klen/code-architecture-wrong-abstraction

Code Architecture: Avoiding Wrong Abstractions

Core Principle

Prefer duplication over the wrong abstraction. Wait for patterns to emerge before abstracting.

Premature abstraction creates confusing, hard-to-maintain code. Duplication is far cheaper to fix than unwinding a wrong abstraction.

The Rule of Three

Don't abstract until code appears in at least 3 places. This provides enough context to identify genuine patterns vs coincidental similarities.

// ✅ Correct: Wait for the pattern to emerge
// First occurrence - just write it
const userTotal = items.reduce((sum, item) => sum + item.price, 0);

// Second occurrence - still duplicate
const cartTotal = products.reduce((sum, p) => sum + p.price, 0);

// Third occurrence - NOW consider abstraction
const calculateTotal = (items, priceKey = 'price') =>
  items.reduce((sum, item) => sum + item[priceKey], 0);

When to Abstract

✅ Abstract When

• Same code appears in 3+ places
• Pattern has stabilized (requirements are clear)
• Abstraction simplifies understanding
• Use cases share identical behavior, not just similar structure

❌ Don't Abstract When

• Code only appears in 1-2 places
• Requirements are still evolving
• Use cases need different behaviors (even if structure looks similar)
• Abstraction would require parameters/conditionals for variations

The Wrong Abstraction Pattern

This is how wrong abstractions evolve:

// 1️⃣ Developer A spots duplication and extracts it
function processData(data) {
  return data.map(transform).filter(validate);
}

// 2️⃣ New requirement is "almost" compatible
function processData(data, options = {}) {
  let result = data.map(options.customTransform || transform);
  if (options.skipValidation) return result;
  return result.filter(options.customValidate || validate);
}

// 3️⃣ More variations pile up...
function processData(data, options = {}) {
  let result = data;
  if (options.preProcess) result = options.preProcess(result);
  result = result.map(options.customTransform || transform);
  if (!options.skipValidation) {
    result = result.filter(options.customValidate || validate);
  }
  if (options.postProcess) result = options.postProcess(result);
  if (options.sort) result = result.sort(options.sortFn);
  return options.limit ? result.slice(0, options.limit) : result;
}

// ❌ Now it's incomprehensible spaghetti

How to Fix Wrong Abstractions

The fastest way forward is back:

1. Inline the abstraction back into each caller
2. Delete the portions each caller doesn't need
3. Accept temporary duplication for clarity
4. Re-extract proper abstractions based on current understanding

// Before: One bloated function trying to do everything
processData(users, { customTransform: formatUser, skipValidation: true });
processData(orders, { sort: true, sortFn: byDate, limit: 10 });

// After: Inline and simplify each use case
const formattedUsers = users.map(formatUser);
const recentOrders = orders.sort(byDate).slice(0, 10);

// Later: If true patterns emerge, abstract properly

Hidden Costs of Abstraction

| Benefit | Hidden Cost | |---------|-------------| | Code reuse | Accidental coupling between unrelated modules | | Single source of truth | Layers of indirection obscure bugs | | DRY compliance | Organizational inertia makes refactoring painful |

Facade Pattern: When It Becomes a Wrong Abstraction

Facades wrap complex subsystems behind a simple interface. They're useful but often become wrong abstractions when overused.

The Typography Component Trap

// ❌ Facade that becomes limiting
<Typography variant="body" size="sm">Hello</Typography>

// What if you need <small> or <mark>?
// Now you must extend the facade first:
<Typography variant="body" size="sm" as="small">Hello</Typography>  // Added prop
<Typography variant="body" size="sm" as="mark">Hello</Typography>   // Another prop

// ❌ Facade keeps growing with every edge case
type TypographyProps = {
  variant: 'h1' | 'h2' | 'body' | 'caption';
  size: 'sm' | 'md' | 'lg';
  as?: 'p' | 'span' | 'small' | 'mark' | 'strong' | 'em';  // Growing...
  weight?: 'normal' | 'bold';
  color?: 'primary' | 'secondary' | 'muted';
  // ... more props for every HTML text feature
};

When Facade Works

// ✅ Good: Facade encapsulates complex logic
<DatePicker
  value={date}
  onChange={setDate}
  minDate={today}
/>
// Hides: localization, calendar rendering, keyboard nav, accessibility

// ✅ Good: Facade enforces design system constraints
<Button variant="primary" size="md">Submit</Button>
// Ensures consistent styling, no arbitrary colors

When to Skip the Facade

// ✅ Sometimes native HTML is clearer
<small className="text-muted">Fine print</small>
<mark>Highlighted text</mark>

// vs forcing everything through a facade:
<Typography variant="small" highlight>...</Typography>  // ❌ Overengineered

Facade Trade-offs

| Use Facade When | Skip Facade When | |-----------------|------------------| | Hiding complex logic (APIs, state) | Wrapping simple HTML elements | | Enforcing design constraints | One-off styling needs | | Team needs consistent patterns | Juniors need to learn the underlying tech | | Behavior is stable and well-defined | Requirements are still evolving |

The Junior Developer Test

If a junior must:

1. Learn the facade API
2. Then learn the underlying technology anyway
3. Then extend the facade for edge cases

...the facade adds friction, not value. Sometimes ctrl+f and manual updates across files is simpler than maintaining a leaky abstraction.

Quick Reference

DO

• Wait for 3+ occurrences before abstracting
• Let patterns emerge naturally
• Optimize for changeability, not DRY compliance
• Test concrete features, not abstractions
• Inline bad abstractions and start fresh

DON'T

• Abstract based on structural similarity alone
• Add parameters/conditionals to force fit new use cases
• Preserve abstractions due to sunk cost fallacy
• Fear temporary duplication

Key Philosophies

| Approach | Meaning | When to Use | |----------|---------|-------------| | DRY | Don't Repeat Yourself | After patterns stabilize | | WET | Write Everything Twice | Default starting point | | AHA | Avoid Hasty Abstractions | Guiding principle |

References

• The Wrong Abstraction - Sandi Metz
• The Wet Codebase - Dan Abramov
• AHA Programming - Kent C. Dodds