fix: JSON/CSV output empty for host discovery scans (#1611)

[sheikhshaheerimran]

Summary

• Fixes JSON output being empty when running host discovery scans
• Fixes CSV output being empty when running host discovery scans
• Applies to both console and file output

Closes #1611

Test plan

• sudo ./naabu -host hackerone.com -json -sn shows JSON output
• sudo ./naabu -host hackerone.com -csv -sn shows CSV output
• sudo ./naabu -host hackerone.com -json -sn -o out.json writes to file
• sudo ./naabu -host hackerone.com -csv -sn -o out.csv writes to file
• Regular port scanning still works: ./naabu -host hackerone.com -p 80,443 -json
• All existing tests pass

Summary by CodeRabbit

• Bug Fixes
  • JSON and CSV outputs now reliably produce a result even when no ports are detected — JSON emits a single object with a trailing newline, and CSV emits at least one row.
  • CSV headers are initialized once per output sequence and rows are consistently written and flushed, improving formatting and consistency across result sets.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

Output logic in pkg/runner/output.go and pkg/runner/runner.go was changed so zero-port results now emit a single JSON object or CSV row instead of producing no output; JSON and CSV streaming paths were adjusted to batch-format output into a buffer before printing.

Changes

Cohort / File(s)	Summary
Zero-port output handling pkg/runner/output.go	When ports list is empty, WriteJSONOutputWithMac writes one JSON object plus newline; CSV functions emit one pre-initialized CSV row instead of skipping emission.
Streaming & buffering pkg/runner/runner.go	handleOutput now marshals per-item JSON bytes into a buffer and prints them; CSV path initializes headers once and writes rows via writeCSVRow with buffered flush instead of per-port direct emission.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

I’m a rabbit in the code-lined glen,
Hop-scanning hosts again and then.
Where silence lived with ports of none,
A JSON line now greets the sun. 🐇
Hooray—each host’s small song is done.

Pre-merge checks and finishing touches

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title clearly and specifically describes the main change: fixing empty JSON/CSV output for host discovery scans, matching the core issue being addressed.
Linked Issues check	✅ Passed	The code changes ensure host-discovery results are now serialized in JSON/CSV formats by modifying output handling to emit data even when ports list is empty, directly addressing issue #1611's requirement.
Out of Scope Changes check	✅ Passed	The changes are focused solely on fixing JSON/CSV output serialization for host discovery scans in output.go and runner.go with no unrelated modifications.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing touches

• 📝 Generate docstrings

---

📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 39a50c1 and 8c75aa4.

📒 Files selected for processing (1)

• pkg/runner/runner.go

🚧 Files skipped from review as they are similar to previous changes (1)

• pkg/runner/runner.go

---

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[coderabbitai]

Actionable comments posted: 2

📜 Review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between b96cd90 and 39a50c1.

📒 Files selected for processing (2)

• pkg/runner/output.go
• pkg/runner/runner.go

🧰 Additional context used

🧬 Code graph analysis (1)

pkg/runner/output.go (2)

pkg/port/port.go (1)

• Port (10-17)

pkg/protocol/protocol.go (1)

• Protocol (7-7)

🔇 Additional comments (2)

pkg/runner/output.go (2)

210-217: LGTM! Host discovery JSON output correctly handled.

The zero-port case now properly marshals the result and writes it with a newline, ensuring JSON output is produced for host discovery scans where no ports are found.

---

276-286: LGTM! Host discovery CSV output correctly handled.

The zero-port case now writes a single CSV row using the pre-initialized data, ensuring CSV output is produced for host discovery scans. The else block maintains the existing per-port row emission for regular port scans.

[coderabbitai]

⚠️ Potential issue | 🟠 Major

Fix JSON formatting and error handling.

Two issues with the JSON console output for host discovery:

1. Line 1162 writes JSON bytes without a newline, inconsistent with the pattern used elsewhere (e.g., line 1085 uses fmt.Sprintf("%s\n", b)).
2. Line 1161 ignores the error from data.JSON(), which could hide marshaling failures.

🔎 Proposed fix

 if r.options.JSON {
-    b, _ := data.JSON(r.options.ExcludeOutputFields)
-    buffer.Write(b)
+    b, err := data.JSON(r.options.ExcludeOutputFields)
+    if err != nil {
+        gologger.Error().Msgf("Could not marshal JSON for %s: %s\n", host, err)
+        continue
+    }
+    buffer.Write([]byte(fmt.Sprintf("%s\n", b)))
     gologger.Silent().Msgf("%s", buffer.String())

🤖 Prompt for AI Agents

In pkg/runner/runner.go around lines 1160 to 1163, the JSON output to the
console neglects error handling from data.JSON(...) and writes bytes without a
trailing newline; change to capture and check the error returned by
data.JSON(r.options.ExcludeOutputFields), handle/report the error via gologger
(and avoid ignoring it), and when successful write the JSON bytes followed by a
newline (or use fmt.Sprintf("%s\n", b) / buffer.Write with an explicit '\n')
before calling gologger.Silent().Msgf so output formatting matches other JSON
paths.

[dogancanbakir]

Thanks for the PR, @sheikhshaheerimran habibi!

[sheikhshaheerimran]

@dogancanbakir Most welcome. I Iook forward to actively contribute to this project.