02:12:42Z

@bors r+ rollup

Thanks as always, just superstitious about Windows PRs randomly failing at this point :p

rust-bors · 2026-09-21T02:12:44Z

📌 Commit 39f76c9 has been approved by clarfonthey

It is now in the queue for this repository.

…fonthey Windows: don't error if `access_mode` is set on `OpenOptions` In [RFC 1252] it was decided to artificially restrict the combination of `File` access modes and creation modes for the sake of cross-platform compatibility. This is tested in [`library/std/src/fs/tests.rs`]. As the RFC says, using platform specific function should allow overriding this. On Windows, [`access_mode`] does indeed override `read`, `write` and `append`. However currently `OpenOptions` can still error if you don't use `read`, `write` or `append`. For example: ```rust use std::os::windows::fs::OpenOptionsExt; File::options() .create_new(true) .write(true) // useless except it prevents std from erroring .access_mode(0) ``` This PR makes it so you don't need the misleading `write(true)`. I also cleaned up the error handling for the access mode a bit. It was unnecessarily split between two functions. [RFC 1252]: https://rust-lang.github.io/rfcs/1252-open-options.html#combination-of-access-modes-and-creation-modes [`library/std/src/fs/tests.rs`]: https://github.com/rust-lang/rust/blob/420ed2a0c3d7225b1744266fd884d431b4d8cfe0/library/std/src/fs/tests.rs#L1517 [`access_mode`]: https://doc.rust-lang.org/stable/std/os/windows/fs/trait.OpenOptionsExt.html#tymethod.access_mode

Rollup of 15 pull requests Successful merges: - #161051 (When error from local macro, include macro def span) - #162750 (add case mapping fast paths for Latin-1) - #162831 (Do not continue past `rustc_resolve` when encountering duplicated items) - #162835 (rustdoc: account for nested parens and split text events in bare urls lint) - #163044 (Report runtime range endpoints for runtime values) - #163062 (Use x30 register name with LLVM 23+) - #158102 (When compiling without a specified `--edition`, emit a note) - #162984 (Windows: don't error if `access_mode` is set on `OpenOptions`) - #163005 (Avoid unreachable integer underflow check in `CStr::count_bytes()`) - #163019 (Prepare for the introduction of forced keywords (`k#`)) - #163020 (Dir: fix fallback impl for remove_dir) - #163047 (Use verbose suggestion for `mut binding` instead of `&mut binding`) - #163075 (Fix ArgAttributes mismatches in ABI UI tests for LoongArch64 and RiscV64) - #163079 (enable `f128` from `u64`/`i64` test) - #163082 (Remove `TypeChecker::root_cx`)

…fonthey Windows: don't error if `access_mode` is set on `OpenOptions` In [RFC 1252] it was decided to artificially restrict the combination of `File` access modes and creation modes for the sake of cross-platform compatibility. This is tested in [`library/std/src/fs/tests.rs`]. As the RFC says, using platform specific function should allow overriding this. On Windows, [`access_mode`] does indeed override `read`, `write` and `append`. However currently `OpenOptions` can still error if you don't use `read`, `write` or `append`. For example: ```rust use std::os::windows::fs::OpenOptionsExt; File::options() .create_new(true) .write(true) // useless except it prevents std from erroring .access_mode(0) ``` This PR makes it so you don't need the misleading `write(true)`. I also cleaned up the error handling for the access mode a bit. It was unnecessarily split between two functions. [RFC 1252]: https://rust-lang.github.io/rfcs/1252-open-options.html#combination-of-access-modes-and-creation-modes [`library/std/src/fs/tests.rs`]: https://github.com/rust-lang/rust/blob/420ed2a0c3d7225b1744266fd884d431b4d8cfe0/library/std/src/fs/tests.rs#L1517 [`access_mode`]: https://doc.rust-lang.org/stable/std/os/windows/fs/trait.OpenOptionsExt.html#tymethod.access_mode

…uwer Rollup of 18 pull requests Successful merges: - #161051 (When error from local macro, include macro def span) - #161629 (Streamline `StateDiffCollector`) - #162750 (add case mapping fast paths for Latin-1) - #162831 (Do not continue past `rustc_resolve` when encountering duplicated items) - #162835 (rustdoc: account for nested parens and split text events in bare urls lint) - #162952 (Depend on lockfiles to prevent GC of the current session) - #163044 (Report runtime range endpoints for runtime values) - #163062 (Use x30 register name with LLVM 23+) - #158102 (When compiling without a specified `--edition`, emit a note) - #162939 (Declare multi-kind constants for MacroKinds) - #162984 (Windows: don't error if `access_mode` is set on `OpenOptions`) - #163005 (Avoid unreachable integer underflow check in `CStr::count_bytes()`) - #163019 (Prepare for the introduction of forced keywords (`k#`)) - #163020 (Dir: fix fallback impl for remove_dir) - #163047 (Use verbose suggestion for `mut binding` instead of `&mut binding`) - #163075 (Fix ArgAttributes mismatches in ABI UI tests for LoongArch64 and RiscV64) - #163079 (enable `f128` from `u64`/`i64` test) - #163082 (Remove `TypeChecker::root_cx`)

…uwer Rollup of 19 pull requests Successful merges: - #161051 (When error from local macro, include macro def span) - #161629 (Streamline `StateDiffCollector`) - #162750 (add case mapping fast paths for Latin-1) - #162831 (Do not continue past `rustc_resolve` when encountering duplicated items) - #162835 (rustdoc: account for nested parens and split text events in bare urls lint) - #162952 (Depend on lockfiles to prevent GC of the current session) - #163044 (Report runtime range endpoints for runtime values) - #163062 (Use x30 register name with LLVM 23+) - #163091 (miri subtree update) - #162939 (Declare multi-kind constants for MacroKinds) - #162984 (Windows: don't error if `access_mode` is set on `OpenOptions`) - #163005 (Avoid unreachable integer underflow check in `CStr::count_bytes()`) - #163019 (Prepare for the introduction of forced keywords (`k#`)) - #163020 (Dir: fix fallback impl for remove_dir) - #163041 (Be more explicit on suggestion type without changing how they are rendered) - #163047 (Use verbose suggestion for `mut binding` instead of `&mut binding`) - #163075 (Fix ArgAttributes mismatches in ABI UI tests for LoongArch64 and RiscV64) - #163079 (enable `f128` from `u64`/`i64` test) - #163082 (Remove `TypeChecker::root_cx`)

Rollup merge of #162984 - ChrisDenton:access-allowed, r=clarfonthey Windows: don't error if `access_mode` is set on `OpenOptions` In [RFC 1252] it was decided to artificially restrict the combination of `File` access modes and creation modes for the sake of cross-platform compatibility. This is tested in [`library/std/src/fs/tests.rs`]. As the RFC says, using platform specific function should allow overriding this. On Windows, [`access_mode`] does indeed override `read`, `write` and `append`. However currently `OpenOptions` can still error if you don't use `read`, `write` or `append`. For example: ```rust use std::os::windows::fs::OpenOptionsExt; File::options() .create_new(true) .write(true) // useless except it prevents std from erroring .access_mode(0) ``` This PR makes it so you don't need the misleading `write(true)`. I also cleaned up the error handling for the access mode a bit. It was unnecessarily split between two functions. [RFC 1252]: https://rust-lang.github.io/rfcs/1252-open-options.html#combination-of-access-modes-and-creation-modes [`library/std/src/fs/tests.rs`]: https://github.com/rust-lang/rust/blob/420ed2a0c3d7225b1744266fd884d431b4d8cfe0/library/std/src/fs/tests.rs#L1517 [`access_mode`]: https://doc.rust-lang.org/stable/std/os/windows/fs/trait.OpenOptionsExt.html#tymethod.access_mode

…uwer Rollup of 19 pull requests Successful merges: - rust-lang/rust#161051 (When error from local macro, include macro def span) - rust-lang/rust#161629 (Streamline `StateDiffCollector`) - rust-lang/rust#162750 (add case mapping fast paths for Latin-1) - rust-lang/rust#162831 (Do not continue past `rustc_resolve` when encountering duplicated items) - rust-lang/rust#162835 (rustdoc: account for nested parens and split text events in bare urls lint) - rust-lang/rust#162952 (Depend on lockfiles to prevent GC of the current session) - rust-lang/rust#163044 (Report runtime range endpoints for runtime values) - rust-lang/rust#163062 (Use x30 register name with LLVM 23+) - rust-lang/rust#163091 (miri subtree update) - rust-lang/rust#162939 (Declare multi-kind constants for MacroKinds) - rust-lang/rust#162984 (Windows: don't error if `access_mode` is set on `OpenOptions`) - rust-lang/rust#163005 (Avoid unreachable integer underflow check in `CStr::count_bytes()`) - rust-lang/rust#163019 (Prepare for the introduction of forced keywords (`k#`)) - rust-lang/rust#163020 (Dir: fix fallback impl for remove_dir) - rust-lang/rust#163041 (Be more explicit on suggestion type without changing how they are rendered) - rust-lang/rust#163047 (Use verbose suggestion for `mut binding` instead of `&mut binding`) - rust-lang/rust#163075 (Fix ArgAttributes mismatches in ABI UI tests for LoongArch64 and RiscV64) - rust-lang/rust#163079 (enable `f128` from `u64`/`i64` test) - rust-lang/rust#163082 (Remove `TypeChecker::root_cx`)

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 18, 2026

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ChrisDenton force-pushed the access-allowed branch from 0da2a41 to ed4fe76 Compare September 18, 2026 19:43

ChrisDenton added O-windows Operating system: Windows A-io Area: `std::io`, `std::fs`, `std::net` and `std::path` labels Sep 18, 2026

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 20, 2026

ChrisDenton added 3 commits September 20, 2026 15:06

Test windows access_mode override

21d6920

Windows: don't error if access_mode is set

ac5ff45

Refactor access_mode case out of match

39f76c9

ChrisDenton force-pushed the access-allowed branch from ed4fe76 to 39f76c9 Compare September 20, 2026 15:22

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Auto merge of #162984 - ChrisDenton:access-allowed, r=<try>

3f2aae8

Windows: don't error if `access_mode` is set on `OpenOptions` try-job: x86_64-msvc-*

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Auto merge of #162984 - ChrisDenton:access-allowed, r=<try>

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Windows: don't error if `access_mode` is set on `OpenOptions` try-job: test-x86_64-msvc-*

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Auto merge of #162984 - ChrisDenton:access-allowed, r=<try>

80f06fa

Windows: don't error if `access_mode` is set on `OpenOptions` try-job: test-x86_64-msvc-*

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Zalathar mentioned this pull request Sep 21, 2026

Rollup of 15 pull requests #163086

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JonathanBrouwer mentioned this pull request Sep 21, 2026

Rollup of 18 pull requests #163089

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JonathanBrouwer mentioned this pull request Sep 21, 2026

Rollup of 19 pull requests #163095

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rust-bors Bot merged commit 042e9bc into rust-lang:main Sep 21, 2026
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rustbot added this to the 1.100.0 milestone Sep 21, 2026

ChrisDenton deleted the access-allowed branch September 21, 2026 13:33

github-actions Bot mentioned this pull request Oct 2, 2026

Toolchain upgrade to nightly-2026-09-25 flux-rs/flux#1803

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