Handle OsError in REPL #6187

doojonio · 2025-10-11T12:54:23Z

Summary by CodeRabbit

Bug Fixes
- Improved handling of OS-level read errors on Unix when reading input, providing clearer error messages and exiting the prompt loop safely.
- The built-in input function now surfaces OS errors as proper exceptions on Unix instead of ambiguous failures.
- Enhances stability and diagnostics during terminal I/O failures on Unix systems; existing behavior on other platforms remains unchanged.

coderabbitai · 2025-10-11T12:54:57Z

Walkthrough

Introduces a Unix-specific ReadlineResult::OsError variant and integrates handling across readline, the REPL loop, and the builtin input function. On Unix, OS-level readline errors are propagated as OS error exceptions; the REPL prints the error and exits the loop. Existing branches remain unchanged.

Changes

Cohort / File(s)	Summary
Readline result extension (Unix) `vm/src/readline.rs`	Adds `#[cfg(unix)]` variant `OsError(nix::Error)` to `ReadlineResult`. Maps `ReadlineError::Errno(num)` to `OsError(num)` in Unix code paths, updating match branches accordingly.
REPL loop error handling (Unix) `src/shell.rs`	Adds a Unix-only match arm for `ReadlineResult::OsError(num)` in `run_shell`: constructs an OS error exception with the numeric code, prints it, and breaks the loop.
Builtin input error mapping (Unix) `vm/src/stdlib/builtins.rs`	Adds a Unix-only match arm in builtin `input` to convert `ReadlineResult::OsError(num)` into `vm.new_os_error(num.to_string())`.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant U as User
  participant RL as Readline (Unix)
  participant VM as VM
  participant SH as REPL Shell

  rect rgba(230,240,255,0.6)
    U->>SH: Enter input
    SH->>RL: read_line()
    RL-->>SH: OsError(errno)
    note over SH: New Unix-specific branch
    SH->>VM: new_os_error(errno)
    VM-->>SH: OSError instance
    SH-->>U: Print error
    SH-->>U: Exit REPL loop
  end

sequenceDiagram
  autonumber
  participant U as User code
  participant RL as Readline (Unix)
  participant VM as VM
  participant BI as builtin input()

  rect rgba(230,255,230,0.6)
    U->>BI: input()
    BI->>RL: read_line()
    RL-->>BI: OsError(errno)
    note over BI: New Unix-specific arm
    BI->>VM: new_os_error(errno.to_string())
    VM-->>BI: OSError
    BI-->>U: Raise OSError
  end

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

I nudge the keys with velvet paws,
Catch OS winds and Unix laws;
When FDs fall and lines demur,
I whisk an OSError to confer.
No crash tonight—just gentle hop,
A tidy loop, a graceful stop.
🐇✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	You can run `@coderabbitai generate docstrings` to improve docstring coverage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The title “Handle OsError in REPL” succinctly and accurately describes the primary change of adding explicit OS error handling in the REPL without extraneous details or ambiguity.
Linked Issues Check	✅ Passed	The changes introduce a new OsError variant and integrate it into the readline loop and builtin input function so that Errno(EBADF) is caught and raised as an OSError rather than crashing, directly satisfying the objective of issue #6146.
Out of Scope Changes Check	✅ Passed	All modifications are focused solely on introducing and handling the OsError variant under the Unix configuration, with no unrelated code changes detected outside the scope of preventing the REPL crash.

✨ Finishing touches

📝 Generate docstrings

🧪 Generate unit tests (beta)

Create PR with unit tests
Post copyable unit tests in a comment

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coderabbitai

Actionable comments posted: 0

🧹 Nitpick comments (1)

src/shell.rs (1)

212-218: Use vm.new_os_error() for consistency.

For consistency with the handling in builtins.rs (line 493) and cleaner error messages, consider using vm.new_os_error(num.to_string()) instead of manually constructing the exception.

Apply this diff:

-            #[cfg(unix)]
-            ReadlineResult::OsError(num) => {
-                let os_error =
-                    vm.new_exception_msg(vm.ctx.exceptions.os_error.to_owned(), format!("{num:?}"));
-                vm.print_exception(os_error);
-                break;
-            }
+            #[cfg(unix)]
+            ReadlineResult::OsError(num) => {
+                let os_error = vm.new_os_error(num.to_string());
+                vm.print_exception(os_error);
+                break;
+            }

📜 Review details

Configuration used: Path: .coderabbit.yml

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3a6fda4 and 25e0a28.

📒 Files selected for processing (3)

src/shell.rs (1 hunks)
vm/src/readline.rs (2 hunks)
vm/src/stdlib/builtins.rs (1 hunks)

🧰 Additional context used

📓 Path-based instructions (2)

**/*.rs

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

**/*.rs: Format Rust code with the default rustfmt style (run cargo fmt)
Run clippy and fix any warnings or lints introduced by your changes
Follow Rust best practices for error handling and memory management

Files:

vm/src/readline.rs
src/shell.rs
vm/src/stdlib/builtins.rs

{vm,stdlib}/**/*.rs

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

Use RustPython macros (pyclass, pymodule, pyfunction, etc.) when implementing Python functionality in Rust

Files:

vm/src/readline.rs
vm/src/stdlib/builtins.rs

🔇 Additional comments (3)

vm/src/readline.rs (2)

16-17: LGTM!

The Unix-specific OsError variant is properly gated and provides a clean way to propagate OS-level readline errors (such as EBADF when stdout is closed).

123-124: LGTM!

The mapping from ReadlineError::Errno to ReadlineResult::OsError correctly propagates Unix-specific errno errors through the readline interface.

vm/src/stdlib/builtins.rs (1)

492-493: LGTM!

The Unix-specific error handling correctly converts readline OS errors into Python OSError exceptions using the idiomatic vm.new_os_error() method.

youknowone

Thank you for contributing!

Handle OsError in REPL

25e0a28

coderabbitai bot reviewed Oct 11, 2025

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youknowone approved these changes Oct 12, 2025

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youknowone merged commit b56e469 into RustPython:main Oct 13, 2025
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Handle OsError in REPL #6187

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Walkthrough

Changes

Sequence Diagram(s)

Estimated code review effort

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doojonio commented Oct 11, 2025 •

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