dry-options-pattern

name	dry-options-pattern
description	**Description:** Use when consolidating multiple similar formatting functions into one. Applies to any case where 2-3 functions share 80%+ logic but differ in output format or filtering.

DRY Options Pattern for Formatter Functions

Description: Use when consolidating multiple similar formatting functions into one. Applies to any case where 2-3 functions share 80%+ logic but differ in output format or filtering.

The Pattern

When you find multiple functions that:

• Read from the same data source
• Iterate the same way
• Differ only in formatting, filtering, or header/footer text

Consolidate into one function with an options object:

export interface CommandHelpOptions {
  /** Output format: 'verbose' shows full details; 'compact' is one-liner per item. */
  format?: 'verbose' | 'compact';
  /** Filter parameter — e.g., role-based filtering. */
  role?: string;
}

export function buildCommandHelp(options?: CommandHelpOptions): string {
  const format = options?.format ?? 'verbose';
  // ... shared logic with format-conditional branches
}

Applied Example: CommandHelp.ts

Before (3 functions):

• buildCommandHelp() — verbose, no role filter
• buildCommandReminder(role?) — compact, with role filter
• buildCommandReminderMessage(role?) — trivial wrapper

After (1 function):

• buildCommandHelp(options?) — format controls verbose/compact, role controls filtering
• Callers: buildCommandHelp() for errors, buildCommandHelp({ format: 'compact', role }) for reminders

Checklist

1. Identify shared data source and iteration logic
2. List the differences between functions (format, filtering, headers/footers)
3. Design options interface with sensible defaults (most common use = no args)
4. Move filtering logic inside the function gated by options
5. Update all callers — trivial wrappers become direct calls
6. Remove the duplicates entirely
7. Update tests to cover both format paths