addyosmani/agent-skills/code-simplification

ASK BEFORE EVERY CHANGE:
→ Does this produce the same output for every input?
→ Does this maintain the same error behavior?
→ Does this preserve the same side effects and ordering?
→ Do all existing tests still pass without modification?

1. Read CLAUDE.md / project conventions
2. Study how neighboring code handles similar patterns
3. Match the project's style for:
   - Import ordering and module system
   - Function declaration style
   - Naming conventions
   - Error handling patterns
   - Type annotation depth

// UNCLEAR: Dense ternary chain
const label = isNew ? 'New' : isUpdated ? 'Updated' : isArchived ? 'Archived' : 'Active';
// CLEAR: Readable mapping
function getStatusLabel(item: Item): string {
  if (item.isNew) return 'New';
  if (item.isUpdated) return 'Updated';
  if (item.isArchived) return 'Archived';
  return 'Active';
}

// UNCLEAR: Chained reduces with inline logic
const result = items.reduce((acc, item) => ({
  ...acc,
  [item.id]: { ...acc[item.id], count: (acc[item.id]?.count ?? 0) + 1 }
}), {});
// CLEAR: Named intermediate step
const countById = new Map<string, number>();
for (const item of items) {
  countById.set(item.id, (countById.get(item.id) ?? 0) + 1);
}

BEFORE SIMPLIFYING, ANSWER:
- What is this code's responsibility?
- What calls it? What does it call?
- What are the edge cases and error paths?
- Are there tests that define the expected behavior?
- Why might it have been written this way? (Performance? Platform constraint? Historical reason?)
- Check git blame: what was the original context for this code?

FOR EACH SIMPLIFICATION:
1. Make the change
2. Run the test suite
3. If tests pass → commit (or continue to next simplification)
4. If tests fail → revert and reconsider

COMPARE BEFORE AND AFTER:
- Is the simplified version genuinely easier to understand?
- Did you introduce any new patterns inconsistent with the codebase?
- Is the diff clean and reviewable?
- Would a teammate approve this change?

// SIMPLIFY: Unnecessary async wrapper
// Before
async function getUser(id: string): Promise<User> {
  return await userService.findById(id);
}
// After
function getUser(id: string): Promise<User> {
  return userService.findById(id);
}
// SIMPLIFY: Verbose conditional assignment
// Before
let displayName: string;
if (user.nickname) {
  displayName = user.nickname;
} else {
  displayName = user.fullName;
}
// After
const displayName = user.nickname || user.fullName;
// SIMPLIFY: Manual array building
// Before
const activeUsers: User[] = [];
for (const user of users) {
  if (user.isActive) {
    activeUsers.push(user);
  }
}
// After
const activeUsers = users.filter((user) => user.isActive);
// SIMPLIFY: Redundant boolean return
// Before
function isValid(input: string): boolean {
  if (input.length > 0 && input.length < 100) {
    return true;
  }
  return false;
}
// After
function isValid(input: string): boolean {
  return input.length > 0 && input.length < 100;
}

# SIMPLIFY: Verbose dictionary building
# Before
result = {}
for item in items:
    result[item.id] = item.name
# After
result = {item.id: item.name for item in items}
# SIMPLIFY: Nested conditionals with early return
# Before
def process(data):
    if data is not None:
        if data.is_valid():
            if data.has_permission():
                return do_work(data)
            else:
                raise PermissionError("No permission")
        else:
            raise ValueError("Invalid data")
    else:
        raise TypeError("Data is None")
# After
def process(data):
    if data is None:
        raise TypeError("Data is None")
    if not data.is_valid():
        raise ValueError("Invalid data")
    if not data.has_permission():
        raise PermissionError("No permission")
    return do_work(data)

// SIMPLIFY: Verbose conditional rendering
// Before
function UserBadge({ user }: Props) {
  if (user.isAdmin) {
    return <Badge variant="admin">Admin</Badge>;
  } else {
    return <Badge variant="default">User</Badge>;
  }
}
// After
function UserBadge({ user }: Props) {
  const variant = user.isAdmin ? 'admin' : 'default';
  const label = user.isAdmin ? 'Admin' : 'User';
  return <Badge variant={variant}>{label}</Badge>;
}
// SIMPLIFY: Prop drilling through intermediate components
// Before — consider whether context or composition solves this better.
// This is a judgment call — flag it, don't auto-refactor.