devenv: fix execing into a shell with devenv shell

[sandydoo]

The recent async-ification broke interactive shells here: something to do with tokio's Command differences.

Switching to exec here to maximize compatibility with interactive shells.

Fixes #2006.

[claude]

Claude finished @sandydoo's task —— View job

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Code Review for PR #2007: Fix execing into shell with devenv shell

Review Checklist:

• Read repository guidelines and understand codebase structure
• Analyze changes in devenv-run-tests/src/main.rs
• Analyze changes in devenv/src/devenv.rs
• Analyze changes in devenv/src/main.rs
• Assess code quality and adherence to best practices
• Identify potential bugs or issues
• Evaluate performance implications
• Check for security concerns
• Assess test coverage and suggest improvements
• Provide comprehensive review feedback

Review Findings

Code Organization and API Design

The changes introduce a cleaner separation of concerns with two distinct methods:

• exec_in_shell(): Uses exec() to replace the current process (for interactive shells)
• run_in_shell(): Uses spawn() to run commands and return output

This addresses the asyncification issue by properly handling interactive shells through process replacement rather than attempting to capture output.

Issues and Recommendations

1. Inconsistent Error Handling Pattern
devenv/src/main.rs:99 - The simplified error handling may mask exit codes:

Some(cmd) => devenv.exec_in_shell(Some(cmd), args).await,

Issue: When exec_in_shell succeeds, it never returns (process is replaced), but if it fails, the error is propagated without preserving the original command's exit code.

Recommendation: Consider handling the error case more explicitly to preserve exit codes or document that exec failures are treated as devenv errors.

2. Function Signature Inconsistency
devenv/src/devenv.rs:398 - exec_in_shell uses Option<String> while run_in_shell uses String:

pub async fn exec_in_shell(&self, cmd: Option<String>, args: &[String]) -> Result<()>
pub async fn run_in_shell(&self, cmd: String, args: &[String]) -> Result<()>

Issue: This creates cognitive overhead for API users who need to remember which function accepts optional commands.

Recommendation: Consider making both functions consistent, either by:

• Making run_in_shell accept Option<String> and handle the None case appropriately
• Or creating separate functions for interactive shell vs command execution

3. Documentation Clarity
The documentation for exec_in_shell is good but could be improved:
Issue: The return type explanation could confuse users about when to expect Ok(()).

Recommendation: Add a note that callers should not expect Ok(()) in normal operation, only in error cases.

4. Method Naming Inconsistency
devenv-run-tests/src/main.rs:210 - Changed from exec_in_shell to run_in_shell:
Issue: The test runner needs output capture, so run_in_shell is correct here, but the original naming suggests the developer initially intended to use exec.

Recommendation: This change is correct but highlights the need for clearer API naming conventions.

Security Considerations

No major security issues identified. The use of exec() is appropriate for shell operations and doesn't introduce new attack vectors.

Performance Implications

Positive: Using exec() for interactive shells is more efficient than spawn() + wait() as it avoids creating an intermediate process.

Neutral: The changes don't introduce performance regressions.

Test Coverage Gaps

Issue: No tests validate the new exec_in_shell vs run_in_shell distinction.

Recommendations:

1. Add integration tests verifying interactive shell behavior
2. Add tests ensuring run_in_shell properly captures output
3. Add tests for error handling in both methods
4. Consider adding tests for the shell environment setup

Missing Error Context

devenv/src/devenv.rs:407 - Error message construction is good but could be more helpful:

bail!("Failed to exec into shell with {}: {}", cmd_context, err);

Recommendation: Consider adding suggestions for common failures (e.g., "ensure shell is available in PATH").

Code Quality

Positive aspects:

• Good separation of concerns
• Clear documentation
• Follows Rust conventions
• Proper error handling with bail!

Areas for improvement:

• Function signature consistency
• Error message helpfulness
• Test coverage

Overall Assessment

This PR successfully addresses the async-ification issue by providing appropriate abstractions for different shell interaction patterns. The core fix is sound, but the API design could be more consistent and the test coverage should be improved.

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