fix(openfiles): share descriptors across cloned shell contexts

[reubeno]

Addresses file-descriptor exhaustion in brush by mapping shell "FD" cloning to cloning an Arc-shared OS resource, rather than duplicating the host fd.

[github-actions]

Test Results

    5 files     40 suites   16m 32s ⏱️
2 487 tests 2 487 ✅ 0 💤 0 ❌
7 730 runs  7 730 ✅ 0 💤 0 ❌

Results for commit a4f0e7b.

♻️ This comment has been updated with latest results.

[github-actions]

Public API changes for crate: brush-core

Removed items

-pub fn brush_core::openfiles::OpenFile::try_clone(&self) -> core::result::Result<Self, std::io::error::Error>
-impl core::convert::From<brush_core::openfiles::OpenFile> for std::process::Stdio
-pub fn std::process::Stdio::from(brush_core::openfiles::OpenFile) -> Self

Added items

+impl core::convert::TryFrom<brush_core::openfiles::OpenFile> for std::process::Stdio
+pub type std::process::Stdio::Error = brush_core::error::Error
+pub fn std::process::Stdio::try_from(brush_core::openfiles::OpenFile) -> core::result::Result<Self, Self::Error>

Changed items

-pub brush_core::openfiles::OpenFile::File(std::fs::File)
+pub brush_core::openfiles::OpenFile::File(alloc::sync::Arc<std::fs::File>)
-pub brush_core::openfiles::OpenFile::PipeReader(std::io::pipe::PipeReader)
+pub brush_core::openfiles::OpenFile::PipeReader(alloc::sync::Arc<std::io::pipe::PipeReader>)
-pub brush_core::openfiles::OpenFile::PipeWriter(std::io::pipe::PipeWriter)
+pub brush_core::openfiles::OpenFile::PipeWriter(alloc::sync::Arc<std::io::pipe::PipeWriter>)

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
clone_shell_object	17.79 μs	17.57 μs	-0.21 μs	⚪ Unchanged
eval_arithmetic	0.15 μs	0.15 μs	0.00 μs	⚪ Unchanged
expand_one_string	1.69 μs	1.72 μs	0.03 μs	⚪ Unchanged
for_loop	30.97 μs	31.14 μs	0.17 μs	⚪ Unchanged
full_peg_complex	56.23 μs	56.49 μs	0.26 μs	⚪ Unchanged
full_peg_for_loop	6.22 μs	6.19 μs	-0.03 μs	⚪ Unchanged
full_peg_nested_expansions	16.57 μs	16.54 μs	-0.04 μs	⚪ Unchanged
full_peg_pipeline	4.25 μs	4.18 μs	-0.07 μs	🟢 -1.60%
full_peg_simple	1.76 μs	1.74 μs	-0.02 μs	⚪ Unchanged
function_call	3.58 μs	3.53 μs	-0.05 μs	⚪ Unchanged
instantiate_shell	55.77 μs	55.81 μs	0.04 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	28656.67 μs	28164.84 μs	-491.83 μs	⚪ Unchanged
parse_peg_bash_completion	2104.35 μs	2086.90 μs	-17.45 μs	⚪ Unchanged
parse_peg_complex	18.92 μs	18.96 μs	0.04 μs	⚪ Unchanged
parse_peg_for_loop	1.86 μs	1.85 μs	-0.01 μs	⚪ Unchanged
parse_peg_pipeline	1.99 μs	1.93 μs	-0.06 μs	🟢 -3.21%
parse_peg_simple	1.06 μs	1.03 μs	-0.04 μs	⚪ Unchanged
run_echo_builtin_command	17.37 μs	15.27 μs	-2.10 μs	🟢 -12.11%
tokenize_sample_script	3.56 μs	3.48 μs	-0.09 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-builtins/src/ulimit.rs	🟠 66%	🟠 68.67%	🟢 2.67%
brush-core/src/commands.rs	🟢 91.47%	🟢 91.37%	🔴 -0.1%
brush-core/src/interp.rs	🟢 93%	🟢 92.99%	🔴 -0.01%
brush-core/src/jobs.rs	🟠 50.68%	🟠 51.13%	🟢 0.45%
brush-core/src/openfiles.rs	🟠 63.64%	🟠 64.15%	🟢 0.51%
brush-core/src/shell/io.rs	🟢 83.67%	🟢 82.98%	🔴 -0.69%
brush-parser/src/ast.rs	🔴 46.26%	🔴 48.31%	🟢 2.05%
Overall Coverage	🟢 74.32%	🟢 74.42%	🟢 0.1%

Minimum allowed coverage is 70%, this run produced 74.42%
Maximum allowed coverage difference is -5%, this run produced 0.1%

Test Summary: bash-completion test suite

Outcome	Count	Percentage
✅ Pass	1582	75.01
❗️ Error	18	0.85
❌ Fail	155	7.35
⏩ Skip	339	16.07
❎ Expected Fail	13	0.62
✔️ Unexpected Pass	2	0.09
📊 Total	2109	100.00

[Copilot]

Pull request overview

This PR addresses file-descriptor exhaustion in brush by switching cloned shell contexts to share inherited open file descriptors (instead of duplicating them), which is important because brush runs many “subshell-like” constructs as in-process tasks sharing one process-wide fd table.

Changes:

• Add compatibility regression tests that stress nested/concurrent constructs under a lowered ulimit -n.
• Rework OpenFile cloning semantics to share underlying file/pipe descriptors via Arc, only duplicating when needed for external child processes.
• Adjust redirection and command-spawn plumbing to align with shared-descriptor behavior (including making OpenFile -> Stdio conversion fallible).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
brush-shell/tests/cases/compat/fd_management.yaml	Adds regression cases to catch fd exhaustion under concurrency/nesting.
brush-core/src/shell/io.rs	Avoids cloning trace fd on each write; writes directly to the selected open file.
brush-core/src/shell/fs.rs	Stops duplicating /dev/fd/N opens; reuses the referenced fd’s OpenFile.
brush-core/src/openfiles.rs	Switches file/pipe handles to Arc sharing; updates child-process handoff to duplicate explicitly and makes Stdio conversion fallible.
brush-core/src/interp.rs	Updates redirection setup to share OpenFiles rather than try_clone()-duplicating them.
brush-core/src/commands.rs	Avoids cloning execution parameters for function invocation; executes with shared params reference.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.