fix: handle nil Process when exec command doesn't exist

[tobert]

Summary

Fixes crash when running otel-cli exec with a non-existent command by properly handling nil Process and ProcessState.

Problem

Running otel-cli exec command-that-does-not-exist resulted in a panic:

panic: runtime error: invalid memory address or nil pointer dereference

The crash occurred because when a command fails to start (e.g., command not found), child.Process and child.ProcessState are nil, but the code attempted to dereference them without checking.

Solution

Added nil checks before dereferencing:

• Check child.Process != nil before accessing Pid
• Check child.ProcessState != nil before getting ExitCode
• Return exit code 127 when command fails to start (matches shell behavior for "command not found")
• Still sends span with error status

Behavior

Principle of least surprise: otel-cli exec now behaves like running the command directly:

$ command-that-does-not-exist
bash: command-that-does-not-exist: command not found
$ echo $?
127

$ otel-cli exec command-that-does-not-exist
$ echo $?
127  # ✅ matches shell behavior

Testing

Added integration test that verifies:

• ✅ No panic/crash
• ✅ Exit code 127 (matches shell)
• ✅ Span is sent with error status
• ✅ Error message contains "exec command failed"

Related

Fixes #8

🤖 Generated with Claude Code

Co-Authored-By: Claude claude@anthropic.com

[Copilot]

Pull Request Overview

This PR fixes a nil pointer dereference panic that occurred when otel-cli exec is invoked with a non-existent command. The fix adds proper nil checks for Process and ProcessState before dereferencing them, and returns exit code 127 (matching standard shell behavior for "command not found") when a command fails to start.

Key changes:

• Added nil check for child.Process before accessing Pid
• Added nil check for child.ProcessState before calling ExitCode(), with fallback to exit code 127
• Added integration test to verify the fix prevents panic and returns correct exit code

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
otelcli/exec.go	Added nil checks for Process and ProcessState to prevent panic, with exit code 127 fallback
data_for_test.go	Added integration test verifying non-existent command handling

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