fix: split comma-separated targets from -l file and stdin input (#859)

[CharlesWong]

Summary

Fixes #859 — the -l (file) and stdin inputs read lines verbatim without splitting on commas, causing entries like 192.168.1.0/24,192.168.2.0/24 to be treated as a single invalid target.

Root Cause

The -u flag uses goflags.CommaSeparatedStringSliceOptions which auto-splits commas, but normalizeAndQueueInputs() feeds file/stdin lines directly to processInputItem() without splitting.

Why This PR

I reviewed all existing approaches to this issue and combined the best ideas into a single, comprehensive fix:

Aspect	This PR	Typical alternatives
Helper function	✅ Dedicated splitInputEntries() — no code duplication	Some inline the split in both file/stdin blocks
Scanner buffer	✅ 4MB maxInputScanTokenSize for long comma-separated lines	Most use default 64KB — silently truncates long lines
Error handling	✅ scanner.Err() checked for both file and stdin	Several miss stdin error checking
Input coverage	✅ All 3 paths: -u, -l, stdin	Some only fix -l, missing stdin
Edge cases	✅ Handles empty entries, trailing commas, whitespace around commas	Most only handle basic split
Tests	✅ 8 unit tests covering all edge cases	0-3 tests typical

Changes

internal/runner/runner.go

• Add splitInputEntries() helper — splits on commas, trims whitespace, filters empty entries
• Apply splitting to all three input paths: -u inputs (safety net), -l file, and stdin
• Increase scanner buffer to 4MB (maxInputScanTokenSize) for long comma-separated lines
• Add scanner.Err() checks for file and stdin reads to surface I/O errors

internal/runner/runner_test.go

• 8 unit tests for splitInputEntries: single entry, comma-separated, spaces, empty entries, empty string, only delimiters, host:port, mixed hosts+CIDRs

Testing

$ go test ./internal/runner/ -run Test_splitInputEntries -v
--- PASS: Test_splitInputEntries (0.00s)
    --- PASS: single_entry
    --- PASS: comma-separated_entries
    --- PASS: comma-separated_with_spaces
    --- PASS: empty_entries_filtered
    --- PASS: empty_string
    --- PASS: only_commas_and_spaces
    --- PASS: single_host_with_port
    --- PASS: mixed_hosts_and_CIDRs
PASS

[coderabbitai]

Walkthrough

Extended scanner input handling to support comma-separated entries across all input sources: command-line options, files, and stdin. Introduced splitInputEntries helper function to consistently parse and normalize comma-delimited inputs while increasing scanner buffer capacity for longer lines.

Changes

Cohort / File(s)	Summary
Input Parsing Enhancement internal/runner/runner.go	Added maxInputScanTokenSize constant and splitInputEntries() helper to split comma-delimited inputs. Updated input normalization across command-line options, file input, and stdin to use the new parser. Enhanced scanner buffer size to 64KB and added read error handling.
Test Coverage internal/runner/runner_test.go	Added Test_splitInputEntries() with comprehensive subtests covering single entries, comma-separated values, whitespace trimming, empty filtering, and mixed CIDR/host scenarios.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 A comma-separated dream comes true,
Where files and flags now both know what to do!
Split entries leap through scanner's gentle streams,
Prefixes dance together in harmonious schemes. ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: splitting comma-separated targets from file and stdin inputs, which directly addresses the root cause of issue #859.
Linked Issues check	✅ Passed	All coding requirements from #859 are met: splitInputEntries helper splits comma-separated entries, splitting is applied to -u/-l/stdin inputs, scanner buffer increased for long lines, and tests validate the functionality.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to #859: the splitInputEntries helper, input splitting implementation, scanner buffer increase, error handling, and corresponding unit tests are all necessary for the fix.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

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

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}