Duplicate Code: HTTP server runner onError handler (routerlicious-base)

[github-actions]

Analysis of commit 8fa20de

Assignee: @copilot

Summary

AlfredRunner, RiddlerRunner, and NexusRunner each implement an identical private onError(error) handler for the Node HTTP server "error" event. This is a clear copy/paste duplication (~26 lines) across 3 services that should be centralized to reduce maintenance and bug-fix drift.

Duplication Details

Pattern: identical HTTP listen error handling

• Severity: Medium

• Occurrences: 3

• Locations:

  • server/routerlicious/packages/routerlicious-base/src/alfred/runner.ts (lines 160-186)
  • server/routerlicious/packages/routerlicious-base/src/riddler/runner.ts (lines 125-151)
  • server/routerlicious/packages/routerlicious-base/src/nexus/runner.ts (lines 194-220)

• Code Sample (representative):

private onError(error) {
	if (!this.runnerMetric.isCompleted()) {
		this.runnerMetric.error(
			`${this.runnerMetric.eventName} encountered an error in http server`,
			error,
		);
	}
	if (error.syscall !== "listen") {
		throw error;
	}

	const bind = typeof this.port === "string" ? `Pipe ${this.port}` : `Port ${this.port}`;

	// Handle specific listen errors with friendly messages
	switch (error.code) {
		case "EACCES":
			this.runningDeferred?.reject(`${bind} requires elevated privileges`);
			this.runningDeferred = undefined;
			break;
		case "EADDRINUSE":
			this.runningDeferred?.reject(`${bind} is already in use`);
			this.runningDeferred = undefined;
			break;
		default:
			throw error;
	}
}

Impact Analysis

• Maintainability: Any changes to listen-error handling, logging, or metric reporting must be replicated across 3 runners.
• Bug Risk: High risk of inconsistent future behavior (e.g., adding a new error.code case or changing metric wording in only one runner).
• Code Bloat: ~75 lines of repeated logic across the codebase.

Refactoring Recommendations

1. Extract a shared helper in routerlicious-base, e.g. handleRunnerHttpServerError(...) or createListenErrorHandler(...).

   • Suggested location: server/routerlicious/packages/routerlicious-base/src/utils/runnerErrors.ts (or an existing shared util module)
   • Parameters likely needed: runnerMetric, runningDeferred, port
   • Benefits: single place to update logic and standardize logging/metrics.

2. (Optional) If runners already share other lifecycle helpers, consider a small base class or composition helper that wires httpServer.on("error") and delegates to the shared implementation.

Implementation Checklist

• Extract shared listen-error handler utility
• Replace onError implementations in Alfred/Riddler/Nexus with calls to the shared helper
• Ensure runnerMetric completion semantics remain unchanged
• Run routerlicious-base tests / service startup smoke checks

Analysis Metadata

• Analyzed Files: server/routerlicious/packages/routerlicious-base/src/{alfred,riddler,nexus}/runner.ts
• Detection Method: Serena semantic scan + duplicate-window detection
• Commit: 8fa20de
• Analysis Date: 2026-03-01T07:54:49.900Z

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